Avocado rootstock named ‘Merensky 5’

Abstract

A new avocado variety, Merensky 5 has high tolerance to salinity and to Phytophthora cinnamomi when used as a rootstock. Hass trees grafted onto the Merensky 5 rootstock bear good yields.

Claims

1. A new and distinct rootstock variety of avocado tree having the characteristics as described and illustrated herein.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying photographs show specimens of the tree and plant parts of the new Merensky 5 variety.

(2) FIG. 1 is a photograph of a two-year-old, top-worked tree of the Merensky 5 variety on Merensky 2 rootstock, growing in Tzaneen, Limpopo Province, South Africa;

(3) FIG. 2 is a photograph depicting typical mature foliage of the Merensky 5 variety, with a ruler, in centimeters, below for size reference;

(4) FIG. 3 is a photograph depicting typical flush foliage of the Merensky 5 variety, with size reference ruler below;

(5) FIG. 4 is a photograph depicting typical inflorescence of the Merensky 5 variety, with a ruler below for size reference;

(6) FIG. 5 is a photograph depicting a typical external view of the fruit of the Merensky 5 variety, adjacent a ruler for size comparison; and

(7) FIG. 6 is a photograph depicting internal views of the fruit of the Merensky 5 variety, with and without the seed, respectively, adjacent to a ruler for size reference.

DETAILED BOTANICAL DESCRIPTION OF THE VARIETY

(8) The following is a detailed description of the new Merensky 5 variety, which was taken from approximately 4-year-old mature trees, with the exception as a rootstock for a specific scion when reference is made to root rot and salt tolerance as well as yield. The trees are located in an experimental orchard at Tzaneen, Limpopo Province, South Africa, and are grafted on a Merensky 2 rootstock.

(9) In those instances where precise color assessment could be made, The Royal Horticulture Society (R.H.S.) color numbering system (R.H.S. Colour Chart published by The Royal Horticultural Society, London 2001) is used herein for the color description of the rind, seed, bark, leaf, flower, flesh color and other characters of the Merensky 5 avocado tree. In other instances, generally, color terms are used in accordance with an ordinary dictionary significance.

(10) With reference to FIG. 1, the growth habit of the Merensky 5 variety is spreading. Table 1 below is data on the vigor of the Hass grafted onto the rootstock of the Merensky 5 as determined by trunk diameter measurements, taken 5 cm above the soil line, from trees planted in an orchard with negligible Phytophthora cinnamomi and salinity levels in Goleta, Calif., USA.

(11) TABLE-US-00001 TABLE 1 Trunk diameter (cm) Rootstock Year 2 Year 3 Year 4 Merensky 5 5.39 8.37 9.74 Merensky 2 4.15 8.37 9.09 Goleta, California, USA, with Hass scion (n = 15)

(12) Below in Table 2 are data of the vigor of the Hass grafted onto the rootstock of Merensky 5 as determined by trunk diameter measurements, taken 20 cm above the soil line, from trees planted in an orchard with Phytophthora cinnamomi and no salt in Tzaneen, Limpopo Province, South Africa.

(13) TABLE-US-00002 TABLE 2 Trunk diameter (cm) Rootstock Year 2 Year 3 Year 4 Merensky 5 2.67 3.21 3.94 Merensky 2 3.13 3.91 5.19 Tzaneen, Limpopo Province, South Africa, with Hass scion (n = 30)

(14) Table 3 below illustrates the data on the typical canopy size of Hass grafted onto the rootstock of Merensky 5 as determined by canopy volume measurements from trees planted in an orchard with negligible Phytophthora cinnamomi and salinity levels (Goleta, Calif., USA).

(15) TABLE-US-00003 TABLE 3 Canopy volume (m.sup.3) Rootstock Year 2 Year 3 Year 4 Merensky 5 0.45 0.68 0.76 Merensky 2 0.38 0.61 0.68 Goleta, California, USA, with Hass scion (n = 15)

(16) Table 4 below, for comparison, is data on the typical canopy size of Hass grafted onto the rootstock of Merensky 5 as determined by canopy volume measurements from trees in an orchard with Phytophthora cinnamomi and no salt (Tzaneen, Limpopo Province, South Africa).

(17) TABLE-US-00004 TABLE 4 Canopy volume (m.sup.3) Rootstock Year 3 Year 4 Merensky 5 0.29 0.34 Merensky 2 0.33 0.42 Tzaneen, Limpopo Province, South Africa, with Hass scion (n = 30)

(18) With reference to FIGS. 2-4, the color of a one-year-old branch is yellow-green (RHS 144A). The bark of the one-year-old branch is smooth. The lenticels of the one-year old branch are inconspicuous.

(19) The main stem is grey-brown (RHS 199C). The texture of the bark of the main stem is corky.

(20) The young shoot (flush) of the Merensky 5 has a medium intensity of anthocyanin coloration. The color of the flush is greyed-orange (RHS 165A). The conspicuousness of the lenticels is high. The lenticels are greyed-purple (RHS 85B). By comparison, lenticels in Duke 7 are green (RHS 139B). The lenticels are approximately 1.0 mm long. The lenticels have a concentration of +/15 lenticels per square cm. The upper side of the young leaves is a yellow-green (RHS 152A) color. The upper side of the young leaves has a high glossiness. The color of the lower surface of the young leaves is grey-brown (RHS 199A).

(21) A mature leaf has a length of approximately 15.3 cm and a width of approximately 6.3 cm. This provides a ratio of 2.4 length/width. The shape of the mature leaf is lanceolate. The color of the upper side of the mature leaf is yellow-green (RHS 147A). The upper side of the mature leaf has a medium glossiness. The color of the lower side of the mature leaf is green (RHS N138C). The veins on the lower side of the mature leaf are prominent and in relief. The color of the veins of the mature leaf are yellow-green (RHS 151A). The general shape and cross-section of a mature leaf is concave. Reflexing of apex in the mature leaf is present. The color of the petiole of the mature leaf is yellow-green (RHS 144B). The mature leaf has a medium anise aroma. The margin of the mature leaf has a medium undulation, and an acute leaf apex shape. The leaf base shape is acute. The length of the leaf petiole is approximately 3.7 cm. The leaves are held horizontally, i.e. approximately perpendicular to the shoot.

(22) With particular reference to FIG. 4, the flower of the Merensky 5 will now be described. The flower has a bud size of approximately 5 mm in length and approximately 4 mm in diameter. The bud shape is ovoid. The bud color is yellow-green (RHS 145A). The flower belongs to Group B, with the female opening occurring in the afternoon and the male opening the next morning. The flower's opening cycle lasts 20-24 hours. The petals are borne in two whorls of three perianth lobes. The petals possess entire margins and petal coloration is yellow-green (RHS 145C). There are commonly nine fertile stamens, with each having two basal orange nectar glands and three staminodia. The anthers are tetrathecal. The single pistil with a slender style and small stigmatic surface has one carpel with one ovule. The ovary is superior. The pedicel is commonly approximately 5 mm in length and approximately 1.5 mm in diameter. The coloration of the pedicel is yellow-green (RHS 145B). There are approximately 80-120 flowers per inflorescence. Generally, the Merensky 5 has been found to bloom in July-August at Tzaneen, Limpopo Province, South Africa. However, the flowering time in California, USA, is typically March-April.

(23) With reference now to FIGS. 5 and 6, the fruit and seed of the Merensky 5 variety will now be described. The fruit is typically 7.0 cm in length and approximately 5.6 cm in width, providing a length/width ratio of 1.3. The shape of the fruit is obovate. The color of the skin of the fruit, when ripe, is yellow-green (RHS 146A). The skin texture is smooth. There are no longitudinal ridges. The skin is very thin. The skin adherence to the flesh is weak. The main color of the flesh is yellow-green (RHS 154D). The color of intensely colored area of flesh next to the skin is yellow-green (RHS 144A). The width of the intensely colored area of flesh next to the skin is approximately 1.0 mm. Fibers in the flesh are conspicuous.

(24) The seed is approximately 4.1 cm in length and 3.8 cm in width in size. The seed has a generally triangular shape, in longitudinal section, and a generally circular shape in cross-section. The color of the seed coat, when fresh, is greyed-orange (RHS 165A).

(25) The Merensky 5 fruit ripened in February in Tzaneen, South Africa and in October in California, USA. The fruit of the Merensky 5 is not intended for market use, but rather the variety is used as a rootstock onto which commercial varieties such as Hass are grafted.

(26) As can be seen from the data in Table 5 below, the Merensky 5 rootstock having Hass scion yielded a greater cumulative yield in kilograms per tree than a Merensky 2 rootstock having the Hass scion.

(27) TABLE-US-00005 TABLE 5 Yield (kg/tree) Rootstock Year 2 Year 3 Year 4 Cumulative Merensky 5 7.22 13.72 58.01 78.95 Merensky 2 11.03 14.03 43.19 68.25 Tzaneen, Limpopo Province, South Africa, with Hass scion

(28) The Merensky 5 variety has shown a strong resistance and tolerance to Phytophthora cinnamomi. Moreover, Merensky 5 has shown to be tolerant to salinity.