1. Assessing Avocado for Laurel Wilt Resistance, Fruit Quality, and Horticultural Traits for Production in East-Central Florida Cristina Pisani1, Mark A. Ritenour1, Ed Stover2, Anne Plotto2, Randy C. Ploetz3, Osman A. Gutierrez4, and David Kuhn4 1Indian River Research and Education Center, Univ. of FL, Ft. Pierce, FL USDA-ARS, U.S. Horticultural Research Laboratory, Ft. Pierce, FL Department of Plant Pathology, Univ. of Florida, Homestead, FL USDA-ARS, Subtropical Horticulture Research Station, Miami, FL 33158
INTRODUCTION
Avocado (Persea americana Mill.) is a high-value specialty crop with U.S. commercial production in California and Florida. The Florida avocado industry contributes ~$13 million to the economy with ~6,800 production acres in Miami Dade County. Unfortunately, the avocado industry is threatened by the fungal disease laurel wilt (LW; Raffaelea lauricola) vectored by the Asian ambrosia beetle Xyleborus glabratus. Identification of an LW-resistant cultivar with good fruit quality and horticultural traits may provide a useful alternative crop in east-central Florida where citrus production is markedly declining.
GENERAL OBJECTIVES
Phenotypic data collection on a California population of Hass x Bacon & Bacon x Hass for a genetic mapping study
Identify selections for East-Central Florida with excellent horticultural traits and disease resistance
MATERIALS AND METHODS
Hass x Bacon and Bacon x Hass avocado
Bi-weekly bloom evaluation based on the
presence of clusters and flowers/shoot with an
estimation of open flowers at each evaluation
Two harvests took place on separate sets of trees loosely based on slowing of fruit sizing and beginning of fruit drop
16 fruits per tree were harvested for postharvest evaluation
Evaluation of fruit disorders, fresh and dry weight, size, skin color, seed weight, oil content, no. fruits/tree, and fruit and pulp firmness
Informal taste panel comprised of 10 judges with 6 promising selections plus store-bought Hass used as a control
Plant ID
Mean fruit length (mm)
Mean fruit width (mm)
Mean fruit weight (g)
Mean fruit flesh weight (g)
No. of fruit per tree
R5 T56
141.9
79.6
400.9
356.7 55
R6 T29
106.4
71.1
268.3
203.7
102
R7 T21
101.1
72.9
264.1
209.0
133
R7 T36
132.7
73.1
306.8
268.6
117
R8 T23
99.8
65.9
213.3
147.7 66
R8 T36
100.2
69.3
248.4
189.5
225
Date of harvest
No. of trees
Distance (mm)
Peak force (g)
Mean force (g)
10/29/2013
120
2.5
97.7
45.7
11/14/2013 44
81.9
38.6
Significance -
<.0001
Table 3: Tree differences in fruit in peak and mean force for first harvest and second harvest. Force was recorded at 2.5 mm deformation & determined at 2 points on the equatorial region of each fruit
Fig. 3: R5 T56 fruit selection of Bacon x Hass
Table 1: Mean fruit length, width, weight, flesh weight, and number of fruits per tree from six promising avocado selections
Plant ID
Days to reach ripeness stage
Whole fruit firmness (N)
R5 T56 12
18.7
R6 T29 11
20.6
R7 T21
16.5
R7 T36
16.2
R8 T23 13
20.0
R8 T36
14.7
Photo courtesy of D. Kuhn
Table 2: Whole fruit firmness of first year selections of Hass x Bacon and Bacon x Hass avocado. Fruit were considered ripe upon reaching 10 to 20 N
Fig. 4: Panelists overall liking of first year selections based on % responses for texture and flavor
Fig. 2: Avocado flowers opened in the female stage
CONCLUSIONS & DISCUSSION
Peak bloom ranged from March 14 to April
Flowers occurred on almost every shoot apex with 40% open flowers on March 4, 2013
Less than 5% of open flowers remained by April 26, 2013
Mean fruit weight was highly variable between individual hybrids, ranging between 96.8 and grams & range of seed/flesh weight was 2.7 to 10.4
In a taste panel, there was no statistical difference in preference among Hass and initial hybrid selections. Numerically, R8 T36 selection was liked just as much as the store-bought Hass. One of the selections that panelists “liked moderately” and “liked very much” was rated as having a creamy and smooth texture with a nutty flavor. This selection is promising as it has a seed to flesh weight ratio of 8.1 and the skin turns dark during ripening helping mask minor imperfections
We have a population with good variability & a lot of diversity that we were able to identify
Extensive phenotypic dataset will be used to identify DNA markers with important traits of interest
Fig. 1: Date of peak bloom from 3/4/23 to 4/26/13
ACKNOWLEDGEMENTS
We thank the University of Florida and United States Department of Agriculture for financial support. We also thank Shamima Hossain, Mac Hossain, Dave Wood, and USDA Ft. Pierce & Miami field crews for all laboratory & field assistance.
Fig. 5: First year avocado selections included in taste panel of Hass x Bacon & Bacon x Hass