Understanding the genetics of physiological traits to achieve next breakthrough in bread wheat (Triticum aestivum L.)

Abstract

Optimization of different physiological processes to meet the requirement of various agronomic traits consolidation now appears to be necessary to break the fast-approaching yield ceiling. Source-sink relationship in the new high-yielding genetic base, along with better partitioning of assimilates toward developing grain, requires synergy between various developing traits at the physiological level. In the current study, eight lines with improved genetic base for the grain yield with diverse physiological traits were crossed in a diallel fashion to generate 64 crosses. The F1s were grown along with their parents to study their physiological behavior vis-a-vis combining ability. All the physiological traits are controlled by both additive and non-additive gene action with strong maternal effects. HDCSW18(P8) and HD 3226(P6) were found be good general combiners for grain yield. HDCSW18 was found to be the best general combiner for a majority of physiological traits like crop growth rate (CGR), leaf area index (LAI) and NDVI, along with grain yield. DBW 187 was found to be a good combiner for photosynthetic efficiency and may complement well with HDCSW18 for developing a highly physiologically efficient genotype. Strong deviation in expression from normal expected value in F1 combinations for grain yield was realised in cross combinations 35th ESWYT-147 (P2) X HDCSW18 (P8) for CGR, NIAW34/PHW12//43IBWSN-1187(P3) X HDCSW18(P8) for canopy temperature depression, NDVI, NIAW34/PHW12//43IBWSN-1187(P3) X HD 3226(P6) for LAI, DBW187 (P5) X HD3086(P7) for chlorophyll content, and in 35th ESWYT-147(P2), XHDCSW18 (P8) and NIAW34/PHW12//43IBWSN-1187(P3) XDBW187 (P5) for grain yield, respectively. More than 10% standard heterosis in DBW187(P5) X HDCSW18(P8), NIAW34/PHW12//43IBWSN-1187(P3) XDBW187 (P5) and HD3117 (P1) X HD2967//HD2887/HD2946//HD2733 (P4) for grain yield seems to be mainly because of highly improved leaf area index and grain weight. The high proportion of non-additive components in the genetic control of yield and harvest index offers us an opportunity either for exploitation of heterosis by developing hybrids or improvement in these traits by following a population improvement program. The presence of significant and positive standard heterosis for each of the physiological traits in at least one of the crosses offers an opportunity to develop physiologically improved fixed lines with a higher probability of higher grain yield.