Heterosis in Inter-Varietal Crosses in Maize

Eight genetically diverse open-pollinated varieties and all their possible cross combinations inlcuding reciprocals, were studied at two agro-climatically different locations, viz., Bajaura and Palampur during kharif-1975. The experiment was laid out in randomised block design with three replications at both locations. The per cent heterosis over the mid-parent value was calculated by the method suggested by Walton (1971). The per cent heterosis over the better parent was calculated by the formula used by Liang et al. (1972). High heterosis over the better parent (40%) for yield was observed in the cross V₅ × V₇ at Bajaura and two crosses, viz., V_a × V₅ and V₈ × V₂ exhibited superiority of 41, 37% respectively, over better parent at Palampur. Two crosses, viz. V₅ × V₇ and V₂ × V₅, showed the maximum over all heterosis at the two locations. The hybrid V₅ × V₇, also exhibited 48% higher yield than the best local check (V₆) and on account of its being 5 days earlier in maturity also than the later, the results are of considerable practical importance. It was observed that, in general, the crosses showing superior heterosis values for yield also showed increased hybrid vigour in respect of ear length and ear diameter, but it was not true for the number of kernel rows per ear. The results showed that genetic as well as geographic diversity and contrasting endosperm types of parental varieties were associated with greater heterosis in the varietal crosses. It was also observed, that reciprocal hybrids should be evaluated along with straight crosses for maximum exploitation of heterotic effects.