YIELD STABILITY, GENOTYPHIC AND PHENOTYPIC CORRELATIONS AMONG YIELD CONTRIBUTING TRAITS IN SPRING WHEAT UNDER TWO ENVIRONMENTS

Nine widely grown wheat cultivars and an advance line, representing three major wheat breeding programs of the Khyber Pakhtunkhwa (Pakistan), were field evaluated at Cereal Crops Research Institute (CCRI), Pirsabak (Nowshera) and Agricultural Research Station, Baffa (Mansehra) during 2007-08 crop season. A randomized complete block design with four replicates was used at each location. The two test locations differed significantly for plant height, grains spike^-1, biological yield and grain yield, however, differences among locations were non-significant for spike length, spikelets spike^-1 and 1000-grain weight. Highly significant genetic diversity among the wheat cultivars was evident for all traits via independent analysis of variance for each location as well as across locations, but cultivar x location interactions existed for plant height (P ≤ 0.05), spikes m^-2 (P ≤ 0.01) and grain yield (P ≤ 0.01) only. Plant height, grains spike^-1, biological yield and grain yield of the cultivars/advance line averaged as 102.5 vs. 104 cm, 59 vs. 55, 10467 vs. 9878 kg ha^-1 and 3914 vs. 3127 kg ha^-1 at Mansehra and Nowshera, respectively. Generally the wheat cultivars released by the CCRI, Pirsabak excelled the group for mean grain yield across locations: Pirsabak-2005 (4195 kg ha^-1), PR-87 (4062 kg ha^-1) and Saleem-2000 (4023 kg ha^-1). Phenotypic and genetic correlations among yield related traits were generally of similar magnitude and nature at both locations. Positive significant phenotypic association existed of spike length with spikelets spike^-1 and grains spike^-1; of spikelets spike^-1 with grains spike^- 1; of spikes m^-2 with 1000-grain weight, biological yield and grain yield; of biological yield with spikes m^-2 and 1000-grain weight; and of grain yield with spikes m^-2, 1000-grain weight and biological yield both at Nowshera and Mansehra. Positive genetic association was observed of spikelets spike^-1 with grains spike-1; of spikes m^-2 with 1000-grain weight; and of biological yield and grain yield with spikes m^-2 and 1000-grain weight at both locations.