Characterization of kafirin composition and in vitro digestibility in CMS-lines, fertility restorers and F1 hybrids with the new types of CMS-inducing cytoplasms of sorghum

P>One of the reasons of poor nutritive value of sorghum grain is resistance of its seed storage proteins (kafirins) to protease digestion. To reveal sorghum entries with increased kafirin digestibility, the sodium dodecyl sulfate - polyacrylamide gel electrophoresis (SDS-PAGE) of endosperm proteins of 10 lines [cytoplasmic male sterility (CMS)-lines and fertility restorers] and five F-1 hybrids before and after pepsin digestion was carried out. For quantitative estimation of kafirin digestibility the SDS-PAGE banding patterns were scanned by laser densitometer. Significant variability for both individual fractions and total kafirin digestibility was found. The line KVV-45, fertility restorer for the Indian 'M35-1A' type of CMS, had the highest level of kafirin digestibility (30% and 25% of undigested gamma- and alpha(1)-kafirins, respectively), while in some entries 80-90% of kafirins remained undigested. Increased alpha(1)-kafirin digestibility coincided with relatively high gamma-kafirin digestibility. High-molecular weight kafirins (HMWK) (45 kDa and 66 kDa) resistant to pepsin digestion were found in some lines, the F-1 hybrids had the same HMWK as parental lines. These data demonstrate possibility for isolation of sorghum genotypes with increased nutritive value by screening their flour for in vitro protein digestibility.