July
1999
, Volume
83
, Number
7
Pages
681
-
684
Authors
X. H.
Lai
,
Visiting Senior Scientist, Texas Agricultural Experiment Station, Beaumont, TX 77713
;
M. A.
Marchetti
,
Research Plant Pathologist, U.S. Department of Agriculture, Agricultural Research Service, Texas A&M University Agricultural Research and Extension Center, Beaumont, TX 77713
; and
H. D.
Petersen
,
Regional Biometrician, U.S. Department of Agriculture, Agricultural Research Service, Southern Plains Area, 7607 Eastmark Drive, College Station, TX 77840
Affiliations
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Accepted for publication 5 April 1999.
Abstract
ABSTRACT
Evaluation of rice for resistance to rice blast disease caused by Pyricularia grisea usually is conducted in upland (nonflooded) disease nurseries, although all commercial U.S. rice is produced under flood irrigation. Upland rice is more susceptible to leaf blast than is flooded rice, and the magnitude of this differential susceptibility can vary among cultivars. This 2-year study was undertaken to determine (i) the relationship between rates of disease development (slow-blasting) in upland and flooded rice and (ii) the value to a rice breeding program of establishing a flooded blast nursery, a facility far more difficult to manage than an upland nursery. Among 200 rice lines compared for leaf blast susceptibility under upland and flooded cultures, only 7 were rated as slightly more resistant under upland culture and 136 rated more resistant under flooded culture. Disease ratings under upland and flooded cultures were highly correlated (R = 0.819). Among 14 preselected cultivars over 2 years, disease development curves under upland and flooded cultures were highly correlated (R = 0.990). The cultivars with intermediate susceptibility under upland culture appeared to benefit most from flooded culture. Upland culture provided more opportunities to assess slow-blasting than did flooded culture, since many lines that produced susceptible-type lesions in upland culture failed to do so under flooded culture. It was concluded that adequate information on comparative leaf blast resistance among rice lines was attainable from upland blast nurseries and that routine evaluation of rice breeding lines for blast resistance in flooded nurseries was not necessary.
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ArticleCopyright
The American Phytopathological Society, 1999