R.K. BEHL and V.P. SINGH
Haryana Agricultural University, Hisar-125004, India.
Extent of genetic diversity in parental stocks largely determines the inherent potential of a cross. Hybrids between highly diverse parents are expected to show high heterosis in F1 and wide spectrum of variability in segregating generations. On the other hand, low pace of progress in triticale improvement programmes has been attributed to its narrow genetic base and unlike other cereals, improvement work in triticale has to be preceded by creating variability (MUNTZING 1979 ; BEHL et al. 1985). Therefore, quantitative assessment of degree of divergence among genotypes entering crosses and their hybrids is essential. However, such reports in triticale are scanty (SRIVASTAVA & ARUNACHALAM 1977 ; AHMAD et al. 1980 ; & BEHL et al. 1985). Present study was, therefore, conducted to determine genetic divergence among 72 F1 hybrids and their 22 parents.
Materials and Methods
Twenty two strains of hexaploid triticale, selected on the basis of genetic divergence (BEHL et al. 1985), were crossed into line (female) x tester (male) matings using 18 lines and 4 tester to yield 72 F1 hybrids. Ninety four genotypes (parents and hybrids) were evaluated in randomized block design with three replications. Observation on randomly selected five plants per plot in each replication were recorded on 14 characters related to plant morphology and components of grain yield and quality.
Mahalanobis's D2-statistic was used for assessing genetic divergence among genotypes. The original variables (X'S), which were inter correlated, were transformed into a set of mutually uncorrelated variables (Y'S, linear functions of X'S) by pivtol condensation method (RAO 1952). Then, the D2 value between two strains is given by the simple sum of squares of differences in Y'S as shown by
The genotypes were grouped into a number of clusters using generalized statistical distance
according to Tocher method (RAO 1952). The
per cent contribution of a character towards genetic divergence was calculated
as the percentage of combination in which the characters ranked first. Results and Discussion
Analysis of variance revealed significant differences among parents, hybrids and parents vs hybrids, suggesting thereby sufficient amount of genetic variability. This was further substantiated by the fact that D2-values for 4371 combinations among 94 genotypes ranged from 5.5 between T 24 and Armadillo x 6TA 204 to 326.4 between Tc13 x St69-1, whereas, such a range among parental combinations was from 10.74 (T125) to 178.20 (UPT 74418). Thus, considerable increase in variation spectrum was added after hybridization between parental stocks.