Influence of water availability on fertility restoration of CMS lines with the 'M35', A4 and '9E' CMS-inducing cytoplasms of sorghum

Male fertility restoration in new types of sorghum cytoplasmic male sterility-inducing cytoplasms (A4, '9E', 'M35'), characterized by the formation of non-dehiscent anthers, is difficult. Lines with fertility-restorer 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, '9E', A4 and 'M35', 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, '9E' and 'M35' 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 'switches on' 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 'M35' 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.