Male fertility restoration in new types of sorghum cytoplasmic male sterility-inducing cytoplasms (A4, Ô9EÕ, ÔM35Õ), characterized by the formation of non-dehiscent anthers, is difficult. Lines with fertilityrestorer genes for these unique cytoplasms do occur, but rarely, and when found tend to be unstable in their inheritance and expression. The aim of this research was to explore reasons for this instability. Seven lines in three unique cytoplasms, Ô9EÕ, A4 and ÔM35Õ, and six lines that restore with these cytoplasms were grown at the Agricultural Research Institute for South-East Region in Saratov, Russia from 1993 to 2004. Levels of male fertility restoration and various environmental factors were recorded. It is reported that for sorghum hybrids in the A4, Ô9EÕ and ÔM35Õ male-sterile cytoplasms, the level of plant male fertility is determined by the level of water available to plants during anther and pollen formation that which Ôswitches onÕ the expression of fertility-restoring genes, and is possibly involved in an unusual type of male fertility inheritance in these cytoplasms. The creation of reliable line-fertility restorers capable of the restoration of male fertility of F 1 hybrids in ÔM35Õ cytoplasm under conditions of water stress is also reported. Current research explore mechanisms involved possible in responses to water levels at various growth stages and their influence on fertility within these cytoplasms.
A high frequency of male sterile mutants regeneration was shown in callus cultures derived from leaves and panicles of haploid sorghum (Mscl, A1 cytoplasm) and a spontaneous autodiploid obtained from this haploid. The cultures derived from the embryos of this autodiploid yielded significantly fewer mutants. Absolutely or partially male sterile mutants appeared among the regenerants or in the progeny of fertile regenerants. In the self-fertilized progenies of partially male sterile mutants and in the hybrids of sterile mutants with autodiploid line (i.e. under one and the same nuclear genome) male sterility mutations were inherited as cytoplasmic. Non-Mendelian segregation of sterile, partially male sterile and fertile plants was observed in these progenies. Partially male sterile plants were characterized by somatic segregation of male sterility genetic factors. In test-crosses with some CMS A1 fertility restorers, mutations were manifested as nuclear recessive while with others as nuclear dominant. These differences are supposed to be the result of interaction of fertility restorer genes of these testers with the novel cytoplasm. Male sterility mutations accompanied with female sterility were inherited as nuclear recessives.
Conditions for the effective experimental regulation of ploidy level in regenerants from callus cultures derived from young, undifferentiated leaves and panicles of haploid sorghum were established. Diploidization depended on the ontogenetic age of the explant and the 2,4-D concentration in the medium. With a low 2,4-D concentration (0.5 mg/l) and segments of young panicles (< 35 mm long) the cultures produced only haploid regenerants. Diploid plants were formed from cultures derived from more mature panicles (> 35 mm long) and young leaves (15-65 mm long). Under a high 2,4-D concentration (2.5 mg/l) diploid plants were regenerated from cultures derived from young panicles (less than 35 mm) except the most young ones (5-15 mm). The majority of the diploid regenerants contained mutations, mainly affecting male fertility and plant height.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.