The Evaluation of High Tannin Cotton Lines for Resistance to Rhizoctonia solani and Pythium aphanidermatum

Abstract

Cotton seedling disease complex is caused by a number of pathogens inducing similar symptoms and can lead to thin, uneven stands that grow slowly and yield poorly. Preliminary work indicated that a set of high tannin cotton lines developed and released in 1989 by Texas A&M AgriLife Research, (Smith et al., 1990a, Smith et al., 1990b, Schuster et al., 1990) may possess increased resistance to disease. This evidence, along with additional studies that show a clear role of tannin in disease resistance, suggest that these high tannin cotton lines may prove useful in breeding for increased resistance to cotton seedling disease complex. High tannin cotton lines were screened for their resistance to Rhizoctonia solani and Pythium aphanidermatum. While no high tannin germplasm line was more resistant to R. solani than the resistant control, Tamcot SP 21, the potential for significant gains from selection was demonstrated. Fifteen high tannin lines expressed resistance to P. aphanidermatum equal to the resistant control, Tamcot Sphinx (El-Zik and Thaxton, 1996). This resistance was not shown to be correlated with tannin content, though it is still unclear whether or not this lack of correlation is real or due to limitations in measuring tannin in infected seedlings.