Use of SPAD chlorophyll meter to screen sorghum (Sorghum bicolor) lines for postflowering drought tolerance

The experiments were conducted in the postrainy seasons during 2006-07 and 2007-08 to examine the relationship of chlorophyll concentration by using SPAD chlorophyll meter with yield components in 20 sorghum (Sorghum bicolor L. Moench) lines grown under irrigated and un-irrigated water regimes imposed during the postflowering growth period. Significant genotypic variations were recorded for SPAD chlorophyll meter reading total dry matter, panicle dry weight and grain yield under both water regimes. The SPAD chlorophyll meter reading is significantly related with plant height, total dry matter, panicle weight and grain yield, but no relation was observed with days to flowering. Significant reductions in SPAD chlorophyll meter reading, total dry matter, panicle weigh( and grain yield under non-irrigated conditions were recorded. The minimum reductions in SPAD chlorophyll meter reading (5.7-15%), total dry matter (19.7 31.1%), panicle dry weight (0.8-13.1 %)and grain yield (10.5-15.5%) under un-irrigated conditions were recorded in 'S 35% 'Parbhani Jyoti', 'SLB 9', 'Mauli', and 'Parbhani moti'. The strong relationship between drought sensitivity index and per cent change in SPAD chlorophyll meter reading under water deficit conditions indicates that higher chlorophyll concentration is vital for adaptation to water deficit conditions during postflowering growth period. Significant and grain yield (R(2) =0.67) and positive relationships of SPAD chlorophyll meter reading with total dry matter (R(2) =0.42) suggest that selection using SPAD chlorophyll meter reading will have 42-67% probability in selecting genotypes with higher total dry matter and grain yield.