Assessing Avocado for Laurel Wilt Resistance, Fruit Quality, and Horticultural Traits for Production in East Central Florida

Avocado (Persea americana Mill.) is a high-value specialty crop commercially grown in California and Florida. The avocado industry is newly threatened by the fungal laurel wilt (LW) pathogen (Raffaelea lauricola) vectored by an 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. A population of 'Hass' x 'Bacon' and 'Bacon' x 'Hass' was planted in Ft. Pierce, FL for a genetic mapping study. Extensive phenotypic data on tree growth, fruit quality (fruit weight, seed weight, fruit size and diameter, oil content, number of fruits per tree, fruit dry weight, fruit and pulp firmness, and peel color), and disease resistance is being collected over the next three years. Evaluation of bloom was conducted on a two-week interval until the occurrence of fruit set. Flowers were assessed on the presence of clusters and flowers per shoot with an estimation of open flowers at each evaluation. On trees that flowered, they occurred on almost every shoot apex with an average of 42% open flowers on 4 March 2013. By 26 April 2013, there were less than 5% open flowers on each cluster. Peak bloom ranged from 14 March to 26 April 2013. Edible and non-edible portions of the fruit were evaluated according to presence/absence of common disorders such as flesh bruising and other body rots. Other less common disorders such as vascular leaching, stones in the flesh, flesh adhesion to the seed, and uneven ripening were also noted.  Fruit weight was highly variable, ranging between 96.8 and 686.6 g. Lightest and heaviest seed weight ratios were 5.9 and 5.5 g. Range of flesh weight ratios were 2.7 to 10.2 g. An informal taste panel was conducted with 10 judges on seven selections using a store-bought Hass as the standard. 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 g and the skin turns dark during ripening helping mask minor imperfections. This extensive set of phenotypic data will be used to identify DNA markers associated with important traits.