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Six high yielding and rust resistant bread wheat parents were crossed in a diallel fashion to get all possible combinations (30 crosses). Heterosis and heterobeltiosis analysis was performed for morpho-physiological traits like, stomatal frequency, leaf venation, flag leaf area, specific flag leaf weight, days to heading, tillers per plant, plant height, spike length, grains per spike, 1000-grain weight, biomass per plant and grain yield per plant under irrigated and drought stress conditions. Significant mid and better parent heterosis values were observed in certain single crosses for all traits under both environments. The maximum heterosis of 36.39, 15.17 and 12.54 per cent was noted for grain yield per plant, tillers per plant and spike length, respectively, in cross LU26S X Roh.90 under irrigated conditions, whereas cross combination Inq.91 X 4072 manifested maximum heterosis and heterobeltiosis for 1000-grain weight under irrigated and drought stress conditions. The presence of heterosis suggests that high yielding wheat hybrids can be developed.

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This paper describes the association, direct and indirect effects of morphological traits under drought stress and irrigated conditions. Significant mean squares among crosses were obtained for all characters under irrigation as well as drought stress. Positive and significant correlations were observed between grain yield per plant and flag leaf area, specific flag leaf weight, tillers per plant, peduncle length, spike length, grains per spike, 1000-grain weight, grain weight of mother shoot, biomass per plant and harvest index. Negative and significant correlation was noted for days to heading and grain yield per plant. Positive direct effects were exhibited for specific flag leaf weight, days to heading, tillers per plant, spikelets per spike, grain weight of mother shoot, biomass per plant and harvest index on grain yield while maximum indirect effects were observed through grain weight of mother shoot on grain yield for flag leaf area, days to heading, peduncle length, spike length, grains per spike, 1000-grain weight, biomass per plant and harvest index under irrigated conditions. In case of drought stress conditions, grain yield was positively and significantly correlated with flag leaf area, specific flag leaf weight, plant height, peduncle length, spike length, grains per spike, 1000-grain weight, grain weight of mother shoot, biomass per plant and harvest index. Similar to irrigated conditions days to heading has also negative and significant correlation with grain yield. Positive direct effects were observed for leaf venation, flag leaf area, days to heading, plant height, spike length, grains per spike, 1000-grain weight, biomass per plant and harvest index whereas positive indirect effects through biomass per plant on grain yield for leaf venation, plant height, spike length, grains per spike, 1000-grain weight, grain weight of mother shoot were observed under drought stress conditions. It is suggested that direct selection could be made for days to heading, tillers per plant, spikelets per spike, grain weight of mother shoot, biomass per plant and harvest index for the improvement of grain yield per plant and indirect selection through grain weight of mother shoot for spike length, grains per spike 1000-grain weight under irrigated conditions. Under drought stress conditions selection could be made for leaf venation, flag leaf area, days to heading, plant height, spike length, grains per spike, 1000-grain weight, biomass per plant and harvest index and indirect selection via biomass per plant for leaf venation, plant height, spike length, grains per spike, 1000-grain weight and grain weight of mother shoot.

Correlation and path-coefficient were computed on 10 bread wheat genotypes for plant height, flag leaf area, grains per spike, 100-grain weight, total dry matter of above ground material, total water used, evapo-transpiration efficiency, harvest index, water use efficiency and grain yield per plant. Highly significant differences were observed among the varieties/advanced lines for all the traits except water use efficiency, which was only significant. Grain yield was positively and significantly correlated with total dry matter, evapo-transpiration efficiency, harvest index and water use efficiency but non-significantly with plant height, flag leaf area, grains per spike, 100-grain weight and total water used. Maximum and positive direct effect (1.2956) was produced by water use efficiency and followed by total dry matter (1.286). While minimum negative direct effect was produced by 100-grain weight (-0.7902). Plant height, flag leaf area, 100-grain weight, total water used, evapo-transpiration efficiency and water use efficiency produced maximum positive indirect effects of 0.5313, 0.3390, 0.6495, 0.6985, 0.7382 and 0.4079 on grain yield through total dry matter, respectively. The traits having positive direct effects on grain yield, considered to be a suitable selection criteria for evolving high yielding genotypes. While in case of negative direct effects on grain yield, indirect selection criteria could be practiced through traits with positive indirect effects.