USPP24258P3 - Avocado rootstock named ‘Zentmyer’ - Google Patents

Abstract

A new and distinct variety of Persea americana tree having a high tolerance under most conditions to Phytophthora cinnamomi when used as a rootstock. However, it is severely damaged by salt and is not recommended for locations where salt is a problem. This variety does not yield well under non-root rot conditions in comparison to similar varieties, making it desirable for replant situations where root rot infested soils are a problem.

Description

Latin name of the genus and species:

The avocado cultivar of this invention is botanically identified as Persea americana Mill.

Variety denomination:

The variety denomination is ‘Zentmyer’.

BACKGROUND OF THE INVENTION

Avocado root rot is the limiting factor for the growth of avocados throughout the world. Avocado root rot is caused by the fungus Phytophthora cinnamomi, which attacks and kills the feeder roots of avocado trees. The resultant lack of roots causes the tree to eventually die from water stress. There are a number of varieties of rootstocks that have some tolerance to the disease. These varieties included ‘Duke 7’ (unpatented), the most commonly planted tolerant rootstock in the world; and ‘Thomas’ (U.S. Plant Pat. No. 6,628), another root rot tolerant rootstock. However, even with these rootstocks, growers must still use a variety of methods, including mounding, mulching and the applications of chemical fungicides, to keep the tress from dying in many soils. More resistant rootstocks are necessary to eliminate avocado root rot as a major disease threat.

Screening and Greenhouse Evaluation of Rootstocks

‘Zentmyer’ was identified and characterized using the following screening protocol. As it is difficult to breed avocados because only one in approximately one thousand flowers actually set fruit, plant breeding blocks of avocados were isolated to prevent out crossing with susceptible rootstocks. The breeding blocks were made up of various combinations of selected rootstocks including, ‘Thomas’ (U.S. Plant Pat. No. 6,628), ‘Barr Duke’ (U.S. Plant Pat. No. 6,627), ‘G6’, ‘Duke 7’, ‘Duke 9’, ‘UC 2001’, ‘UC 2011’, ‘Toro Canyon’ (U.S. Plant Pat. No. 5,642), ‘Spencer’, ‘CR1-71’, ‘G 810’, ‘G 875’, ‘G 755A’, ‘VC 256’, and ‘Steyemarkii’. In order to synchronize blooming, attempts were made to girdle late-blooming varieties and spray early-blooming varieties with the pesticide Unicona-zole-P.

Initial screening was carried out by germinating seeds, which were harvested from the breeding blocks, in flats of vermiculite in the greenhouse. Phytophthora cinnamomi-infested millet was placed in rows along with the young roots of the test seedlings. After 8-10 weeks roots were evaluated and those with a high percentage of surviving roots were transplanted to soil mix incorporated with P. cinnamomi-infested millet. Rootstocks that survived this test were planted and grown in P. cinnamomi-infested soils. Survivors were examined more carefully for various types of resistance using asexual propagated material.

• • a. Root survival—Rootstocks were grown in typical California avocado soils, inoculated with P. cinnamomi and evaluated for growth, root length and percent healthy roots.
  • b. Root regeneration—Rootstocks were grown in soil inoculated with P. cinnamomi, treated with Aliette to halt Phytophthora root rot and evaluated for root regeneration.
  • c. Attraction to P. cinnamomi—Roots of the rootstocks were placed in water baths with motile zoospores of P. cinnamomi. The numbers of spores attracted to the roots were evaluated.

Rootstocks that performed well in the screening and greenhouse evaluations were further tested under field conditions.

Selection of ‘Zentmyer’

‘Zentmyer’ was developed at Riverside, Calif. The maternal parent is ‘Thomas’ (U.S. Plant Pat. No. 6,628) avocado variety. The pollen parent is unknown. Specifically, the ‘Zentmyer’ rootstock variety was selected in 1993 from an agricultural operations land located Riverside, Calif. The fruit were collected from the avocado breeding blocks, the seed removed, and planted in vermiculite. The seeds were grown in a greenhouse. The plants were inoculated with the fungus Phytophthora cinnamomi. After showing tolerance to the disease, ‘Zentmyer’ was selected as a single plant for further testing. Budwood was collected from the plants and grafted to the stumps of adult avocado trees that had been cut down at Irvine, Calif. The new varieties grew into trees which provided budwood for further testing. At least two ‘mother’ trees of the variety are growing in Irvine Calif., along with the germplasm. During screening and evaluation, ‘Zentmyer’, which was selected and originally designated ‘PP4’, distinguished itself from other varieties, including the maternal parent ‘Thomas,’ by having a high tolerance against Phytophthora root rot. The properties of ‘Zentmyer’ were found to be true to type and transmissible by asexual reproduction.

BRIEF SUMMARY OF THE INVENTION

This invention relates to a new and distinct avocado variety. ‘Zentmyer’ is an avocado tree having a rootstock that has a high tolerance against Phytophthora root rot under most conditions. However, it is severely damaged by salt and is not recommended for locations where salt is a problem. This variety also does not yield well under non-root rot conditions in comparison to similar varieties. For these reasons it may be an excellent choice for replant situations where root rot infested soils are a problem.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a nine-year-old top-worked tree of the ‘Zentmyer’ variety while growing in Irvine, Calif.

FIG. 2 illustrates typical mature foliage of the ‘Zentmyer’ variety with dimensions in centimeters shown at the right.

FIG. 3 illustrates typical flush foliage of the ‘Zentmyer’ variety with dimensions in centimeters shown at the bottom.

FIG. 4 a illustrates typical inflorescence with dimensions in centimeters shown at the right and FIG. 4 b illustrates typical inflorescence by itself.

FIG. 5 illustrates a typical external view of the fruit of the ‘Zentmyer’ variety, with dimensions in centimeters shown at the bottom.

FIG. 6 illustrates typical internal views of the fruit of the ‘Zentmyer’ variety, with and without the seed. Dimensions in centimeters are shown at the bottom.

DETAILED DESCRIPTION OF THE INVENTION

The following is a detailed description of the new ‘Zentmyer’ variety, which was taken from an approximately nine-year-old mature tree, with the exception as a rootstock for a specific scion when reference is made to root rot resistance and salinity tolerance. The tree is located in an experimental orchard in Irvine, Calif. and is grafted on a Persea americana seedling used as a rootstock.

The Royal Horticultural Society (R.H.S.) Color Chart is used herein for the color description of the rind, seed, bark, leaf, flower, flesh color and other interest of the ‘Zentmyer’ avocado tree.

Trees, Foliage, and Flowers

• Tree:
  • • Growth habit.—Vigorous, upright and spreading when compared to the rootstock ‘Thomas’.
    • Vigor.—Below are data on the vigor of ‘Hass’ grafted onto the rootstock of ‘Zentmyer’, as determined by trunk diameter measurements from trees planted in an orchard with Phytophthora cinnamomi in Escondido Calif.

TABLE 1
Trunk diameter (cm)

	Rootstock	year 1	year 2	year 3	year 4	year 5
	PP#4 ‘Zentmyer’	2.40	4.39	7.12	9.20	11.25
	Thomas	2.44	4.29	6.75	8.40	10.84
	Escondido Ca., with Hass scion

TABLE 2
Canopy volume (cubic feet)

	Rootstock	year 1	year 2	year 3	year 4	year 5
	PP#4 ‘Zentmyer’	14.81	77.27	397.4	410.	1573
	Thomas	13.56	84.48	388.5	367.	1076
	Escondido Ca., with Hass scion

• • • Size.—Medium. The typical canopy size of a three year old top-worked ‘Thomas’ is 388 cu.ft. By comparison the canopy size of a three year old top-worked ‘Zentmyer’ is 397 cu.ft. The tree is 610-915 cm in height when fully grown at the orchard site in Irvine, Calif.
• Branch:
  • • Color.—The color of the one year old branch is green (RHS 144D).
    • Smoothness.—The bark of a one year old branch is smooth.
    • Lenticels.—The lenticels of a one year old branch are conspicuous.
• Main stem:
  • • Color.—Grayed-green (RHS 197A and RHS 197D).
    • Texture of bark.—Corky.
• Young shoot (flush):
  • • Intensity of anthocyanin coloration.—Weak.
    • Anthocyanin coloration.—Grayed-orange (RHS 166A).
    • Color.—Grayed-orange (RHS 166A).
    • Conspicuousness of lenticels.—Medium.
    • Color of lenticels.—Purple (RHS 185B).
    • Size of lenticels.—1.0 mm long.
    • Concentration of lenticels.—+/−26 lenticels per square cm.
    • Color of upper side.—Grayed-orange (RHS 174A).
    • Glossiness of upper side.—Medium.
    • Color of lower surface.—Grayed-orange (RHS 177A).
• Mature leaf:
  • • Length.—15.0 cm.
    • Width.—6.0 cm.
    • Ratio length/width.—2.5.
    • Shape.—Lanceolate.
    • Color of upper side.—Green (RHS 137A).
    • Color of lower side.—Green (RHS 138B).
    • Glossiness of upper side.—Medium.
    • Prominence of veins on lower side.—Prominent and in relief.
    • Color of veins.—Yellow-green (RHS 151A).
    • General shape and cross-section.—Concave.
    • Reflexing of apex.—Absent.
    • Color of petiole.—Yellow-green (RHS 144A).
    • Anise aroma.—Absent.
    • Margin.—Undulation of margin is absent or very weak, and the leaf margin is entire.
    • Leaf apex shape.—Acuminate.
    • Leaf base shape.—Lanceolate.
    • Length of leaf petiole.—Approximately 3.0 cm.
    • Diameter of leaf petiole.—Approximately 3.5 mm.
    • Leaf arrangement.—Upright.
• Flower:
  • • Bud size.—Approximately 5 mm in length and approximately 4 mm in diameter.
    • Bud shape.—Ovoid.
    • Bud color.—Yellow-green (RHS 153A).
    • Opening.—Belongs to group “A”, male opening (i.e. with mature stamens) occurs in the afternoon, the flower closes over night, and female opening (i.e. with mature pistil) occurs the next morning; the flower's opening cycle lasts 20-24 hours.
    • Petals.—Borne in two whorls of three perianth lobes. The petals possess entire margins and petal coloration is near yellow-green (RHS N144B). Both the upper and lower petal surfaces are near yellow-green (RHS N144B).
    • Stamen.—There are commonly nine fertile stamens with each having two basal nectar glands that are greyed-oranged (RHS 174A) in color and three staminodia. The anthers are tetrathecal.
    • Pistil.—The single pistil with a slender style and small stigmatic surface has one carpel with one ovule. The ovary is superior.
    • Sepals.—There are 6 sepals which are approximately 7 mm in length and approximately 4 mm in width, and the color of both sepal surfaces is yellow-green (RHS 151A).
    • Pedicel.—Commonly approximately 7 mm in length and approximately 1.9 mm in diameter. The coloration is near yellow-green (RHS N144A).
    • Peduncles.—Approximately 2.0 cm in length and approximately 5.0 mm in diameter. The coloration is yellow-green (RHS 151A).
    • Number of flowers on inflorescence.—Approximately 170-200 flowers per inflorescence.
    • Fragrance.—Absent.
    • Bloom.—Bloom period at Riverside, Calif. experiment station varies with cultural conditions. On average ‘Zentmyer’ has been found to bloom from 1st of February through 20th of March.
      Fruit, Fruit and Production Characteristics
• Fruit:
  • • Length.—9.5 cm.
    • Width.—5.5 cm.
    • Ratio length/width.—1.7.
    • Weight.—146.1 grams.
    • Shape.—Obovate, with an apex and base diameter of approximately 3.5 cm and a center diameter of approximately 5.5 cm.
    • Color of skin (when ripe).—Yellow-green (RHS 144A) with some patches of purple (RHS N79).
    • Texture of skin.—Smooth.
    • Presence of longitudinal ridges.—Absent.
    • Thickness of skin.—Thin.
    • Adherence of skin to flesh.—Strong.
    • Main color of flesh.—Yellow-green (RHS 154C).
    • Color of intensely colored area of flesh next to skin.—Green (RHS 140A).
    • Width of intensely colored area next to skin.—3.0 mm.
    • Conspicuousness of fibers in flesh.—Inconspicuous.
• Seed:
  • • Length.—5.6 cm.
    • Width.—3.4 cm.
    • Weight.—20.8 grams.
    • Shape (in longitudinal section).—Elliptical.
    • Shape (in cross section).—Circular.
    • Color of seed coat (fresh).—Grayed-orange (RHS 166B).
    • Cotyledon color.—Orange-white (RHS 159B).
    • Time of harvesting.—‘Zentmyer’ fruit ripen in September (in Riverside Calif.).
    • Resistance to pests.—Strong resistance to Phytophthora cinnamomi.
    • Tolerance to salinity.—Sensitive to salinity.
    • Market use.—The fruit of ‘Zentmyer’ are not intended for market use, but rather the variety is used as a rootstock onto which commercial varieties, such as ‘Hass’ are grafted.

TABLE 3
Rootstock rating at Santana, Ventura County, August 20011

	Tree rating	Canopy	Trunk	No. trees
Rootstock	(0-5; 5 = dead)	volume (cu ft)	diameter (cm)	dead
‘Steddom’	0.80 a	13.89 a	1.92 a	1
‘Merensky II’	0.90 a	15.10 a	1.48 a	1
‘Uzi’	0.90 a	16.92 a	2.02 a	0
‘Zentmyer’	1.05 a	16.48 a	2.05 a	1
‘G755A	1.65 a	5.55 a	1.62 a	1
(Brokaw)’
‘Medina’	1.90 a	12.66 a	1.70 a	2
‘Berg’	2.20 a	13.80 a	1.29 a	4
‘McKee’	2.35 a	9.05 a	1.52 a	1
‘Duke 7’	2.50 a	11.40 a	1.24 a	4
‘Thomas’	2.65 a	10.22 a	1.15 a	4
‘G755 A	2.75 a	11.66 a	1.49 a	2
(C&M)’
‘UC 2023’	3.00 a	6.21 a	1.25 a	3
1Mean values in each column followed by identical letters are not statistically different according to Waller's k-ratio t test.

TABLE 4
Rootstock rating at Santana, Ventura County, November 2002.
Two-year trial to-date.

	Tree rating	Canopy	Trunk	Fruit rating
	(0-5;	volume	diameter	(0-5;
Rootstock	5 = dead)	(cu ft)	(cm)	5 = heavy)

‘Merensky	0.17	d	72.27	abc	3.49	ab	0.78	bcd
II’
‘Uzi’	0.50	cd	69.64	abcd	3.64	a	2.50	a
‘Steddom’	1.00	bcd	67.95	abcd	2.94	abc	1.70	abc
‘Medina’	1.06	bcd	79.89	ab	3.26	ab	0.00	d
‘Zentmyer’	1.50	bcd	81.44	a	3.19	ab	0.60	bcd
‘Duke 7’	1.67	bcd	32.48	abcde	2.31	abcd	1.11	abcd
‘Berg’	1.72	bcd	46.57	abcde	2.21	abcd	2.00	ab
‘McKee’	1.78	abcd	30.92	bcde	2.24	abcd	0.22	cd
‘G755A	2.30	abcd	19.98	de	1.90	bcd	0.10	d
(Brokaw)’
‘Thomas’	2.60	abc	31.50	bcde	2.02	abcd	0.30	cd
‘UC 2023’	2.95	ab	25.50	cde	1.41	cd	0.20	d
‘G755A	4.00	a	15.71	e	0.82	d	0.00	d.
(C&M)’

		Tip burn	Canker	No. trees
	Rootstock	rating (0-5)	rating (0-5)	dead
	‘Merensky II’	0.00 a	0.33 a	0/9
	‘Uzi’	0.33 a	0.00 a	1/10
	‘Steddom’	0.25 a	0.00 a	2/10
	‘Medina’	0.75 a	0.00 a	1/9
	‘Zentmyer’	0.38 a	0.63 a	1/10
	‘Duke 7’	0.38 a	0.38 a	3/9
	‘Berg’	0.17 a	0.83 a	3/9
	‘McKee’	0.43 a	0.29 a	2/10
	‘G755A (Brokaw)’	0.29 a	0.14 a	3/10
	‘Thomas’	0.17 a	1.00 a	4/10
	‘UC 2023’	0.00 a	0.00 a	5/10
	‘G755A (C&M)’	—	—	8/10

TABLE 5
{Leo Curillo) rootstock rating, December 2003.
Three-year trial to-date.

	Tree rating	Canopy	Trunk
	(0-5;	vol	diam	Fruit rating
Rootstocks	5 = dead)	(cu ft)	(cm)	(0-5; 5-heavy)
‘Zentmyer’	0.313d	48.0ab	6.45a	1.75abc
‘Merensky’	0.556cd	71.6a	6.49a	2.67a
‘Steddom’	0.677bcd	47.2ab	5.18ab	2.00ab
‘Parida’	1.147abcd	50.6ab	4.91ab	1.53abcd
‘Evstro’	1.353abcd	49.6ab	5.55ab	2.29ab
‘Merensky I’	1.441abcd	48.6ab	5.01ab	1.41bcd
‘Guillemet’	1.588abc	39.6b	4.58b	0.41d
‘Thomas’	1.875ab	43.4ab	4.45b	0.72cd
‘UC 2023’	2.188a	27.2b	4.07b	0.31d
‘VC 207’	2.382a	32.4b	3.79b	1.12bcd

		Salt rating	Canker	No.
		(0-5;	rating	trees dead
	Rootstocks	5 = severe)	(0-5; 5-severe)	(%)
	‘Zentmyer’	0.00a	0.00a	0
	‘Merensky’	0.00a	0.00a	0
	‘Steddom’	0.00a	0.06a	6
	‘Parida’	0.00a	0.07a	18
	‘Evstro’	0.00a	0.06a	0
	‘Merensky I’	0.00a	0.06a	18
	‘Guillemet’	0.00a	0.08a	22
	‘Thomas’	0.00a	0.08a	29
	‘UC 2023’	0.08a	0.00a	19
	‘VC 207’	0.00a	0.00a	35
Mean values in each column followed by identical letters are not statistically different according to Waller's k-ratio t test.

TABLE 6
Rootstock ratings of avocado trees planted in root rot soil at
Escondido, July 2002

	Tree	Canopy	Trunk	Fruit set
	rating	volume	diameter	rating 0-5;
Rootstocks	0-5; 5 = dead	Cu ft	Cm	5 = heavy
‘Zentmyer’	0.00c	397.4abc	7.12bcd	1.53cd
‘Rio Frio’	0.00c	313.5cdef	6.33cdef	2.13bcd
‘Merens I’	0.00c	543.6a	8.74a	3.50a
‘Merensk II’	0.02c	409.0abc	7.81abc	2.84ab
‘VC 241’	0.06c	238.4defg	6.19defg	1.41cd
‘Uzi’	0.29bc	504.3ab	8.57ab	2.76ab
‘Steddom’	0.36bc	376.1bcde	7.07bcd	2.43bc
‘Thomas’	0.44bc	388.5bcd	6.75cde	1.12de
‘Guillemet’	0.59bc	192.0fgh	4.90fgh	1.12de
‘Spencer sdlg’	0.63bc	225.8efg	5.24efgh	1.56cd
‘Leo’	0.67bc	288.2cdef	5.89defgh	1.60cd
‘Spencer clonal’	0.69bc	163.8fgh	4.65gh	1.54cd
‘Duke 7’	1.00b	129.3gh	4.38h	1.47cd
‘G755A’	0.16b	294.1cdef	5.86defgh	1.56cd
‘PolyN’	4.12a	65.6h	1.26i	0.24e

Tip Burn

Cankers

Dead

	Rootstocks	Number trees affected

	‘Zentmyer’	0	0	0/15
	‘Rio Frio’	0	0	0/16
	‘Merens I’	0	0	0/14
	‘Merensk II’	0	1	0/17
	‘VC 241’	0	0	0/16
	‘Uzi’	2	0	1/17
	‘Steddom’	0	0	1/14
	‘Thomas’	0	0	1/17
	‘Guillemet’	3	1	2/17
	‘Spencer sdlg’	0	0	2/16
	‘Leo’	0	0	2/15
	‘Spencer clonal’	0	0	5/16
	‘Duke 7’	0	0	3/15
	‘G755A’	2	1	3/16
	‘PolyN’	0	0	14/17

TABLE 7
rootstock trial tree ratio April 20031. Four-year trial to-date

	Tree rating	Canopy	Trunk
Rootstock	(0-5; 5 = dead)	volume (cu ft)	diam. (cm)	Salt
‘MerenI’	0.00d	551ab	10.7a	0.08cd
‘VC241’	0.06d	281efgh	8.0abc	0.03cd
‘Rio Frio’	0.07d	362efcd	8.7abc	0.00d
‘Zentmyer’	0.07d	410bcde	9.2ab	0.32bc
‘MerenII’	0.18d	532abc	9.4ab	0.21dc
‘Spen sdlg’	0.36d	263efgh	6.9bc	0.00d
‘Uzi’	0.38d	669a	10.6a	0.68a
‘Steddom’	0.39d	478bcd	8.6abc	0.32bc
‘Thomas’	0.47cd	367cdef	8.4abc	0.62ab
‘Leo’	0.77cbd	274efgh	7.3abc	0.13cd
‘Guillemet’	0.83cbd	190ghi	6.2bc	0.13cd
‘Duke7’	1.34cb	127hi	8.8abc	0.16cd
‘Spen cl’	1.44b	211fghi	5.3c	0.12cd
‘G755A’	1.69b	322defg	7.0bc	0.25cd
‘PolyN’	4.15a	77i	1.5d	0.06cd

		Canker	Fruit	Dead trees
	Rootstock	(0-5; 5 = heavy)	rating2	(%)
	‘MerenI’	0a	2.97abc	0
	‘VC241’	0a	3.41ab	0
	‘Rio Frio’	0a	3.73a	0
	‘Zentmyer’	0a	3.71a	0
	‘MerenII’	0.1a	2.97abc	0
	‘Spen sdlg’	0a	3.57ab	7
	‘Uzi’	0a	3.47ab	6
	‘Steddom’	0a	3.75a	7
	‘Thomas’	0a	3.53ab	6
	‘Leo’	0a	3.29ab	13
	‘Guillemet’	0a	2.90abc	13
	‘Duke7’	0a	1.53de	19
	‘Spen cl’	0a	2.35bcd	23
	‘G755A’	0a	1.78cd	25
	‘PolyN’	0a	0.29e	82
1Mean values in each column followed by identical letters are not statistically different according to Waller's k-ratio t test.
2Fruit was rated in November 2003.

TABLE 8
Temecula, yield 20031;2. Four year trial to-date.

	Fruit weight/tree	Number	Fruit weight
Rootstock	(kg)	fruit/tree	(kg)

‘Zentmyer’	15.89a	68.64a	0.219a
‘Uzi’	13.99ab	59.24ab	0.195ab
‘Spencer	12.52ab	56.27ab	0.181ab
seedling’
‘Merensky II’	11.83ab	51.12ab	0.185ab
‘Rio Frio’	10.87abc	51.33ab	0.187ab
‘Steddom’	10.01abc	46.20abc	0.175abc
‘Thomas’	8.50abcd	40.12abcd	0.154abc
‘G755A’	8.08abcd	34.56abcd	0.116bc
‘VC241’	7.44bcd	31.75bcd	0.202ab
‘Guillemet’	7.42bcd	30.00bcd	0.196ab
‘Spencer clonal’	6.99bcd	32.00bcd	0.136abc
‘Merensky I’	6.95bcd	32.08bcd	0.148abc
‘Leo’	6.53bcd	28.14bcd	0.140abc
‘Duke 7’	3.33cd	14.81cd	0.138abc
‘PolyN’	1.72d	5.71d	0.076c
1Mean values in each column followed by identical letters are not statistically different according to Waller's k-ratio t test.
2Only fruit which were grade size were picked; remaining fruit on trees to be picked later.

TABLE 9
Escondido, Tree ratings, July 2002

	Tree rating	Canopy	Trunk diam
Rootstock	(0-5; 5 = dead)	vol. (cu ft)	(cm)

‘Uzi’	0.039	b	34.69	a	2.43	a
‘Guillemet’	0.042	b	22.86	a	2.06	a
‘Zentmyer’	0.077	b	22.40	a	2.25	a
‘Spencer sdlg’	0.536	b	27.81	a	2.01	a
‘Steddom’	0.615	b	18.93	a	1.99	a
‘Berg’	0.714	b	21.42	a	1.98	a
‘Merensky II’	0.750	b	32.07	a	2.10	a
‘Elinor’	0.786	b	29.44	a	2.03	a
‘Thomas’	0.846	b	23.07	a	1.85	a
‘Pond’	1.00	ab	30.55	a	2.15	a
‘Crowley’	1.083	ab	23.78	a	1.86	a
‘G755A’	1.231	ab	22.64	a	1.85	a
‘Duke 9’	2.270	a	9.40	a	1.07	b

	No. trees	No. trees	No. trees
Rootstock	Dead	w/ tip burn	w/ canker
‘Uzi’	0	6	0
‘Guillemet’	0	4	0
‘Zentmyer’	0	2	0
‘Spencer sdlg’	0	2	1
‘Steddom’	1	0	0
‘Berg’	0	1	2
‘Merensky II’	2	0	1
‘Elinor’	1	0	2
‘Thomas’	1	2	0
‘Pond’	1	0	2
‘Crowley’	2	1	0
‘G755A’	2	0	0
‘Duke 9’	5	0	0
There were significant differences at P = 0.01 between blocks for all tree parameters analyzed.

TABLE 10
Tree ratings, April 2003. Two-year trial to-date.

	Tree rating	Canopy	Trunk	Fruit rating
	(0-5;	vol	diam	(0-5;
Rootstock	5 = dead)	(cu ft)	(cm)	5 = heavy)

‘Uzi’	0.267	c	88.76 a	4.193	a	0.0 a
‘Berg’	0.531	c	44.16 a	2.956	bc	0.0 a
‘Zentmyer’	0.600	c	54.37 a	3.393	ab	0.0 a
‘Merensky	0.833	bc	68.49 a	3.333	ab	0.0 a
II’
‘Steddom’	0.867	bc	56.42 a	3.127	ab	0.0 a
‘Pond’	0.906	bc	55.05 a	3.188	ab	0.0 a
‘Spenser	0.906	bc	51.45 a	2.988	bc	0.0 a
sdlg’
‘Crowley’	0.964	bc	42.05 a	3.021	bc	0.0 a
‘Thomas’	1.071	bc	49.99 a	2.900	bc	0.0 a
‘Guillemet’	0.167	abc	43.64 a	2.960	bc	0.1 a
‘Elinor’	1.393	abc	58.40 a	2.864	bc	0.0 a
‘G755A’	2.156	ab	44.21 a	2.819	bc	0.0 a
‘Duke 9’	2.577	a	32.16 a	1.885	c	0.0 a

	Salt rating	Canker rating	No. trees
Rootstock	(0-5; 5 = severe)	(0-5; 5 = severe)	Dead (%)

‘Uzi’	0.933	ab	0.000 a	0
‘Berg’	0.633	abcd	0.000 a	6
‘Zentmyer’	1.000	a	0.000 a	7
‘Merensky II’	0.154	cd	0.308 a	13
‘Steddom’	0.321	bcd	0.286 a	7
‘Pond’	0.767	abc	0.200 a	6
‘Spenser sdlg’	0.300	bcd	0.200 a	6
‘Crowley’	0.083	d	0.000 a	14
‘Thomas’	0.731	abc	0.000 a	0
‘Guillemet’	0.615	abcd	0.133 a	13
‘Elinor’	0.333	bcd	0.167 a	14
‘G755A’	0.846	ab	0.077 a	13
‘Duke 9’	0.313	bcd	0.500 a	38

TABLE 11
Santa Paula, rootstock rating, December 2002

	Tree rating	Canopy	Trunk
Rootstock	(0-5; 5 = dead)	vol (cu ft)	diam (cm)	Fruit set

‘McKee’	0.00 b	51.41 a	3.45	bc	0.00 a
‘Merensky II’	0.00 b	53.45 a	3.66	ab	0.00 a
‘Pond’	0.00 b	55.08 a	3.69	a	0.00 a
‘Guillemet’	0.00 b	37.98 b	2.71	f	0.00 a
‘Zentmyer’	0.00 b	51.92 a	3.38	cd	0.00 a
‘Thomas’	0.00 b	36.66 b	3.15	de	0.00 a
‘Crowley’	0.03 b	34.91 b	3.17	d	0.05 a
‘Duke 9’	0.05 b	31.93 b	2.93	ef	0.00 a
‘Steddom’	0.27 a	37.14 b	2.75	f	0.00 a

		Salt burn		Trees
	Rootstock	(0-5; 5-heavy)	Cankers	dead (%)
	‘McKee’	0	0	0
	‘Merensky II’	0	0	0
	‘Pond’	0	0	0
	‘Guillemet’	0	0	0
	‘Zentmyer’	0	0	0
	‘Thomas’	0	0	0
	‘Crowley’	0	0	0
	‘Duke 9’	0	0	0
	‘Steddom’	0	0	0
Mean values in each column followed by identical letters are not statistically different according to Waller's k-ratio.

TABLE 12
Santa Paula, rootstock rating, December 2003. Two-year trial to-date.

	Tree rating	Canopy	Trunk	Fruit
Rootstock	(0-5; 5 = dead)	vol (cu ft)	diam (cm)	set
‘McKee’	0.025b	184.1b	5.88bc	1.90ab
‘Merensky II’	0.000b	246.8a	6.18abc	2.60a
‘Pond’	0.000b	192.0b	6.24ab	0.00d
‘Guillemet’	0.000b	118.8cd	5.38de	0.00d
‘Zentmyer’	0.026b	182.8b	6.41a	1.32bc
‘Thomas’	0.237a	174.9b	5.72cd	0.47cd
‘Crowley’	0.150ab	124.7c	5.42de	2.15ab
‘Duke 9’	0.053ab	132.6c	5.19e	1.89ab
‘Steddom’	0.083ab	86.3d	5.00e	2.00ab

		Salt burn		Trees
	Rootstock	(0-5; 5-heavy)	Cankers	dead (%)
	‘McKee’	0	0	0
	‘Merensky II’	0	0	0
	‘Pond’	0	0	0
	‘Guillemet’	0	0	0
	‘Zentmyer’	0	0	0
	‘Thomas’	0	0	0
	‘Crowley’	0	0	0
	‘Duke 9’	0	0	0
	‘Steddom’	0	0	0
Mean values in each column followed by identical letters are not statistically different according to Waller's k-ratio t test..

TABLE 13
Temecula rootstock ratings, Sept 2002

	Tree rating			Fruit rating
	(0-5;	Canopy	Trunk	(0-5;
Rootstock	5 = dead)	vol (cu ft)	diam (cm)	5 = heavy)

‘Zentmyer’	0.400	c	40.70	ab	2.79	a	0.00 b
‘Crowley’	0.618	c	40.38	ab	2.86	a	0.00 b
‘Elinor’	0.824	c	40.52	ab	2.54	a	0.00 b
‘Guillemet’	0.882	bc	39.13	ab	2.42	a	0.00 b
‘Steddom’	0.969	bc	29.20	bc	2.13	ab	1.16 a
‘Thomas’	0.969	bc	31.46	bc	2.13	ab	0.00 b
‘Pond’	1.088	bc	54.08	a	2.78	a	0.00 b
‘Uzi’	1.188	bc	35.08	ab	2.56	a	0.00 b
‘G755A’	2.088	ab	37.85	ab	2.41	a	0.00 b
‘Spencer	2.906	a	11.96	c	1.39	b	0.00 b
sdlg’

				No.
		Salt damage	Cankers	trees
	Rootstock	(0-5; 5 = heavy)	(0-5; 5 = heavy)	dead

	‘Zentmyer’	1.50	ab	0.00 a	0/15
	‘Crowley’	1.34	b	0.00 a	1/17
	‘Elinor’	1.59	ab	0.00 a	1/17
	‘Guillemet’	1.41	b	0.00 a	2/17
	‘Steddom’	1.54	ab	0.50 a	2/16
	‘Thomas’	1.50	ab	0.00 a	3/16
	‘Pond’	1.40	b	0.00 a	2/17
	‘Uzi’	1.64	ab	0.00 a	2/16
	‘G755A’	2.50	ab	0.36 a	4/17
	‘Spencer sdlg’	2.63	a	0.00 a	4/16

TABLE 14
Temecula, rootstock ratings, December 2003. Two-year trial to-date.

	Tree rating			Fruit rating
	(0-5;	Canopy	Trunk	(0-5;
Rootstock	5 = dead)	vol (cu ft)	diam (cm)	5 = heavy)
‘Zentmyer’	0.313c	207.27a	6.23a	2.063a
‘Pond’	0.906c	307.04a	5.75a	1.813a
‘Elinor’	0.912c	170.37a	4.80a.	1.059a
‘Guillemet’	1.059c	199.37a	5.73a	0.882a
‘Uzi’	1.094bc	206.04a	4.35a	0.813a
‘Crowley’	1.250bc	144.14a	5.04a	1.438a
‘Steddom’	1.281bc	254.94a	4.89a	1.188a
‘Thomas’	1.313be	226.39a	5.16a	1.375a
‘G755A’	2.438ab	175.55a	5.23a	0.625a
‘Spencer	2.813a	42.12a	2.26a	0.519a
sdlg’

		Salt damage	Cankers	Trees
	Rootstock	(0-5; 5 = heavy)	(0-5; 5 = heavy)	dead (%)
	‘Zentmyer’	1.188ab	0.000a	0
	‘Pond’	0.321cd	0.000a	13
	‘Elinor’	0.469cd	0.000a	6
	‘Guillemet’	0.893abc	0.000a	18
	‘Uzi’	0.769abcd	0.000a	19
	‘Crowley’	0.731abcd	0.000a	19
	‘Steddom’	0.167d	0.000a	25
	‘Thomas’	1.308a	0.000a	19
	‘G755A’	1.167ab	0.000a	25
	‘Spencer sdlg’	0.500bcd	0.000a	44

Claims (1)

What is claimed is:

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

Images