Study of Inheritance Pattern and Selection Index in Chickpea (Cicer Arietinum L.)

Abstract

The whole work of the present investigation was carried out under three separate heads, such as part-I consist study of variability, heritability, genetic advance, correlation coefficient, path coefficient and selection index; part-II consist genotype × environment interaction and part-III consist genetic study. Again, part-III i.e. genetic study had been done following three biometrical model viz., genetic study-1 deals with generation mean analysis, genetic study-2 deals with biparental progeny (BIPs) analysis and genetic study-3 deals with triple test cross (TTC) analysis. The thirteen yield and yield contributing characters viz., date of first flower (DFF), plant height at first flower (PHFF), number of primary branches at first flower (NPBFF), number of secondary branches at first flower (NSBFF), date of maximum flower (DMF), plant height at maximum flower (PHMF), number of primary branches at maximum flower (NPBMF), number of secondary branches at maximum flower (NSBMF), plant weight at harvest (PWH), number of pods per plant (NPd/P), pod weight per plant (PdW/P), number of seeds per plant (NS/P) and seed weight per plant (SW/P) of eight chickpea genotypes were taken for the analysis. The experiment was set up during the four consecutive robi seasons of 2009-2010, 2010-2011, 2011-2012 and 2012-2013 at the Botanical Research Field, University of Rajshahi, Rajshahi-6205, Bangladesh. In part-I, the analysis of variance showed significant differences among the genotypes for all the thirteen studied characters. The phenotypic variation (σ2 p) was greater than those of other components of variation for all the characters. The highest phenotypic variation was observed for NPd/P followed by NS/P and PWH. It is also noticed that phenotypic coefficient of variability (PCV) in general, was higher than the estimates of genotypic coefficient of variability (GCV) for all the characters. The highest GCV with high PCV were found for NS/P and NPd/P. The heritability (h2 b), genetic advance (GA) and genetic advance as percentage of mean (GA %) were found to be low for most of the characters. Regarding correlation coefficient, the most important trait SW/P that is yield per plant exhibited positive association with NPBFF, NPBMF, NPd/P, PdW/P and NS/P both at genotypic and phenotypic levels. The path coefficient analysis had been done based on SW/P as a dependent variable revealed that NS/P had the highest positive direct effect on seed weight, both at genotypic and phenotypic levels. On the other hand, the highest negative direct effect on SW/P was recorded for NPd/P both at genotypic and phenotypic levels but highest positive indirect effect of NS/P nullified its negative effect and finally it turn into positive. In the analysis of descriminant function, it showed that the combination of two attributes viz., NPBFF and NPBMF gave the highest expected genetic gain. Since these two traits exhibited highest genetic gain in the combination of selection index and showed positive correlation with SW/P both at genotypic and phenotypic levels hence considered as primary yield component. However during selection study emphasis may be given on PdW/P and NS/P as they showed high correlation and positive direct effect on seed yield. Considering heritability, genetic advance and positive association with SW/P, trait NPd/P should also be given importance during selection of chickpea trait. In part-II, genotype × environment (G×E) interaction was carried out according to Freeman and Perkins (1971) model. The results of joint regression analysis exhibited that the mean square due to genotypes were significant for all the traits. All the studied traits except DMF exhibited significant variation due to environmental changes. Combined regression displayed significant values for PHFF, NPBFF, NSBFF, DMF, NPBMF, NPd/P, PdW/P and NS/P in comparison to residual-1. Resedual-1 item in comparison to error was significant for the traits DFF, NSBFF, PHMF and SW/P. According to Freeman and Perkins (1971) model a desired genotype should be with high mean performance, a nearly unit regression coefficient (bi=1.0) and non-significant deviation from regression ( di S2 ) irrespective of sign. On the basis of the above mentioned criteria the genotype-1 for DFF, NPBFF and DMF; genotype-2 for NSBFF and NPBMF; genotype-3 for NSBFF; genotype-4 for NSBMF; genotype-5 for NPBFF and NPBMF; genotype-6 for NSBMF and SW/P and genotype-7 for NPBFF and NPBMF were considered as stable genotypes. On the other hand, genotype-1 for PHFF and PHMF; genotype-2 for PHMF, NSBMF and SW/P; genotype-3 for DFF, NPBFF, DMF and PHMF; genotype-5 for NSBFF; genotype-6 for DMF, NPBMF and PdW/P and genotype-7 for DMF, NSBMF and SW/P were considered as suitable genotypes for favorable environments. For the genetic study of chickpea, five different crosses were considered in part-III. Obtained results of genetic study-1 in part-III that is generation mean analysis is performed by Mather’s (1949a) scaling test. In this case, scales (C and D) showed significant for most of the characters and crosses. C and D were found to be non-significant for PWH in cross-2; for NSBFF, PHMF and NSBMF in cross-3 and for NPBMF in cross-4 indicated additive-dominance model was adequate for these traits. On the other hand, Cavalli’s (1952) joint scaling test showed significant χ2 values in maximum cases. Non-significant χ2 values observed for PWH, NPd/P and NS/P in cross-2; for NSBFF and NSBMF in cross-3 and for NPBMF in cross-4. In the present investigation, dominance effect [h] plays a greater role in the inheritance of most of the traits due to their higher magnitude than additive effect [d]. The negative sign of [h] indicated dominance towards decreasing parent. In the present study, most of the characters exhibited duplicate type epistasis. The character PWH in cross-5 exhibited complimentary type of epistasis. Complementary gene action could be successfully exploited in the selection programme. The values of degree of dominance (√H/D) for most of the characters in studied crosses showed over dominance. The number of effective factor i.e. K1 was found less than one for all the characters and crosses. Heritability estimates both in broad (h2 b) and narrow (h2 n) senses were found to be high in majority cases. Both the high values of broad and narrow sense genetic advance (GA) as well as genetic advance as percentage of mean (GA%) indicated that improvement of these characters is possible through selection. The values of mid-parents (MP) heterosis were non-significant for most of the characters in studied crosses. Results obtained from the genetic study-2 that is biparental progeny (BIPs) analysis, showed significant difference among the families (crosses) for all the characters except DMF in cross-1; NSBFF and NPd/P in cross-4 and DMF, NPBMF, NPd/P, PdW/P and SW/P in cross-5 which suggests considerable variation among the BIPs families. In the present investigation, magnitude of additive (DR) component was higher than that of dominance (HR) component for NPBMF, NSBMF and PdW/P in cross-1; for DFF, NSBFF, DMF, PHMF, NPBMF and NSBMF in cross-2; for NPBFF, NPBMF, PdW/P, NS/P and SW/P in cross-3; for DMF, NPBMF, NPd/P, PdW/P, NS/P and SW/P in cross-4 and for DFF, PHMF, PdW/P, NS/P and SW/P in cross-5. This result indicated the relative important of additive gene action in the inheritance of these characters. Therefore, selection for these traits which exhibited additive gene action will be very effective. Over dominance for most of the characters and crosses were noted in the present study. The significant regression item in some cases revealed good relationship between biparental progenies and their parents. Both broad and narrow sense heritability and genetic advance (GA) were low for most of the traits in each cross. In case of NPBFF, DMF, PWH, NS/P and SW/P in cross-1; PHFF, PWH, NPd/P, NS/P and SW/P in cross-2; PHFF, NSBFF and PWH in cross-3; NSBFF, NSBMF, NPd/P and PdW/P in cross-4 and DFF, NSBFF, NPBMF, NSBMF and NPd/P in cross-5, both heritability and genetic advance in narrow sense were higher than broad sense heritability and genetic advance. This indicated that additive gene action was important in the expression of these traits. Thus additive gene action is a measure of breeding value of a genotype. Hence, for these traits which showed preponderance of additive gene action, reliance should be placed on pure line selection, mass selection and or progeny selection. By comparing total variances of F2 BIPs, F2 and F2×F1 generations, it found that the linkage was present in repulsion phage for most of the characters. Again, in the genetic study-3 that is triple test cross (TTC) analysis; total epistatic effects were found to be non-significant for all the studied traits. But partitioning of total epistasis indicated the involvement of ‘i’ type (additive × additive) epistasis for DFF, PHFF, PWH, NPd/P, PdW/P, NS/P and SW/P in cross-1; NPBFF and NSBFF in cross-3 and for PHFF, DMF, PHMF and NSBMF in cross-5 and involvement of ‘j+l’ type epistasis for DFF in cross-2; for PHMF, NSBMF and NS/P in cross-3 and for PHFF and NSBFF in cross-4. The magnitude of additive component was higher than that of dominance component for most of the traits. Incomplete dominance was noted for most of the traits in each cross which indicated that the predominant nature of additive genetic component. Both broad sense and narrow sense heritability estimates were found to be moderately high or high for most of the characters. Positive and significant correlation between sums and differences found for NSBFF, PHMF, NPd/P, PdW/P, NS/P and SW/P in cross-1; for DFF and NSBMF in cross-3 and for DFF and NPBMF in cross-5 indicated that direction of dominance towards decreasing parents while, negative and significant correlation between sums and differences observed for DMF in cross-1; for NPd/P, PdW/P, NS/P and SW/P in cross-2; for PHMF in cross-3 and for DFF in cross-4 indicated the direction of dominance towards increasing parents.