Genetic maps are a vital tool in cultivar improvement programmes for woody perennial tree crops such as tea (Camellia sinensis). A population thought to be derived from two known, noninbred parents was scored for RAPD and AFLP markers, in order to develop a linkage map. However, a very high proportion of the markers exhibited unexpected segregation ratios in the light of their con®gurations in the parents, and an exploratory statistical analysis revealed patterns in the marker scores which can most easily be explained by the hypothesis of three male parents contributing pollen to this cross. We discuss the evidence for this and the subsequent analysis required to assemble the markers from the female parent into the ®rst linkage map for tea. The map has 15 linkage groups of three or more markers, agreeing with the haploid chromosome number of tea. The statistical methods that revealed the subpopulations are easy to apply routinely, and may prove a useful diagnostic tool for the analysis of noninbred mapping populations.
An experiment was conducted to study the nature and magnitude of genetic variability with a view to identify promising genotypes for yield and related traits in linseed. Eighteen diverse linseed (Linum usitatissimum L.) genotypes were evaluated in randomized block design in three replications during rabi 2019-20 for twelve agro morphological characters to assess the genetic parameters of variability. Analysis of variance indicated presence of a wide range of genetic variability among genotypes for all the traits. The higher phenotypic coefficient values than corresponding genotypic coefficient values depicted influence of environment in the expression of traits. Technical height exhibited highest GCV value while the lowest GCV was observed for days to 75% maturity. High estimates of PCV and GCV indicate sufficient variability, signifying the effectiveness of the selection of desirable types for improvement of such characters. The high expected genetic advance expressed as percentage of mean were recorded for technical height, aerial biomass per plant, plant height, primary branches per plant and secondary branches per plant. High heritability with moderate genetic advance was observed for technical height indicating the presence of additive and non-additive gene action. Path analysis revealed, direct and indirect effects of genotypic path coefficient were higher in magnitude than the corresponding phenotypic path coefficients. Highest positive direct effect on seed yield was shown harvest index followed by aerial biomass, plant height, secondary branches per plant and days to 75% maturity. The obtained results could be used further in breeding programmes.
Present study comprises of 45 introduced and 2 indigenous genotypes of linseed which were evaluated at Experimental Farm of the Department of Crop Improvement, CSK HPKV, Palampur during rabi 2018-19. The experiment was carried out in RCBD with three replications. Each genotype was evaluated for 10 yield contributing characters. High heritability coupled with high genetic advance was recorded for primary branches, secondary branches, number of capsules, biological yield and seed yield. Seed yield showed highest significant positive correlation with biological yield (0.847) followed by plant height, primary branches and secondary branches. Significant negative correlation was observed for days to 50 per cent flowering and days to 75 per cent maturity. The results of path analysis revealed highest direct effect of biological yield (1.088) and harvest index (0.554) with seed yield, while primary branches, secondary branches and number of capsules showed higher indirect effects via biological yield.
Stability performance of 30 linseed genotypes including commercial cultivars and elite lines (indigenous and exotic) was compared by using regression on environmental means for grain yield and its components under 5 different environments during rabi 2013-2014. Significant differences were observed among the genotypes for all the traits studied over all 5 individual environments. Genotype × environment interactions were highly significant for all the characters studied. E + (G × E) was significant for all the characters except the number of seeds per capsule. Mean sum of squares for environment (linear) showed significance for all the characters. Significant differences for G × E (linear) were observed for 5 traits viz., primary branches per plant, secondary branches per plant, aerial biomass yield per plant, seed yield per plant and 1000-seed weight. Based on mean performance, regression coefficient (bi) and deviation from regression (S2di) the genotype Him Alsi-2, KL-241 and Nagarkot was highly stable for seed yield (g) and number of capsules per plant was found most adaptive to overall environments. These promising genotypes may be utilized as donors in linseed improvement program for target ecosystems.
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