Interaction of virescent genes in upland cotton (Gossypium hirsutum L): Chlorophyll content

The interactions between the virescent genes nu(2) and nu(14) of cotton (Gossypium hirsutum L.) were determined and compared with other virescent genes. Single crosses were made among various virescent lines, and the progenies were tested from 1991 to 1994. Allelic tests established that nu(2) and nu(14) were nonallelic, but their F-1 hybrid plants were virescent, with phenotypic expression and chlorophyll content intermediate between the parents. In the F-2 population, plants segregated into classes with various degrees of virescent expression - from green, parental virescents, deep yellow, to chlorotic types with extremely low vigor. The chlorophyll content of functional leaves on the deep-yellow type (0.54-0.56) was less than one-half that of the parental virescent types (1.13-1.43). The interaction effect between nu(2) and nu(14) was prominently reflected in the reduced content of C-b and the high C-a/b ratio of the deep-yellow type. This complementary function can be due to the nondiploidized function of homoeologous loci of the G. hirsutum allotetraploid.