ONIONS WITH HIGH STORAGE ABILITY, HIGH SOLUBLE SOLIDS CONTENT AND/OR LOW PUNGENCY

Abstract

Long-day onion plants, capable of producing onion bulbs comprising high soluble solids combined with a sweet taste as a result of low pungency, are provided, as are methods for producing such plants, bulbs and seeds. Such onions can be stored for long periods without a loss in quality and without an increase in pungency.

Claims

1-20. (canceled)

21. A long-day onion plant, or part or seed thereof, wherein said plant is of a variety that produces bulbs having (i) a mean Pyruvic Acid Development (PAD) measurement at harvest of less than 5.5 Mol pyruvate/g fresh weight (FW); and (ii) a storage decay of less than 10% after about 4 months, wherein the plant derives from onions designated I37853B, I37554A, or I37554B, a representative sample of seeds having been deposited under ATCC Accession Nos. PTA-9053, PTA-9054 and PTA-9055, respectively, wherein the storage decay is assessed by weighing non-decayed bulbs and comparing their weight to the total weight at the beginning of storage, and wherein the mean PAD measurement at harvest and storage decay is determined using bulbs from onion plants of the same variety and grown under the same environmental conditions.

22. The onion plant of claim 21, wherein said mean PAD measurement at harvest is less than 4.0 Mol pyruvate/g FW.

23. The onion plant of claim 21, wherein the mean PAD measurement after 5-6 months of storage is equal to or less than 3.75 Mol pyruvate/g FW.

24. The onion plant of claim 21, wherein said bulbs have a mean soluble solids content (SSC) at harvest of at least 8%.

25. The onion plant of claim 24, wherein said SSC is reduced by less than 2% after storage for at least 4 months.

26. The onion plant of claim 21, wherein said PAD measurement is reduced after storage compared to the PAD measurement at harvest.

27. The onion plant of claim 26, wherein the pungency level of the most pungent bulb and least pungent bulb differ by at most 4 Mol pyruvate/g FW.

28. The onion plant of claim 27, wherein all bulbs have a pungency between 1 and 4 Mol pyruvate/g FW.

29. A cell of the onion plant of claim 21.

30. A seed of the onion plant of claim 21 or part thereof, wherein said seed grows into a plant that produces bulbs having a mean PAD measurement at harvest of less than 4.5 Mol pyruvate/g fresh weight (FW).

31. A bulb of the onion plant of claim 21.

32. A container comprising a plurality of bulbs of claim 31.

33. A container comprising a plurality of bulbs, wherein at least 75% of the bulbs are bulbs of claim 31.

34. The container according to claim 33, wherein said container comprises at least 1 pound of bulbs.

35. A part of the onion plant of claim 21.

36. The part according to claim 35, wherein said part is a cell or cell culture, a tissue culture, a protoplast, an ovule, a leaf, pollen, an ovule, a meristem, an embryo, or a plant organ.

37. A part of a seed of claim 30.

38. A part of a bulb of claim 31.

39. A method for producing a long-day onion comprising crossing an onion plant of claim 21, with a second onion plant, and obtaining F1 seeds from said cross.

40. An onion produced by the method of claim 39 or part thereof, wherein the onion derives from onions designated I37853B, I37554A, or I37554B, a representative sample of seeds having been deposited under ATCC Accession Nos. PTA-9053, PTA-9054 and PTA-9055, respectively, is present in said onion; wherein said onion is of a variety that produces bulbs having (i) a mean Pyruvic Acid Development (PAD) measurement at harvest of less than 5.5 Mol pyruvate/g fresh weight (FW); and (ii) a storage decay of less than 10% after about 4 months, wherein the storage decay is assessed by weighing non-decayed bulbs and comparing their weight to the total weight at the beginning of storage; and wherein the mean PAD measurement at harvest and storage decay is determined using bulbs from onion plants of the same variety and grown under the same environmental conditions.

41. The plant part of claim 40, wherein said part is a cell or cell culture, a tissue culture, a protoplast, an ovule, a leaf, pollen, an ovule, a meristem, an embryo, or a plant organ.

42. A method for producing a long-day onion comprising crossing an F1 long-day onion plant with a second onion plant, and obtaining F2 seeds from said cross, wherein said F2 long-day onion plant is of a variety that produces bulbs having (i) a mean Pyruvic Acid Development (PAD) measurement at harvest of less than 5.5 Mol pyruvate/g fresh weight (FW); and (ii) a storage decay of less than 10% after about 4 months, wherein the F1 and F2 long-day onion plant derive from onions designated I37853B, I37554A, or I37554B, a representative sample of seeds having been deposited under ATCC Accession Nos. PTA-9053, PTA-9054 and PTA-9055, respectively, wherein the storage decay is assessed by weighing non-decayed bulbs and comparing their weight to the total weight at the beginning of storage; and wherein the mean PAD measurement at harvest and storage decay is determined using bulbs from onion plants of the same variety and grown under the same environmental conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION

Definitions

[0041] As used herein, the phrase to comprise and its conjugations is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. In addition, reference to an element by the recitation of a or an does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. Thus, a or an usually means at least one, e.g., a cell refers also to several cells in the form of cell cultures, tissues, whole organism, etc. Similarly, a bulb or a plant also refers to a plurality of bulbs and plants, respectively.

[0042] As used herein, the term plant includes the whole plant or any parts or derivatives thereof, such as plant organs (e.g., harvested or non-harvested storage organs, bulbs, tubers, fruits, leaves, etc.), plant cells, plant protoplasts, plant cell tissue cultures from which whole plants can be regenerated, plant calli, plant cell clumps, and plant cells that are intact in plants, or parts of plants, such as embryos, pollen, ovules, fruits (e.g., harvested tissues or organs), flowers, leaves, seeds, tubers, bulbs, clonally propagated plants, roots, stems, root tips and the like. Also any developmental stage is included, such as seedlings, immature and mature bulbs, etc.

[0043] Variety means a plant grouping within a single botanical taxon of the lowest known rank, which grouping, irrespective of whether the conditions for the grant of a breeder's right are fully met, can be defined by the expression of the characteristics resulting from a given genotype or combination of genotypes, distinguished from any other plant grouping by the expression of at least one of the said characteristics and considered as a unit with regard to its suitability for being propagated unchanged.

[0044] Phenotype is the observable external and/or physiological appearance of the plant as a result of the interaction between its genotype and its environment. It includes all observable morphological and physiological characteristics and thus encompasses phenotypes such as pungency, PAD measurements and soluble solid contents of onion bulbs.

[0045] Genotype is the total of inheritable genetic information of a plant, partly influenced by the environmental factors, which is expressed in the phenotype.

[0046] As used herein, Onion plant or onion is a plant of the botanical species Allium cepa L. or parts thereof, such as the (harvested) bulb, seeds, etc. Bulb is the harvested, edible portion of the plant. Onion bulbs may be developing or mature. Herein mature bulbs are preferred, which are bulbs ready for harvest or harvested.

[0047] Long-day onion plants will initiate bulb formation when light (day length) is at least about 14 contiguous hours or more, e.g., at least about 14, 15 or 16 hours. Preferably this contiguous light (hours per day) is provided for 2, 4, 7, 14, 21, 25 or more days to initiate bulb formation.

[0048] Storage conditions encompass typical conditions used to store (preferably fresh) onions, such as darkness, cool temperature (as used herein, a cool temperature means preferably below 12 C., e.g., about 3-12 C., 3-10 C., 5-10 C. or about 3-5 C., preferably about 3, 4 or 5 degrees Celsius) and a relative humidity (RH) of about 60-80%, preferably about 70-80%, most preferably around 70%. Also preferred is controlled ventilation.

[0049] A family is the progeny of one plant, which has been pollinated by a number of different other plants.

[0050] Hybrid or hybrid plant is a plant produced by the inter-crossing (cross-fertilization) of at least two different plants or plants of different parent lines. It is understood that the seeds of such a cross (hybrid seeds) are encompassed herein, as well as the hybrid plants grown from those seeds and plant parts derived from those grown plants (e.g. bulbs).

[0051] F1, F2, etc. refers to the consecutive related generations following a cross between two parent plants or parent lines. The plants grown from the seeds produced by crossing two plants or lines is called the F1 generation. Selfing the F1 plants results in the F2 generation, etc.

[0052] Soluble Solids or Soluble Solids Content (SSC herein), is the percentage (%) of water-soluble compounds in onion bulbs as measured by a refractometer according to the method of Mann and Hoyle, 1945 (Proc. Americ. Soc. Hort. Sci. 46: 285-292) or Foskett and Peterson, 1949 (Proc. Americ. Soc. Hort. Sci. 55: 314-318).

[0053] High SSC refers herein to an average SSC of a representative number of onion bulbs (e.g., at least 10, 15, 20, 30, 40, 50, 50, 60, 70, 80, 90 or more bulbs) of at least 7% or 7.5%, preferably at least 8%, 9%, 10%, 11%, 12%, 15%, 20%, 25%, 30% or more. Thus, average SSC of 7.5-30%, more preferably 8-20%, 8-15%, 10-20%, etc. are encompassed herein.

[0054] Pungency is the typical sharp taste of onion as the onion bulb tissue disintegrates by comminution. Pungency is preferably determined by measuring the enzymatic development of pyruvic acid according to the method of Schwimmer and Weston (1961, J. of Agric. Food Chemistry 9:301-304), which is strongly correlated to the flavour perception by a test panel (Schwimmer 1962, J. Food Sci. 27: 94-97; Wall and Corgan, 1992, Hort. Science 27: 1029-1030). Pungency is expressed as Mot (micromoles, also M or mol herein) per gram fresh weight bulb material (Mol/g FW). It is also referred to as PAD measurement (PAD from Pyruvic Acid Development) or pyruvate measurement or pyruvate level herein.

[0055] Low pungency refers herein to an average pungency of a representative number of (mature) onion bulbs (e.g., at least about 5, 8, 10, 15, 20, 30, 40, 50, 50, 60, 70, 80, 90 or more bulbs) of less than 5.5 Mol/g FW, preferably less than 5.0, 4.5, 4.0 Mol/g FW, more preferably equal to or less than 3.8 or 3.75 Mol/g FW, most preferably equal to or less than 3.5, 3.0, 2.5, 2.3, 2.0, 1.8, 1.5, or 1.3 Mol/g FW, as determined by PAD measurement. Thus, average pungencies of between 3.5 and 1.3 Mol/g FW, between 3.0 and 1.3 Mol/g FW, or between 3.0 and 2.0 Mol/g FW, etc. are encompassed herein.

[0056] A narrow pungency range refers to the variance in pungency between individual bulbs of a plurality of bulbs obtained from one plant line being narrow, i.e., the pungency level of the most pungent bulb (maximum value) and least pungent bulb (minimum value) differ preferably by less than or at most 5 Mol/g FW, more preferably less than or at most 4 Mol/g FW or less than or at most 3.5 Mol/g FW. Preferably the maximum pungency is less than 5 Mol/g FW. Preferred ranges of pungency within a plant line are, thus, that all bulbs have a pungency between 0 (min) and 5 (max) Mol/g FW, preferably between 1 (min) and 5 (max) Mol/g FW, more preferably between 1 (min) and 4 (max) Mol/g FW. Also, in one embodiment of the invention, all bulbs have a pungency from 0 (min) to 5 (max) Mol/g FW, preferably from 1 (min) to 5 (max) Mol/g FW, more preferably from 1 (min) to 4 (max) Mol/g FW. A narrow pungency range is an important quality characteristic for the consumer.

[0057] Long storage refers herein to a storage length of at least 2, 3, 4, 5, 6, 7 or more months. Preferably there is no significant increase in pungency and/or no significant reduction in SSC during the storage period, i.e., when comparing the average pungency and/or SSC at harvest (or shortly after harvest) with the pungency and/or SSC level after 2, 3, 4, 5, 6, 7 or more months of storage. No significant increase in pungency refers herein to an increase in pungency measurement (i.e., pyruvate) after the storage period by less than 10%, more preferably less than 5%, even more preferably less than 3%, 2% or 1%, more preferably no increase at all, and optionally even a reduction in pungency, compared to the measurement at harvest (or shortly after harvest). No significant reduction in SSC refers herein to a reduction in SSC levels after the storage period of less than 5%, 4%, 3% or 2%, preferably less than 1% or 0.5%, more preferably unchanged, compared to the SSC level at harvest (or shortly after harvest).

[0058] An onion plant (and seed of an onion plant, and parts derived from such a plant) requiring 14 or more contiguous hours of daylight to initiate bulb formation is provided, whereby the bulb has a low pungency, especially at harvest. Preferably the bulb also has a high soluble solid content (SSC), especially at harvest. The bulb substantially maintains pungency after storage for about 2, 3, 4, 5, 6, 7 or more months. The bulb also substantially maintains SSC content for about 2, 3, 4, 5, 6, 7 or more months.

[0059] In one aspect, the invention provides onion plants, bulbs and seeds, whereby the bulbs comprise a low (mean) pungency at harvest, a high (mean) SSC and/or a long storage ability. The (mean) pungency at harvest is preferably less than 5.5, 5.0, 4.5, 4.0 Mol/g FW, more preferably equal to or less than 3.8 or 3.75 Mol/g FW, preferably equal to or less than 3.5, 3.0, 2.5, 2.3, 2.0, 1.8, 1.5, 1.3 Mol/g FW or less. The (mean) SSC at harvest is preferably at least 7.5%, more preferably at least 8%, 9%, 10%, 11%, 12%, 15%, 20%, 25%, 30% or more. The bulbs according to the invention can be stored for at least 2, 3, 4, 5, 6, 7 or more months, preferably without any significant increase in pungency at the end of storage and/or without any significant reduction in SSC.

[0060] In addition, the onion plants provided herein produce bulbs which have a narrow pungency range as defined above. This characteristic is an important feature for the consumer of fresh onions, as often a bag of onions are bought but individual onions are used for the preparation of food. Thus, in one embodiment a plurality of (harvested) onion bulbs are provided which have a narrow pungency range, as are plants which are capable of producing such bulbs.

[0061] Also progeny of the above plants are provided (obtained by selfing or crossing), which retain bulbs with a low level of pungency, high SSC content and/or long storage ability. i.e. which are substantially identical to the bulbs of the parent(s) for these traits. Progeny include thus, for example inbred plants producing bulbs with one or more of the above traits or hybrid plants producing bulbs with one or more of the above traits.

[0062] Also parts of the above onion plants are provided. Such plant parts, derived from the onion plants described herein, may be a seed, a bulb, a leaf, a flower, pollen, stamen, an ovule, a cell, a protoplast, a tissue culture of cells or the like. A tissue culture of cells may, for example, be derived from a tissue selected from a leaf, pollen, embryo, bulb, flower, anther, pollen, ovule, bud, meristem or any cell.

[0063] In one aspect, the invention relates to long-day onion seeds deposited by Nunhems B.V. at the American Type Culture Collection (ATCC, 10801 University Boulevard, Manassas, Va. 20110-2209, USA) under the Budapest Treaty under accession number PTA-9053 (seeds of line I37853B), PTA-9054 (seeds of line I37554A) and PTA-9055 (seeds of line I37554B) on Mar. 13, 2008, or any derivatives thereof, such as progeny obtained by selfing any one of the deposited plants or by crossing of any one of the deposited plants with another onion plant. In one aspect, derivatives include inbred onion plants which comprise the low pungency, high SSC and/or long storage ability as described. In another aspect, derivatives include onion plants or seeds (and bulbs) obtained from using one of these lines (I37554A or B, 137853 or a derivative of any of these) as parent in one or more crosses with a further onion plant and/or one or more selfings, whereby the progeny have the same (or better) low pungency, high soluble solid phenotypes and/or storage properties as defined above and/or as the deposited lines. Therefore, derivatives may include hybrid onion plants or seeds (and bulbs of such plants) which produce/are capable of producing bulbs having the above (or better) low pungency, high SSC and/or long term storage abilities as described above and/or as the bulbs of 137853 and/or I37554A or B. Derivatives of the hybrids are also encompassed herein. In another aspect, hybrid seeds, plants and bulbs obtainable from crossing 137853 (or a derivative thereof, such as an inbred) with I37554A or B (or a derivative thereof, such as an inbred) are provided, as well as plants, bulbs and seeds obtained from using such F1 hybrids in further selfings or crosses. Therefore, various long day onion plants having low pungency, high SSC and/or long term storage ability are encompassed herein, including, for example, plants comprising the physiological and morphological characteristics of 137853 and/or I37554A or B.

[0064] Thus, a long day onion plant derived from, or derivable from, one of the plants deposited under Accession number PTA-9053, PTA-9054 or PTA-9055 by selfing, crossing, clonal propagation, or tissue culture is provided herein, wherein the plant produces onion bulbs having the same (or better) low pungency, high soluble solid phenotypes and/or storage properties (at harvest and/or after storage) as described herein and/or as the deposited lines PTA-9053, PTA-9054 or PTA-9055.

[0065] Progeny of the onion plants deposited under PTA-9053, PTA-9054 and PTA-9055 are provided, wherein said progeny produces onion bulbs having the same (or better) low pungency, high soluble solid phenotypes and/or storage properties (at harvest and/or after storage) as described herein and/or as the deposited lines PTA-9053, PTA-9054 or PTA-9055.

[0066] Derivatives also include plants obtained from tissue culture methods and tissue cultures themselves, whereby tissue of any of the herein described plants is used (e.g. leaf, pollen, flowers, embryos, protoplasts, etc.). Likewise, transgenic onions of any of the above plants are encompassed herein. Thus, onion plants into which one or more genetic elements have been introduced by transformation are also encompassed herein. Transformation and regeneration of onion uses methods known in the art. For example, one or more genes for herbicide resistance or resistance against microorganisms may be introduced. Likewise, transgenes may be introduced into the onions according to the invention by crossing the onion plant with a plant comprising the transgene(s) and selecting offspring comprising the transgene(s).

[0067] Preferably there is no significant increase in pungency and/or no significant reduction in SSC during the storage period of the bulbs, i.e., when comparing the average pungency and/or average SSC at harvest (or shortly after harvest) with the average pungency and/or average SSC level after 2, 3, 4, 5, 6, 7 or more months of storage. No significant increase in pungency refers herein to an increase in pungency measurement (i.e., pyruvate) after the storage period by less than 10%, preferably less than 5%, more preferably less than 3%, 2% or 1%, more preferably no increase at all, and optionally even a reduction in pungency, compared to the measurement at harvest (or shortly after harvest). A reduction in pungency compared to pungency at harvest includes, for example, a reduction by at least 0.5%, 1% or more. No significant reduction in SSC refers herein to a reduction in SSC levels after the storage period of less than 2%, preferably less than 1% or 0.5%, more preferably unchanged, compared to the SSC level at harvest (or shortly after harvest).

[0068] Also the pungency range preferably remains narrow during storage. In addition, decay after at least 2, 3, 4, 5, 6, 7 or more months of storage (as can be measured visually and/or by weight, e.g., weighing non-decayed bulbs and comparing their weight to the total weight at the beginning of storage), is low, i.e., at any given time-point, e.g., after about 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5 or 6 months of storage or more, decay is less than 10%, preferably less than 9%, 8%, 7.2%, 7%, 6%, 5%, 4%, 3%, 2%, 1% or even less.

[0069] The onion plants, bulbs and seeds are long-day onions, i.e., the plants initiate bulb formation under long periods of contiguous light, e.g. artificial or natural light of at least about 14 hours or more. The onion plant thus preferably requires 14 or more hours per day (per 24 hours) of contiguous light in order to initiate bulb formation.

[0070] In one aspect, the onion plants, or seeds provided herein are capable of forming bulbs which have a pungency of less than 3.75/g FW, preferably equal to or less than 3.5, 3.0, 2.5, 2.3, 2.0, 1.8, 1.5, 1.3 Mol/g FW when measured 2, 3, 4, 5, 6 or 7 months after harvest, e.g. after 5-6 months of storage in the dark, under cool temperatures and at a RH of 60-80%. These bulbs have a significantly lower average pungency than bulbs of seeds deposited under NCIMB Accession numbers 41329 and 41330 (described in WO2007/011857), as well as preferably a narrower pungency range than various onion lines described in WO2007/011857. In addition, the bulbs have at least an equivalent, preferably a significantly higher average SSC content than bulbs of seeds deposited under NCIMB Accession numbers 41329 and 41330 and/or a longer storage ability compared to such bulbs.

[0071] It was found that bulbs and plants having very low pungency and high SSC content can be selected for, which was believed to be impossible. Without limiting the invention, it is thought that the genetic linkage between one or more regions responsible for high pungency and regions responsible for high SSC can, contrary to prior belief, be broken, enabling the selection or identification of low pungency/high SSC plants. Plants provided herein can be made as described in the methods and Examples herein below, using breeding and selection methods (PAD measurements, SSC measurements and/or storage decay measurements and the like). Also seeds provided herein can be used to make plants according to the invention, as the traits can be transferred from the deposited seeds to other onion plants by crossing and selection. Basically the traits (low pungency, high SSC and/or long storage ability) can be introduced into any long day onion, such as for example Spanish onions, Spanish-type onions, (northern) yellow-type onions, white and red type onions, hard-globe eastern or western type onions, etc. Onion plants (e.g., open pollinated or hybrid plants) can therefore be made having these traits and having good agronomic characteristics, such as disease resistance (e.g. Fusarium resistance), pink root resistance, bulb size, % single centers, bolting tolerance, etc.

[0072] Also provided herein are containers comprising a plurality of onion bulbs having the above phenotypes, as well as containers comprising a plurality of onion seeds of the above plants or containers comprising a plurality of onion plants or seedlings. Containers may be of any type, such as bags, cans, tins, trays, boxes, flats and the like. Also provided herein are containers comprising onion bulbs having an average PAD measurement of less than about 5.5 Mol/g FW, preferably less than 3.75, 3.5, 3.0, etc. Mol/g FW, high SSC and/or long storage ability (each phenotype as defined above). Preferably in a container at least 75%, 85%, 95%, 98% or more of the bulbs have such a PAD measurement, SSC level and/or storage ability. Also, preferably the pungency range of all bulbs in a container is narrow. A container preferably contains at least about 1 pound, 5 pounds, 10 pounds or more bulbs. The container may be in any location, e.g., a store (such as a grocery store), warehouse, market place, distributor, etc.

[0073] Seed containers comprising seeds of an onion plant requiring 14 or more hours contiguous light to initiate bulb formation, wherein the seed is capable of producing an onion plant having a bulb comprising low pungency (i.e., a PAD measurement as defined), high SSC and/or long storage ability (also as defined) are also provided. Preferably the onion bulbs from greater than 50%, more preferably from greater than 60%, 70%, 75%, 80%, 90%, 95%, 98% of the plants produced by such seeds produce bulbs having an average PAD measurement of less than 5.5 Mol/g FW, preferably less than 5.0, 4.0, 3.5, or 3.0 Mol/g FW, etc., high SSC and/or long storage ability. The containers preferably comprise at least 100, 500, 1000, 10.000 or more seeds and is preferably selected from a bag, box, packet, tin or can. Also, preferably the pungency range of all bulbs derivable from the seeds in a container is narrow.

[0074] In another aspect, a method for producing an onion plant or seed, or a group of plants or seeds, is provided, whereby the plant, or group of plants, produce(s) a bulb after exposure to at least about 14 hours light per day (during a period of at least about 1 or more weeks, e.g., 2 or 3 or more weeks) which comprises a (single bulb or mean) pungency of less than 5.5, 5.0, 4.0, 3.75 Mol/g FW at harvest (or less, as defined above) and a (single bulb or mean) SSC at harvest of at least 7.5% or more (as defined above). Preferably, the bulbs retain low pungency and high SSC during storage. Also, the pungency range of the bulbs is preferably narrow. The method comprises crossing two parent onion plants or selfing an onion plant and harvesting the resulting onion seeds from the cross or selfing, wherein at least one parent is an onion plant as described above, or a derivative thereof. Seeds produced by the method are also provided herein, as are onion plants produced by growing those seeds and onion bulbs harvested from those grown plants.

[0075] The method may further comprise the step of growing an F1 hybrid onion plant obtained from seed obtained from said cross, crossing the F1 onion plant to another onion plant, e.g., to one of the parents used, and selecting progeny onion plants having the desired low pungency and high SSC content.

[0076] In a further aspect, a method for producing an onion plant or seed or a group of onion plants or seeds, is provided, whereby the plant, or group of plants, produce(s) (a) bulb(s) after exposure to at least about 14 hours light per day (during a period of at least about 1 or more weeks, e.g., 2 or 3 or more weeks) which comprises a (single bulb or mean) pungency of less than 5.5, 5.0, 4.0, 3.75 Mol/g FW at harvest (or less, as defined above) and a (single bulb or mean) SSC at harvest of at least 7.0 or 7.5% or more (as defined above). Preferably, the bulbs retain low pungency and high SSC during storage, show little decay during storage and/or have a narrow pungency range (all as described). The method comprises the steps of: [0077] a) crossing an onion plant producing bulbs having a low SSC and low pungency with an onion plant producing bulbs having a high SSC and high pungency, [0078] b) obtaining the F1 seeds from said cross, [0079] c) selfing and/or crossing the plants obtained from the F1 seeds one or more times with one another or with other onion plants, and [0080] d) identifying and selecting progeny plants which produce bulbs having a low pungency and high SSC by phenotyping the bulbs.

[0081] Optionally steps c) and/or d) can be repeated several times. Crossing in step c) may also involve backcrossing. In step d), plants having a narrow pungency range and/or plants showing little decay during storage may be selected. Thus, pungency range and/or storage ability can also be used as selection criteria in addition to or as an alternative of low pungency and/or high SSC. The same applies to the methods described herein below, even if only SSC and pungency are mentioned.

[0082] The phenotyping preferably involves determining the pungency, SSC content and/or storage ability (e.g. percentage decay after a certain storage period, which can be analysed visually) of the bulbs (e.g. by phenotyping one or more populations of step c) above) and selecting rare recombinants or mutants which have a low pungency and/or high SSC and/or long storage ability. The plants used under a) may be commercially available onion cultivars or breeding lines, such as long day onions and short day onions. Phenotyping can be carried out on a plurality of single bulbs independently, preferably grown under the same conditions next to suitable controls, or on a sample composed of (all or parts of) several bulbs. When single bulbs are used, preferably the mean value is calculated from a representative number of bulbs. Phenotyping can be done one or more times. For example PAD measurements and/or SSC measurements may be carried out at harvest and after 1, 2, 3, 4 or more weeks of storage or 2, 3, 4, 5, 6, 7, 8, 9 or more months of storage. In one embodiment the phenotyping (PAD and/or SSC measurements) is carried out after about 5, 6 or 7 months of storage (e.g. after about 150-210 days, e.g. about 150 days, 180 days, 200 days or 205, 206, 207, 208, 209, 210 days of storage). Phenotyping can be carried out at one or more steps of a breeding scheme.

[0083] Phenotyping may also comprise an analysis of the photoperiod response and selection of plants having a long-day response, so that in step d) long day onions are produced.

[0084] In one aspect a method for making long-day onion plants comprising a low pungency and high SSC, is provided, comprising a) (optionally) analysing onion bulbs for pungency and SSC, b) crossing plants producing bulbs having a high pungency and high SSC with plants producing bulbs with a low pungency and low SSC to produce F1 hybrids, c) selfing and/or (back)crossing F1 hybrid plants one or more times and d) selecting progeny plants for low pungency and high SSC content (at harvest and/or after storage) and preferably also for having a long day length photoperiod response and/or preferably also for having a narrow pungency range and e) selecting a long day onion plant producing bulbs having low pungency and high SSC, with levels similar to those of lines PTA-9053, PTA-9054 or PTA-9055 at harvest and/or after storage. Step d) involves pungency and SSC analysis at harvest and/or after storage. In the initial cross, the low pungency, low SSC onion parent may be a short-day onion variety, cultivar or breeding line and the high pungency, high SSC may be a long day onion variety, cultivar or breeding line. Preferably steps c) and d) are repeated several times, so that several cycles of phenotypic recurrent selection are carried out, leading to long day onions of step e).

[0085] In yet a further aspect, a method of producing an inbred, long-day onion plant comprising low pungency and high SSC is provided herein, comprising the steps of: [0086] a) the creation of variable populations of Allium cepa comprising the steps of crossing a plant or plants producing bulbs with low pungency and high SSC (as described herein) with a plant of the species Allium cepa, [0087] b) harvesting the F1 seed from any of the plants used in the cross of a) and growing F1 plants from the seed harvested, [0088] c) selfing the plants grown under b) or crossing these plants amongst one another, or crossing these plants with plants of Allium cepa, [0089] d) growing plants from the resulting seed harvested under normal plant growing conditions and, [0090] e) selecting plants producing bulbs having low pungency and high SSC, followed by selfing the selected plants, and optionally [0091] f) repeating the steps d) and/or e) until the inbred lines are obtained which are homozygous and can be used as parents in the production of hybrids having low pungency and high SSC.

[0092] Also provided is a method for developing male sterile inbred lines with the properties of low pungency and high SSC comprising the steps of crossing the plants of the inbred lines described above with plants of male sterile lines of Allium cepa and the subsequent selection and recurrent back crossing with the male fertile parent until the new male sterile line is genetically and phenotypically similar to the male fertile recurrent parent inbred line and has the combination of low pungency and high SSC.

[0093] The male sterile inbred line may be crossed with a male fertile inbred line resulting in hybrid seeds, whereby the plants grown therefrom possess the properties of low pungency and high SSC.

[0094] Likewise open pollinated, long-day onion plants comprising low pungency and high SSC can be made. Thus, onion plants according to the invention may be maintained as open pollinated lines, half-sib lines, male sterile lines, female sterile lines, etc. Male sterile inbred lines of onion plants according to the invention are useful as parents for producing hybrids.

[0095] In another aspect, a method for producing an onion crop from onion seeds or plants according to the invention and long day onions harvested therefrom is provided.

[0096] The following non-limiting examples illustrate the production of onion plants, seeds and bulbs according to the invention. All references mentioned herein are incorporated by reference.

EXAMPLES

Example 1Plant Development

[0097] Plants have been obtained by a long term breeding program (Oregon, USA) in which numerous plants have been analyzed for the desired combination of the traits as mentioned.

[0098] The initial cross concerned low pungency/low SSC onion plants (the commercially available long-day variety Ailsa Craig) with high pungency/high SSC long-day onion plants of a breeding line designated I37787B and subsequent selfing of the F1 plants to create variable F2 populations. No Spanish background was used.

[0099] A selected F2 individual (phenotyped for pungency and SSC) was crossed to an individual selected from a breeding line derived from the variety Oregon Danvers Yellow Globe. Plants from this cross where selfed and selected individuals from this progeny were selfed again. A low pungency, high SSC line was obtained and designated 137554.

[0100] Six additional cycles of phenotypic recurrent selection were made, with selection for the phenotypes high SSC and low pungency and having all desirable agronomic traits and long day length photoperiod response. High SSC was determined using refractometry analysis according to the method of Mann and Hoyle, 1945 (Proc. Americ. Soc. Hort. Sci. 46: 285-292) or Foskett and Peterson, 1949 (Proc. Americ. Soc. Hort. Sci. 55: 314-318). Pungency was determined using the PAD measurement of Schwimmer and Weston 1961 (supra). Throughout the scheme plants in each generation were selected after approximately 150 days of storage, i.e., PAD and/or SSC measurements were made after about 5 to 6 months of storage for selection purposes.

[0101] Coincident with the six cycles of phenotypic recurrent selection the selected plants were crossed and backcrossed to cytoplasmic/nuclear male sterile plants. In this way inbred maintainer line I37554B and its male sterile companion line I37554A were developed, both of which have lower pungency and higher SSC at harvest and after storage and are long day onions. Seeds of 137554 (I37554A and I37554B) have been deposited at the ATCC under the Budapest Treaty under accession number PTA-9054 and PTA-9055, respectively.

[0102] Line I37853B was developed by further breeding and selection with the above material and seeds of I37853B were deposited at the ATCC under the Budapest Treaty under accession number PTA-9053. Line I37853B has even lower pungency than I37554A and B and has improved bulb quality.

[0103] From these plants parent lines for producing hybrid varieties have been developed by additional crossing and further inbreeding while selecting for agronomic traits and good combining ability. The hybrid varieties produced with these lines have been evaluated for the unique combination of low pungency/high soluble solids, long storage and other desirable agronomic characteristics.

[0104] In one aspect of the invention, novel plants, seeds and bulbs of long-day onion I37554A or B and of I37853B are provided. Also, hybrids produced from crossing I37554A or B and I37853B are provided, as well as plants produced from such crosses or selfings and which produce bulbs comprising low pungency, high SSC and/or high storage capabilities.

Example 2Plant 137554 Having Low Pungency and High SSC

[0105] Table 1 below shows (average) pungency measured as pyruvate concentration in Mol/g FW and SSC content (%) of bulbs of the plant designated I37554A and the commercially available Long Day variety Granero 9536, both at harvest and during 3 months of storage.

TABLE-US-00001 TABLE 1 Pyruvate (Mol/g FW) SSC (%) Time Period* Granero I37554 Granero I37554 1 6.22 4.92 8.6 8.3 2 5.95 5.34 9.3 8.5 3 5.91 5.5 9.7 8.9 4 6.92 6.17 8.3 8.1 5 8.66 5.78 9.4 8.1 6 9.07 3.33 8.4 8.2 7 8.53 4.89 8.1 7.5 8 9.97 4.62 8.5 7.4 *The time periods are approximately two weeks apart.

[0106] The Example shows that during storage pyruvate levels of Granero, a long day Spanish hybrid variety which is pungent and has high SSC, increases significantly, while the pungency of I37554A does not change significantly and the SSC levels remain high and constant. Also, at harvest I37554A, combines low pungency with high SSC (and long day characteristics).

Example 3

[0107] Table 2 shows yield and percent storage decay of I37554A compared to commercial pungent and high SSC varieties Granero and Nebula (136 days after harvest, i.e., after about 4.5 months of storage). Percent decay was assessed by weight.

TABLE-US-00002 TABLE 2 Storage decay Weight No Yield (lbs/acre - 100's) Weight/bulb Decay decay Plant Total Large Medium Small (g) (%) (%) I37554A 595 401 134 14.5 179.5 7.1 92.9 Granero 680 539 104 3.5 225.0 5.5 94.5 Nebula 380 169 182 11.4 142.7 3.4 96.6

[0108] The Example shows that, while having low pungency, line I37554A has similar, good storage characteristics as known pungent storage onions which have high SSC.

Example 4

[0109] Table 3 shows pungency and SSC data for I37554B after more than 6 months (207 days, i.e., 6.9 months) of storage. Table 3 shows data for 92 single bulbs of I37554B and the mean.

TABLE-US-00003 TABLE 3 Pungency Plot number (Mol/g FW) SSC (%) 6111 2.52 9.20 6111 4.15 10.20 6111 2.70 9.20 6111 3.63 9.20 6111 2.62 9.80 6111 3.22 8.80 6111 4.37 8.80 6111 2.41 10.20 6111 3.56 10.20 6111 3.57 8.20 6111 3.03 7.80 6111 4.50 10.20 6111 3.88 10.20 6111 2.77 7.60 6111 3.48 9.20 6111 3.42 9.00 6111 3.54 10.40 6111 2.82 9.20 6111 4.41 10.80 6111 1.90 9.40 6111 2.86 9.80 6111 2.67 9.40 6111 3.29 9.80 6111 2.69 8.80 6111 4.03 9.00 6111 2.86 8.80 6111 2.76 8.80 6111 3.04 8.40 6111 3.50 9.40 6111 4.29 9.40 6111 4.13 7.80 6111 3.25 8.60 6111 2.05 9.80 6111 3.93 10.20 6111 3.42 9.80 6111 3.56 10.40 6111 3.15 8.20 6111 3.59 10.20 6111 2.86 10.20 6111 3.16 10.20 6111 2.36 8.60 6111 4.15 10.80 6111 3.20 9.00 6111 2.49 9.40 6111 3.35 10.80 6111 4.47 10.60 6111 3.87 9.80 6111 3.87 9.60 6111 4.17 10.40 6111 2.59 9.80 6111 1.29 10.20 6111 4.08 9.60 6111 3.25 8.80 6111 2.43 8.60 6111 3.10 9.40 6111 4.54 8.20 6111 4.12 9.80 6111 3.57 10.40 6111 3.62 10.40 6111 3.09 8.40 6111 2.92 9.00 6111 4.44 10.20 6111 1.76 9.80 6111 4.39 9.80 6111 3.23 10.40 6111 3.69 10.20 6111 4.20 11.20 6111 4.35 9.40 6111 4.29 10.40 6111 4.14 10.20 6111 4.43 10.20 6111 3.97 10.20 6111 3.72 10.40 6111 3.53 10.40 6111 4.17 11.60 6111 3.67 10.20 6111 4.30 10.00 6111 3.41 9.40 6111 4.17 9.80 6111 2.85 9.00 6111 4.74 9.80 6111 3.14 9.80 6111 4.17 10.00 6111 3.80 11.20 6111 3.83 10.20 6111 3.75 10.20 6111 2.84 9.80 6111 4.32 9.40 6111 4.63 10.40 6111 3.04 9.60 6111 3.78 10.00 6111 4.84 9.80 MEAN 3.5 9.67

[0110] The data show that line I37554B has low pungency and high SSC levels. Even after more than 6 months of storage the average pungency remains very low and average SSC remains high. Also, the pungency range is narrow (min. 1.29, max. 4.85).

Example 5Line I37853B

[0111] Table 4 shows single bulb pungency levels of line I37853B after 5-6 months of storage showing that very low pungency (mean pungency 2.3 Mol/g FW) has been achieved, combined with high SSC.

TABLE-US-00004 TABLE 4 Pungency (Mol/g FW) 1.3 1.4 3.7 4.7 3.3 2.3 3.1 2.1 3.0 2.0 2.6 2.1 2.4 1.6 2.4 2.3 2.2 3.0 1.2 2.6 1.9 2.1 3.6 2.0 1.8 2.0 3.0 1.3 2.1 1.8 1.3 2.4 2.2 2.5 1.9 2.0 3.7 1.9 Mean (38 bulbs) = 2.3

Example 6Hybrids

[0112] To generate hybrids of long day storage onions having low pungency and high SSC at harvest and after long term storage, line I37554A (female parent) was crossed with I37853B (male parent) to generate F1 hybrid seeds. The hybrids will be grown at various locations and pyruvate and SSC levels will be assessed and compared to the parents and high pungency lines or cultivars.

Example 7Line I37853B

[0113] Table 5 shows average pungency (pyruvate Mol/g FW), SSC (%) and Storage Decay (%) of line I37554B after storage (132 days after harvest).

TABLE-US-00005 TABLE 5 Pyruvate Storage Decay Name (Mol/g FW) SSC (%) (%) No decay (%) I37554B 3.8 8.6 9.1 90.9