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["Lon J. Rombough" <lonrom@hevanet.com>]

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From: ARS News Service <NewsService@ars.usda.gov>
Reply-To: ARS News Service <NewsService@ars.usda.gov>
Date: Wed, 03 Dec 2003 08:56:30 -0500
To: ARS News subscriber <lonrom@hevanet.com>
Subject: Disease-Resistant Citrus Rootstocks

STORY LEAD:
ARS Developing New, Disease-Resistant Citrus Rootstocks

___________________________________________

ARS News Service
Agricultural Research Service, USDA
Alfredo Flores, (301) 504-1627, aflores@ars.usda.gov
December 3, 2003
___________________________________________

Three new citrus rootstocks developed by the Agricultural Research
Service have emerged as strong candidates to help the U.S. citrus
industry combat key diseases and the citrus root weevil.

The new rootstocks, called US-897, US-942 and US-802, were developed at
the ARS U.S. Horticultural Research Laboratory in Fort Pierce, Fla.
Geneticist Kim D. Bowman, based at the lab, has been managing the
agency's effort to develop new citrus rootstock for more than 10 years.

ARS research on citrus rootstocks goes back more than a century. It's
only been in recent years, however, that the industry has felt an
urgency to deal with growing rootstock problems, such as those caused by
citrus tristeza virus, foot rot and root rot (Phytophthora species), the
Diaprepes abbreviatus root weevil and inadequate soil adaptation. The
citrus industry has a total economic impact exceeding $8 billion
annually in the state of Florida.

Over the past few years, ARS citrus rootstock development efforts have
been expanded and accelerated because of funding from the citrus
industry through grants from the Florida Citrus Production Research
Advisory Council. Collaborators are an important part of Bowman's
research effort, helping to test new rootstocks for resistance to
diseases and pests.

A quality rootstock can defend itself against these diseases and pests,
while producing a high yield of quality fruit sustained over a long
period of time--up to 50 years. Rootstocks are the bottom portions of
grafted trees, to which are spliced tops with branches from trees that
make the best fruit. These grafted trees produce citrus fruits much
quicker than seedling trees.  

All three of the top rootstocks are at least three to four years away
from commercialization, but they have performed well in initial tests in
damp coastal soil for combating Phytophthora nicotianae, P. palmivora
and the diaprepes citrus root weevil. These two phytophthora, combined
with diaprepes, can form a lethal combination that could devastate
Florida's citrus-producing regions.

Read more about this research in the December issue of Agricultural
Research magazine, available on the web at:
http://www.ars.usda.gov/is/AR/archive/dec03/citrus1203.htm

ARS is the U.S. Department of Agriculture's primary scientific research
agency.
___________________________________________

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