Monday, November 13, 2006

Planting Date Effects on Pod Yield and Symptoms of Tomato Spotted Wilt Virus in Peanut.

Barry Tillman1, Daniel Gorbet2, and Peter Andersen2. (1) University of Florida, Univ. of Florida, 3925 Hwy 71, Marianna, FL 32446-7906, (2) N. Florida Res. & Educ. Center, 3925 Hwy. 71, Marianna, FL 32446

Date of planting and cultivar resistance are two of the primary control measures for spotted wilt of peanut caused by Tomato Spotted Wilt Tospovirus (TSWV).  The current University of Georgia TSWV Risk Index considers risk high if planted prior to 1 May, moderate if planted 1 May  to 10 May, least if planted 11 May to 25 May and moderate to high if planted after 25 May.  We evaluated the reaction of ten peanut cultivars with differing levels of spotted wilt resistance when planted within the high, least and late moderate windows during 1998, 1999, and 2000 near Marianna, Florida.   Pod yield and spotted wilt severity were measured each year.   In all genotypes, pod yield varied in a quadratic trend with the highest yield occurring when planted in May.   In six of ten genotypes, spotted wilt ratings varied linearly with planting date with less disease in June plantings and more in April plantings.  However, in ‘Florunner’, one of the most susceptible genotypes, spotted wilt was greatest in June planting and least in May planting, and a similar numerical trend was noted for the other susceptible genotype ‘SunOleic 97R’.  In years when spotted wilt is not too severe such as 1998 and 2000, our data show that peanut pod yield potential is greatest in May plantings and risk of TSWV is least in June plantings.  This indicates that disease is not the overriding factor in pod yield in those years.  However, in 1999, when spotted wilt was measurably worse than in 1998 or 2000, June plantings produced the highest pod yield and the least spotted wilt.   This indicates that severe spotted wilt can override the biological pod yield advantage of May plantings.