VARIATION IN DROUGHT SUSCEPTIBILITY AMONG CLOSELY-RELATED WHEAT LINES

Drought resistance is a complex trait for which systematic improvement has been difficult. One means of simplifying analysis of such a trait is through examination of variability among closely related genotypes . Sister lines of wheat exhibiting significant variation for rainfed y ield, irrigated yield, and a drought susceptibility index, S, were ide ntified among derivatives of a backcross breeding program. Of seven si ster lines compared in a 2-y field study at Bushland, Texas, three wer e found significantly less susceptible than a related cultivar, TAM-10 7, two were significantly more susceptible than TAM-107 and two were n ot distinguishable from TAM-107. Relatively small, but significant, va riability was observed among the lines for developmental variables, in cluding anthesis date, date of physiological maturity and length of th e grain-filling period. No meaningful correlations could be establishe d, however, between developmental variables and yield or susceptibilit y index. While some differences may exist among these lines in mechani sm underlying relative drought susceptibility, lack of correlation wit h developmental variables indicates that this set of lines may be valu able in identifying useful drought resistance mechanisms in wheat.