Development of Fertility-Restoring Lines for 9E Type CMS of Sorghum Using Environmentally Induced Fertility Revertants

Development of reliable fertility-restoring lines is the most important prerequisite for using cytoplasmic male sterility (CMS) in plant breeding. Sorghum 9E type CMS is characterized by unstable expression of fertility-restoring genes, which require high levels of water availability for plants during microsporogenesis and flowering. In order to create reliable male-fertility-restoring lines for 9E type CMS, the progeny of test crosses of fertile revertant lines in 9E cytoplasm, which were obtained as a result of reversions in sterile F1 hybrids induced by conditions of high water availability, with CMS lines in this cytoplasm were grown in selective backgrounds: in the dry plots and in the plots with additional watering as well as in the field under natural moisture supply. In the majority of hybrid combinations, fertile plants were observed only when additionally watered during the flowering period. F1 hybrids with different CMS lines with 9E cytoplasm significantly differed in terms of the degree of restored fertility and the response to water availability conditions. Fertile plants predominated in the F2 families; in different hybrid combinations, the ratio of restored and sterile plants corresponded to 3 : 1 or 13 : 3 segregation. After selection in the drought conditions of the fertile plants from the offspring of hybrids from the cross of the CMS line 9E Pishchevoe 614 and male-fertile revertants, two lines were obtained that were able to restore fertility of F1 hybrids in field conditions.