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Improvement of nutritional value of crops is one of the main goals of plant biotechnology. These studies are extremely important for sorghum-a unique drought-tolerant cereal crop that is of special importance for sustainable grain production in the arid regions. The major cause of relatively low nutritive value of sorghum grain is the resistance of one of its seed storage proteins, γ-kafirin, to protease digestion. Using Agrobacteriummediated genetic transformation, we have obtained transgenic sorghum plants harboring a genetic construct for RNA interference (RNAi) silencing of the γ-kafirin gene. In T 1 generation, transgenic plants with modified endosperm texture were found. These plants had lowered level of the 28-kDa γ-kafirin protein and kafirin oligomers, which are formed by natural kafirin polymerization. In vitro protein digestibility analysis showed that the amount of undigested protein in transgenic plants was reduced by 2.9-3.2 times, in comparison with the original line, the digestibility index reached 85-88% (60% in the original line). HPLC analysis showed that total amino acid content in transgenic plants was reduced, while the lysine proportion was increased by 1.6-1.7 times. PCR analysis confirmed inheritance of the genetic construct up to T 4 generation.

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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.