Combining Ability over Environments in Durum Wheat

Studies on combining ability pooled over three environments for the seven characters involving eight genetically diverse varieties/lines of durum wheat (Triticum durum Desf;) are reported. Both the general as well as specific combining ability variances were significant for all the investigated characters, viz. gram yield, spike number, grain number, spikelet number, grain weight, spike length, plant height and days to heading. The combined analysis revealed that the general combining ability components (GCA) were higher than those of specific combining ability components (SCA) for spikelets per spike, spike length, plant height and days to heading. However, for grain yield, spike number, grain number and grain weight the specific combining ability components (SCA) were observed to be of higher magnitude. In the case of grain yield exclusively, the magnitude of the SCA component was proportionately much higher than that of GCA component revealing specifically greater role of non additive gene effects for this attribute. The GCA x E interaction effects were significant for spikes per plant, spikelets per spike, spike length and days to heading, whereas for grain yield and grain number the SCA x E interaction effects were significant. However, for the attributes spike number and grain weight both the GCA x E and SCA x E interaction effects were significant. The parents MPO 306 and MPO 311 having been observed as good combiners for grain yield and certain component traits also, offer the best possibilities of exploitation for the development of improved lines. The cross combinations MPO 311 x HI 9015, MPO 306 x HI 9015, MPO 306 x JWJ 46 and MPO 311 x HI 9017 having shown significantly high specific effects for grain yield and certain component traits also could be expected to throw transgressive segregants and thus need exploitation in the breeding programmes. In view of parallel role of both additive and non-additive genetic effects determining the inheritance of different attributes, their simultaneous exploitation through adoption of biparental approach/early generation mating is advocated.