Research Library

A grower’s profit margin is the difference between the input costs to produce a marketable crop and the gross amount of money realized from the sale of the “output”, or the production itself. Anything that affects one or both of these can make the difference between profit and loss. The management of the avocado tree under southern California conditions, which can experience rapid changes in temperature and relative humidity, provides a challenge under the best of conditions.

SSR technology is a powerful tool to determine the pollen parents of avocado progeny of known maternal genetic background. The four SSR markers we have selected for use to determine pollen parents are powerfully informative for the range of cross pollinizing cultivars available in the selected orchards and, therefore, highly capable of discerning the specific pollen parent of each sampled fruit. The cultivars included in the study are Bacon, Ettinger, Fuerte, Harvest, Hass, Lamb Hass, Marvel, Nobel, SirPrize and Zutano.

Ultimately, the control of Phytophthora root rot (PRR) of avocado will be accomplished with resistant rootstocks. Our goal is to find rootstocks that will eliminate Phytophthora cinnamomi as a serious pathogen on avocado. Our ability to find such rootstocks has been enhanced as a result of our breeding blocks where we focus on crossing already resistant rootstocks. Our objectives over the life of this project have been to collect, select, breed and develop avocado germplasm that exhibits resistance to Phytophthora root rot of avocado.

This 3-year project, funded jointly by the UC Discovery Program and the CAC, is approaching the end of its final year. It was designed to identify genetic markers that track the nutritional composition of avocado fruit (“nutritional phenotypes”) for implementation via marker-assisted selection. The discovery of candidate genes and development of SNP (Single Nucleotide Polymorphism) markers is complete, though additional markers are expected from

Traditional breeding approaches are used for the development of new avocado cultivars. In these approaches, fruit/seed are selected from cultivars with favorable

The original objective was to determine the impact of temperature on floral behavior and pollen tube growth and humidity on the proportions of self-, close, and cross-pollinated avocado fruit on trees growing in humid, coastal and dry, inland CA climates. Because self-pollination was demonstrated to be the prevailing mode of pollination in Florida cultivars in warm humid conditions, it was appropriate to determine if similar rates of self-pollination occur in a dry Mediterranean climate present in California.

The goal of the avocado scion breeding program is to help maintain and enhance the California avocado industry by introducing consistently heavier producing, high-quality avocado varieties, better pollinizer varieties, and to test improved rootstock hybrids. This is achieved through identification of material which is less prone to alternate bearing and more tolerant to adverse environmental conditions. Additionally identifying varieties with a more upright tree structure will assist in high density tree management schemes.

Since 2010 there has been an on-going process of critical review and change to production research funded by the California Avocado Commission (CAC). A number of changes to the system and process of production research have occurred that has set strategic goals and addressed weaknesses in the system. The most notable changes have been to improve the accountability of the research contracts and to place the research efforts in a multi-year context with well-defined objectives and milestones to be met as the research projects are conducted.

The results of this research will provide a valuable framework for cultural management decisions and future research on the physiology of the avocado. A more complete understanding of the tree’s response to environmental stresses will be a direct outcome of this research. The results of this research will validate the high temperature sensitivity of ‘Hass’ and will explain why this variety is not necessarily well adapted in warm inland valleys.

Avocado breeding is challenged by the inability to perform controlled pollination, the long juvenility period of the trees (4–7 years) and their considerable size. Because of these difficulties, varietal improvement has long relied on multi-year field trials during which large numbers of seedlings are grown to maturity and screened for desirable (phenotypic) characteristics. Inferior trees are culled as their deficiencies become apparent, leaving only the most promising genotypes.