| On the basis of degree of divergence (D2), 94 populations
could be grouped into 11 clusters (Table 1). Cluster
I and II were the largest and included 6 parents and 54 hybrids. Rest 16
parents and 18 hybrids scattered over 9 groups mainly added to the divergence.
This corroborated the findings of SRIVASTAVA & ARUNACHALAM (1977), that
only few hybrids could add substantial variation in the population. Groups
IX, X and XI were monogenotypic and comprised of genotypes which were extraordinary
for one or more characters. In general, intracluster distances (Table
2) were almost equal and lower than the intercluster distances. Thus,
the genotypes included, within a cluster tended to diverge less from each
other possibly due to large similarity in parentage or selection of genotypes.
The inter cluster distances varied from 7.4 between group I and III to 16.6
between VIII and XI. Cluster VIII, in general, was more divergent from all
other clusters because the genotypes included were very late in ear emergence,
dwarfest in height and had maximum tillers per plant. The cluster means showed appreciable differences for several characters among single as well as multigenotypic clusters. However, the differences were more clear for days to ear emergence, plant height, grains per spike, floret fertility, 1,000 grain weight and grain yield (Table 3). F1 hybrid Tc 13 x UPT 74535 included in cluster XI was good for 1,000 grain weight, grain crushing hardness, grain density and grain yield, while genotypes grouped in cluster VII were good for grains per spike, floret fertility and harvest index and in group II for protein content, biological yield per plant and grain yield. Inclusion of these genotypes in hybridization programme would, therefore, be worth while. Most of the characters appeared to contribute almost equally to the total divergence. However, plant height (11.0%), spike length (9.0%), days to ear emergence (8.7%) and 1,000 grain weight (8.6%) appeared to contribute relatively more, while grain crushing hardness being the lowest (5.0%). The clustering pattern of the hybrids is known to be influenced by their parentage because of close affinity between the parents and progeny (CHAUDHARY & SINGH 1975). In present study also, mainly three grouping trends were evident. Out of 72 hybrids, 34 were grouped in different clusters than both the parents. Such a grouping behaviour of F1 hybrids may be explained on the basis of genic interactions, among parents. In other 32 cases, hybrids were found to be grouped with one of the parent which showed dominance in its favour. In rest 6 cases, F1's and their parents were clustered together. Such cross combinations depicted relatively low genetic divergence among parents. The importance of genetic diversity among parents entering crosses has been duly emphasized (BHATT 1973). However, in present study, genetic divergence among parents did not reveal any consistent relationship with grain yield potential of their hybrids. Despite the large differences for D2-values among parents in cross T103 x 6TA204 (107,2) and Koala x TL-22 (15.6), the perse performance of both these F1 hybrids was same (33.0 g/plant). It appeared that the genotypes with restricted genetic divergence and falling in the same clusters may also produce desirable hybrids provided they compliment the major weaknesses of each other as against those involving genotypes which fall in distant clusters and are supposed to have wide genetic divergence. In that context, four crosses ; T130 x 6TA204, T103 x 6TA204, TL56 x St69-1 and Koala x TL-22 figured important for further breeding programmes. References AHMAD, Z., KATIYAR,R.P. & SHYAM, R. 1980. Genetic divergence in triticale. Indian J. Genet.,40 : 35- 38. BEHL, R.K., SAREEN, P.K. & PARODA, R.S. 1985. Male sterility mediated gene flow from wheat to triticale. II. Simultaneous improvement of triticale and wheat. Recent Advances in Pollen Research 3 : 329-343. BEHL, R.K., SINGH, V.P. & NAIDU, M.R. 1985. Genetic drvergence in hexaploid triticale. Intern. J. Tropi. Agri. 3 : 265-272. BHATT, G.M. 1973. Comparison of various methods of selecting parents for hybridization in common bread wheat. Aust. J. Agric. Res. 24 : 457-464. CHAUDHARY, B.D. & SINGH, V.P. 1975. Genetic divergence in some Indian and Exotic barley varieties and their hybrids. Indian J. Genet., 35 : 409-412. MUNTZING, A. 1979. Triticale, results and problems. Forts chritte der Pflanzenzuchtung., 10 : 1-103. RAO, C.R. 1952. Advanced Statistical Methods in Biometric Research. John Wiley and Sons, Inc., New York. SRIVASTAVA, P.S.L. & ARUNACHALAM, V. 1977. Heterosis as a function of genetic divergence in triticale. Z. Pflanzenzuchtung, 78 : 269-275. |
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