A broad based wheat germplasm consisting of 150 genotypes was evaluated at five locations representing various agro-ecological zones of the country to select diverse parents for hybridization to investigate gene-action on the basis of diallel technique and scaling test. Five diverse genotypes C-591, Rawal-87, V-8203, CB-51 and V-90R-34 were selected as parents to be used in hybridization programme. The genotype CB-51 was a late maturing variety, whereas Blue Silver matured early. All the selected genotypes were genetically diverse and had specific plant traits.
High genetic variation was observed for all the five locations indicating the worth of material evaluated. Elite lines for specific traits were identified for future exploitation in the breeding programme. Genetic dissimilarities based on Wardâ€™s methods for five locations revealed seven clusters. Clusters I, III and V comprised of 22 genotypes. Maximum genotypes (26) were found in cluster IV. Cluster VI consisted of 14 genotypes and cluster 11 19 genotypes. Six genotypes (C591, Blue Silver, Rawal-87, V-8203, V-90R-34 and CB-51) were selected as parents for further study of gene action. All the parents were observed in different clusters representing maximum genetic diversity to be incorporated for gene recombination.
Six parents along with other four genotypes (Chenab-70, Oligo culm # 380, Janz and Fukuho kumugi) were evaluated for RAPD using 32 primers. Genotype specific bands were observed for individual primers and in combination of various primers that could help in resolving genetic diversity and linkage with other characters. Based on 200 RAPD markers, four groups were observed and clustering was on the basis of plant characters along with drought status of the parents. In total, 422 RAPD fragments were recorded and analyzed for genetic linkage that revealed three varieties (Oligo-culm # 380, Janz and Fukuho-kumugi) were in same group, V -8203 in second group, four (CB-51, Chenab-70, 90R- 34, Blue Silver) in third group and two (Rawal-87 and C 591) in the forth group. Random amplified polymorphic dna technology was considered a useful tool to detect genetic variation at the DNA level and tagging genotypes for specific traits.
The research material comprising of six parents, 30 progenies each of F1, F2 , BC1 and BC2 was evaluated in a compact family block design to study the genetic architecture of quantitative characters. Significant differences were observed for all the characters, except spike length. The progenies exhibited significance for all the characters under study that indicated the genetic divergence of the parents used in the breeding programme. Combining ability analysis CGCA) revealed significance for all the characters in F1 and F2 generations except spikelets per spike and spike density in F1 General combining ability variance was greater than specific combining ability in both F1 and F2 generations for all the characters, except number of spikelets per spike and spike density in F1 generation. This indicated the presence of additive genetic variance for all the characters except for spikelets per spike and spike density, where dominance or epistatic type of gene action was observed. The reciprocal crosses in most of cases did not give similar performance for various parameters which indicated the influence of maternal contribution, hence the hybrids were suggested to be evaluated separately in advance generations.
The parent Rawal-87 was the best general combiner for narrow flag leaf area, early heading, short duration, higher plant height at booing stage, tillers per plant, spikelets per spike, grain per spike, 1000 grain weight, biological yield and grain yield. Parent V -8203 was found the best general combiner for harvest index, days to heading, spike length, grains per spike and grain yield. Variety C591 showed the best general combining ability effects for plant height at booting stage, plant height at maturity, tillers per plant and good for harvest index in both F1 and F2 generations. The hybrids of the best parents were suggested to be evaluated carefully for identifying transgressive segregants in future generations.
On the basis of genetic information, epistasis has predominant role in the expression of all the characters for all 30 hybrids, except V -90R-34/Rawal-87 for flag leaf area, Blue Silver/V -90R-34 and Rawal-87 IV -8203 for days to heading, Blue Silver/Rawal-87 and Blue SilverN-90R-34 for days to maturity, Rawal-87/V-90R-34 and CB-51/Blue Silver for tillers per plant, Rawal-87 /CB-51, V -8203/Rawal-87, V -8203/V-90R-34, V-8203/CB-51 and CB-51/C591 for spikelets per spike and V-8203/C59L V-90R-34/Rawal-87 and V-90R34/V-8203 for harvest index. Allelic interaction was observed in all the 30 hybrids except, C591/Blue Silver and CB-5/1V -90R-34 for spike density and C591/Rawal-87, C5911CB-51, Blue Silver/C591, Blue Silver/Rawal-87, Blue Silver/CB-51, Rawal-87/V -8203, Rawal-87/CB-51, V -8203/ C591, V -8203/V -90R-34, V -8203/CB-51, V -90R-34/C59I and CB-51 /Rawal-87 for spike length.
It was observed that selection in early generation could be more effective in cross Blue Silver/CB-51 for yield components viz., spikelets per spike, spike length. grains per spike, bold grain, higher biological yield, grain yield per plant and harvest index. hence careful selection is needed from F2 or F3 to identify the best recombinants. Similarly the cross Blue Silver/V -90R-34 was expected to produce better segregants for narrow flag leaf area, higher plant height at booting stage, short stature at maturity. greater spikelets per spike. grains per spike, bold grain, biological and grain yield per plant and harvest index in early generations.
The crosses, C59/V-8203, C59/V-90R-34 and V-90R-34/Rawal-87 were expected to produce better segregants for most of the plant characters like flag leaf area. early heading and early maturity, higher plant height at booting stage, short stature at maturity, more tillers per plant, more grains per spike, higher biological and grain yield per plant. Additive effects [D] of genes were significant for all the traits except spikelets per spike, biological yield and grain yield per plant in F1 and F2. Dominance gene effects [H1] were significant for flag leaf area, days to heading, days to maturity, plant height at booting stage, spikelets per spike, grains per spike, spike length, spike density, 1000 grain weight and harvest index in F1 generation. Whereas, in F1 eight traits [flag leaf area, plant height at booting stage, plant height at maturity. tillers per plant, grains per spike, 1000 grain weight, biological yield per plant and grain yield per plant] showed non-significant dominance gene effects.
Recessive alleles were predominant for flag leaf area, days to heading, plant height at booting stage, tillers per plant. spikelets per spike, grains per spike, spike length. biological yield and grain yield per plant. Over-dominance inheritance was expected for days to maturity and 1000 grain weight in F1 and spikelets per spike, spike length and biological yield in F2. Comparison of narrow sense heritability in F1 and F2 generations for quantitative traits revealed linear relationship that indicated the importance of genetic variances in both the generations.