Combining ability and heterosis in maize (Zea mays L.) crosses under normal and heat stress conditions
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Date
2018-02-06
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Department of Plant Breeding and Genetics, BAU, Sabour
Abstract
The present investigation entitled “Combining ability and heterosis in maize
(Zea mays L.) crosses under normal and heat stress conditions” was conducted at Maize Section of Bihar Agricultural University Sabour, Bhagalpur, Bihar (India). Twenty nine maize inbred lines were evaluated in normal (30th January, 2015) and heat stress (3rd March, 2015) conditions in Randomized Complete Block Design with objective to screen the maize inbred lines for heat tolerance on the basis of morphophysiological traits. The 13 SSR markers were used among 29 inbred lines with objective to study of molecular diversity among the inbred lines. During kharif, 2015 seven identified inbred lines i.e. five (CML 307,CML 306, CML 305, CML 411, CML 304) heat stress tolerant and two (CML 164, CML 25) heat stress susceptible were crossed in full diallel for making all possible 42 crosses. These forty two crosses, seven parents and two checks (DHM-117, SHM-2) were evaluated in a Randomized Block Design in normal (2nd January, 2016) and heat stress (15th March, 2016) conditions with objectives to determine general and specific combining ability of inbred lines and crosses, respectively and to estimate heterosis of crosses of inbred lines. Data were recorded on thirteen quantitative characters viz; days to 50 % anthesis, days to 50% silk, pollen viability, anthesis-silking ineterval, cell membrane thermo stability, plant height, ear height, days to 50 % physiological maturity, grain filling period, number of grains per plant, 500-grain weight, shelling per cent, grain yield per plant. The analysis of variance of maize inbred lines for the design of experiment in both the conditions and pooled analysis indicated highly significant mean squares due to genotypes for all the characters except pollen viability per cent in normal condition. In normal condition, the mean performance of inbred lines, namely, CML 308, CML 451, CML306, CML18 and CML 474; in heat stress condition, inbred lines, namely, CML 307, CML306, CML305, CML 411 and CML 304; and in pooled analysis inbred lines, namely, CML 307, CML306, CML 411, CML 304 and CML 305 were found to be top five rankers of grain yield per plant. The five inbred lines, namely, CML 307, CML 305, CML 306, CML 411 and CML 304 were categorized top five heat tolerant inbred lines due to their higher YSI and lower ASI values. Similarly, two inbred lines, namely, CML 164 and CML 25 were categorized highly heat susceptible inbred lines due to their lower YSI and higher ASI values. Level of polymorphism was found to be 100 per cent among the inbred lines for almost all the primers pairs except for phi062. The polymorphic information content value for the primer pairs ranged from 0.067 to 0.499. The inbred lines were characterized into two cluster ie I and II. The further cluster I was divided into two sub cluster i.e. cluster Ia and cluster Ib. Cluster Ia had five inbred lines whereas, cluster Ib had three lines. Cluster II had the highest number of twenty parents. The minimum Jaccard’s similarity co-efficient value was found between G9 and G23, whereas, on the other hand, the maximum Jaccard’s similarity co-efficient value was found between G2 and G3.The seven selected inbred lines [CML 164 (P1), CML 411 (P2), CML 305 (P3), CML 304 (P4), CML 25 (P5), CML 306 (P6) & CML 307 (P7)] on the basis YSI, were found to be genetically distinct among them. Analysis of variance revealed that the mean squares due to genotypes (seven parents and their 42 cross combinations and two checks) were found to be highly significant in both the conditions and pooled analysis for all the characters studied. In normal condition, the mean performance, crosses, namely, P4 x P1, P2 x P3, P1 x P2 and P2 x P1 ; in heat stress condition, crosses, namely, P4 x P1 and P2 x P7 ; and in pooled analysis, crosses P4 x P1 and P2 x P7 were found to be top rankers for grain yield per plant in comparison to the better check, SHM-2. The analysis of variance for combining ability, in both the normal and heat stress conditions, revealed highly significant mean squares due to general combining ability(GCA), specific combining ability (SCA) and reciprocal combining ability (RSCA) for all the characters studied except due to reciprocal combining ability for anthesis-silking interval in normal condition. The pooled analysis of variance revealed significant mean squares due to general combining ability, specific combining ability, reciprocal combining ability, environments, GCA x environments, SCA x environments, reciprocal x environment for all the characters studied, except due to GCA x environments for anthesis-silking interval and due to reciprocal x environment for 500-seed weight. Estimates of components of variance for thirteen characters revealed that variance due to SCA was more than variance due to GCA and reciprocal for all the characters studied in both the conditions. The pooled analysis revealed that variance due to GCA was more than variance due to SCA and reciprocal for the characters viz., days to 50% silk, pollen viability, anthesis-silking interval, cell membrane thermo stability, days to 50 per cent physiological maturity, grain filling period, grains per plant, 500-seed weight and shelling percentage. Variance due to SCA was more than variance due to GCA and reciprocal for the characters, namely, days to 50 % anthesis, plant height, ear height, grain yield per plant. Parents CML 411 was found to be good general combiner for grain yield per plant in both the normal and heat stress conditions and in pooled analysis, whereas, CML 306, CML 164, CML 307 were considered as good general combiners in heat stress condition, while CML 164 and CML 304 were found to be average general combiners in normal condition and pooled analysis. Similarly, CML 306 and CML 307 were found to be average general combiners in pooled analysis for grain yield. In normal condition, crosses, namely, P1 x P4, P2 x P3, P1 x P2, P6 x P7 and P5 x P7; in heat stress, crosses, namely, P2 x P7, P1 x P7, P4 x P6, P3 x P6 and P1 x P4 ; and In pooled analysis crosses, namely, P1 x P4, P2 x P7, P2 x P3, P5 x P7 and P1 x P7 were found to be top five good specific combinations for grain yield per plant. Reciprocal specific combinations, in normal condition, crosses, namely, P4 x P1, P3 x
P2 and P6 x P2; in heat stress condition, crosses, namely, P4 x P1, P4 x P2, P6 x P2, and P5 x P4 ; and in pooled analysis, crosses, namely, P4 x P1 and P3 x P2 were found to be top combinations good for grain yield per plant. Standard heterotic combinations, in normal condition, crosses namely, P2 x P3 and P1 x P2; and in heat stress condition and in pooled analysis, cross P2 x P7 were found to be significantly top two for grain yield per plant. The best experimental hybrid was identified on the basis of SCA/RSCA, GCA, mean performance and standard heterosis for grain yield in different situations. The experimental hybrid, CML 411 x CML 305 was identified as the promising hybrids for normal condition, whereas, the experimental hybrid, CML 411 x CML 307 was identified for heat stress condition and the experimental hybrid CML 411 x CML 307 was identified as the promising hybrids over the environment.