Economic Heterosis in Relation to Heterotic Parameters in Spring Wheat

Heterosis was worked out over superior and best parents in 45 F₁s derived from 10 X 10 diallel mating design. Out of six included commercial varieties of high yield potential, HD 1949 was utilized as best parent for estimating economic heterosis. Twenty one and 11 crosses exhibited positive and significant heterobeltiosis and economic heterosis respectively. The hybrids, ‘HD 1949’ X ‘SP 1’, ‘HD 1949’ × ‘K 65’, ‘K 65’ × ‘Kalyansona’, ‘K 816’ × ‘Hyb 65’ and ‘SP 1’ X ‘Kharchia’ manifested significant heterosis, and specific heterotic response (except for ‘SP 1’ × ‘Kharchia) and high magnitude of inbreeding depression for grain yield involving mostly HD-1949, K 65 or SP 1. These parents had dominant genes for grain yield except for HD 1949. These had also poor additive effects for grain yield. The economic increase in grain yield happened to be due to non-additive genetic component as was confirmed by the presence of dominant genes for yield in the parents. Therefore, these crosses may be suitable for heterosis breeding. The other cross combinations, ‘HD 1949’ × ‘Kharchia’, ‘K 853’ × ‘Kharchia’, ‘HD 1949’ × ‘NI 5643’, ‘Kalyansona’ × ‘Kharchia’, ‘Hyb 65’ × ‘NI 5643’ and ‘HD 1949’ × ‘Hyb 65’ showed significant heterosis and heterotic response (except for ‘Hyb 65’ × ‘NI 5643’) involving mostly ‘Kharchia’, ‘HD 1949’, ‘Hyb 65’ or ‘NI 5643’. This increase was due to significant contribution of both economic hetrotic response and additive effects of the parents for five to six desirable traits. Among them ‘HD 1949’ × ‘NI 5643’ and ‘K 853’ × ‘Kharchia’ had 23⋅41 and 31⋅67 per cent of economic heterosis, respectively and corresponded to 4⋅27 and 6⋅71 per cent for inbreeding depression. The increased heterotic response of these two F₁s may principally be due to accumulation of favourable additive genes and complementary and duplicate epistasis which may be fixable. Such crosses are expected to throw more superior segregants owing to their balanced homeostatic system than their respective superior parents and may be improved further by mass selection followed by recurrent method of breeding.