STUDIES ON HETEROSIS, COMBINING ABILITY AND GENE ACTION USING L X T ANALYSIS IN PEARL MILLET [Pennisetum glaucum (L.) R.Br.]
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Date
2004-09
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JAU, JUNAGADH
Abstract
An investigation was carried out with a view to estimate the nature and magnitude of heterosis, combining ability and gene action for grain yield and its attributes through line x tester mating design involving 8 females and 10 pollinators. The resultant 80 cross combinations along with their parents and two checks viz GHB - 558 and MH -169 were evaluated at Main Millet Research Station J.A.U. Jamnagar during Kharif 2002 in a randomized block design with three replication.
The mean squares due to genotypes, parents and hybrids were found highly significant, revealing the presence of sufficient variability in the experimental material. The highly significant mean squares due to parents vs. Hybrids for all the characters except length of protogyny, ear head girth and number of effective tillers per plant, suggested the existence of conspicuous heterosis.
The magnitude of heterosis varied from cross to cross for all the characters. The high level of heterosis was observed for grain yield, fodder yield, ear head weight per plant, earhead length, number of effective tillers per plant, number of nodes per plant, plant height and harvest index, while least heterosis was found for days to maturity and length of protogyny. Days to 50% flowering, earhead girth, 1000 seed weight and threshing index exhibited moderate heterosis.
The number of crosses showing heterobeltiosis in grain yield were large with very high magnitude, although the number of cross combinations displaying heterobletiosis in various yield attributing characters were small with comparatively low magnitude revealing there by the suitable combinations of yield attributes resulting in more favourable complementation and mutual compensation for manifesting grain yield.
Combining ability analysis revealed importance of both additive and non-additive types of gene action. However, high sca/gca ratio for grain yield, fodder yield, earhead weight, number of effective tillers per plant, length of protogyny and threshing index suggested the predominant role of non additive gene action in the inheritance of these characters, which favoured a hybrid breeding programme. Preponderance of additive gene effect was found for days to 50% flowering, number of nodes per plant, plant height, earhead length, earhead girth and harvest index while equal prevalence of both for days to maturity and 1000 seed weight.
The estimates of GCA suggested that none of the parents was found to be good general combiner for all the characters. Female parent ICMA- 98333 and male parents IPC -1518 and J-2290 are identified as the best general combiners, by virtue of very good general combining ability for grain yield along with a minimum of eight yield attributes. They may be further exploited for future pearl millet improvement programme.
Seven most promising hybrids were identified for grain yield based on magnitude of standard heterosis over check–GHB-558. The cross combination ICMA-98333 x IPC-1518 accomplished the top rank followed by JMSA-2005 x IPC-1501, ICMA-00777 x IPC-1518, ICMA-98777 x J-2290 , ICMA-98333 x J-2290, JMSA-20021 x J-2290 and ICMA-00777 x J-2290 respectively. All the above mentioned most heterotic hybrids exhibited positive heterobeltiosis and good SCA effects for grain yield except the hybrid ICMA-98333 x J-2290 having average SCA effects but involving both parents with high per se performance and good GCA effect. Further, the top seven specific cross combinations exhibited significant positive heterobeltiosis and good per se performance. This indicated an association among heterosis, combining ability and per se performance to some extent suggesting there by the consideration of all the three aspects in selecting superior cross combination.
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