Department of Plant Breeding and Genetics, Chandra Shekhar Azad University of Agriculture and Technology, Kanpur, 208 002, India
Heterosis, inbreeding depression and combining ability were estimated in a 10 × 10 diallel in first and second filial generations, involving diverse height categories of spring wheat, belonging to tall, d1, d2 and d3 groups. Grain yield exhibited maximum heterosis (45∙21%) over superior parent followed by 1,000-kernel weight (39∙31%), number of grains per spike (25∙78%), number of productive tillers (22∙98%), number of spikelets per spike (4∙59%) and plant height (−4∙25%). Manifestation of heterosis for yield was through kernel weight, number of grains per spike and effective tillers per plant. The intermediate height categories (d2 and d1) reflected superiority over other height categories with high heterosis and considerably less inbreeding depression for yield and some yield contributing attributes. Combining ability analysis also showed superiority of d2 and d1 height groups for their good and desirable g.c.a. effects for grain number per spike and productive tillers per plant. Non-additive variation was predominant for all the traits but substantial amount of additive variances was also present. Semidwarfs (d3) were consistently showing negative g.c.a. effects for plant height, 1,000-kernel weight and grain yield except HD 1949 for yield. In general, the four categories of height could not be directly related to any consistent trend in the magnitude of g.c.a. effects for number of productive tillers per plant and number of spikelets per spike.
