New Germplasm Could Help Protect Avocados from Root Rot Disease

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Submitted by News on August 13, 2008 - 12:08pm.

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Avocado in a tree.
Genes are being sought to make Florida avocadosmore resistant to Phytophthora root rot, which could become more of aproblem as Everglades restoration projects raise the water table. Photocourtesy of Mark W. Skinner. USDA NRCS NPDC.


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New Germplasm Could Help Protect Avocados from Root RotDisease

By AlfredoFlores
August 1, 2008

New germplasm to broaden the geneticdiversity of avocados is being collected by Agricultural Research Service (ARS)scientists and cooperators to help protect this popular fruit from a fungusthat damages avocado tree roots.

To help combat Phytophthora root rot (PRR), researchers at the ARSNational GermplasmRepository in the Subtropical Horticultural Research Station in Miami arescreening the germplasm for markers for genes that might confer resistance toPRR.

The research is led by plant geneticistRaySchnell at the ARS Miami lab. Cooperators are molecular biologist JamesBorrone (now at Oklahoma StateUniversity), and colleagues at the Universityof Florida (UF).

The avocado, a staple in the Mexican diet, is also very popular among U.S.households—so much so that 43 percent buy avocados. The avocado tree,native to the area from Mexico to northern South America, produces a fruit thatis unique and nutritious. Avocados contain 60 percent more potassium thanbananas, and are also rich in B vitamins and vitamins E and K.

The researchers are searching for ways to make avocado (Perseaamericana) more resistant to PRR, which causes the roots of P.americana to rot and, if untreated, to die. Excess water predisposes theplants to PRR. This has not been a major problem in south Florida due to thelimestone soils and excellent drainage, but one of the major goals of theEverglades restoration project is to raise the water table to restore the waterflow in Everglades National Park. Thiswill also increase the water table in the adjacent agricultural lands whereavocados are grown, potentially increasing the occurrence of PRR.

Using genetic sequence information, genetic markers (called microsatellites)were developed. Genetic diversity in the collection of 224 accessions has beenstudied using the genetic markers and, based on this study, researchers plan toadd new avocado types from the West Indies.

These molecular genetic markers will be useful for characterizing germplasm,and for developing PRR-tolerant avocado rootstock.

Readmore about the research in the August 2008 issue of AgriculturalResearch magazine.

ARS is a scientific research agency of the U.S. Department of Agriculture.


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