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Genetic Studies in Environments Lablab Bean Under Two Cultural Environments

S. N. Begum
Scientific Officer
Plant Breeding Division, BINA, Mymensingh

M. A. Newaz
Department of Genetics and Plant Breeding, Bangladesh Agricultural University, Mymensingh

Abstract/ Executive Summary:

Results on inheritance study, which was investigated in a single cross (KBS1 X DS167) comprising parental, F₁, F₂ and F₃ populations under two cultural environments, showed populations in Env. 1, with Partly sowing date, required more time to flower than in Env. 2, with late sowing. Env. 1 gave more pod yield/plant than Env. 2, which was 'mostly achieved through higher number of inflorescence/plant that bore edible pods. Scaling tests yielded differential results as to the adequacy of simple additive-dominance genetic model for different characters in two environments. Presence of non-allelic interaction in the genetic system of inflorescence/ plant was strongly indicated by all the scales in both the environments. High broad heritability (h²b%) with moderate expected genetic advance (GA%) were observed for some characters including days to flowering, pods/inflorescence, pod length and 10-pod weight in both environments. Generally, the estimates of h² b (%) and GA (%) were relatively higher with late sowing (Env. 2) than with early sowing (Env. 1) for majority of the characters; notable exceptions being number of inflorescence and pod yield per plant in which cases the reverse was true.

Keywords: Genetic studies, Environment, Lablab bean

Location: Mymensingh

Start Date: 20-08-1996

End Date: 30-03-1997

Program Area: Variety and Species

Commodity: Lablab bean

Objectives:

To gather information on the mode of inheritance, heritability and related genetic aspects under two cultural environments in a cross of lablab bean covering several filial generations.

Methodology:

Experimental materials included two parental genotypes, with BAU accession KBS1 and DS167, and their three filial generations viz. F₁ , F₂ and F₃KB81 is a selected breeding line of early flowering, isolated at BAU, from a cross between a local and a Japanese genotype (D821/B X D8109); and D8167 is also a Japanese genotype, with short plant type and early flowering behaviour. The experiment was grown in a RCB design with five replicates during August 1996- March 1997 at the experimental farm of Department of Genetics and Plant Breeding, Bangladesh Agricultural University, Mymensingh. Two cultural environments, designated as Env. 1 and Env. 2, were created by differential sowing dates; Env. 1 with early sowing date (20 Aug./96} and Env. 2 with late sowing (20 Sept./96). Pits were spaced 2m both between rows and within rows. Data were recorded on days to flowering, no. of inflorescences/plant, pods/inflorescence, pod length (em), pod width (em), seeds/pod, 10-pod weight (g) and green pod yield (kg). In all ten plants for each of KBS1 (P ₁), D8167 (P₂), and F₁ , 40 plants for F₂ and 35 plants for F₃ were used for data recording. Scales were tested by using the formula suggested by Mather and Jinks (1977) and Singh and Chaudhary (1979}. Genotypic and phenotypic coefficients of variation (GCV and PCV) were worked out following the formula given •by Burton (1952). Heritability in broad sense was estimated using the formula suggested by Johnson et a/. (1955) and Hanson et a/. (1956) and genetic advance was calculated according to the formula given by Allard (1960). Genetic advance in percentage of mean was calculated as proposed by Comestock and Robinson (1952}.

Source of Information: Bangladesh J. Agril. Sci. 27(2): 185-189, July, 2000

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Environmental variance was higher than the genotypic variance in Env. 1 indicating vulnerability of inflorescence/plant to the environmental influences. Difference between GCV and PCV was comparatively low for days to flowering, pods/inflorescence, pod width and 10 pod weight in Env. 1 and days to flowering, inflorescence/plant, pods/inflorescence, pod length, 10-pod weight and yield/plant in Env. 2 which indicated that the major portion of the phenotypic variance was genetic in nature. In Env. 1 the genotypic and phenotypic variances for pod width were low whereas genotypic and phenotypic coefficients of variation were high. Moderate values of heritability and lower values of GCV and Ga were estimated for seeds/ pod, indicating limited scope for improvement in this character. In both environments, maximum phenotypic and genotypic variances were found for 10-pod weight, which indicated greater scope for selection and improvement for this trait. In pod yield/plant, the PCV was higher than the GCV in Env. 1 which suggested that the environmental effect contributed more to PCV. However, because of lower value of GCV as compared to PCV, selection in this trait may not be effective. In Env. 2, unlike Env. 1, the estimates of PCV and GCV in this trait were very close indicating that genotypic contribution was greater. This aspect of results in two environments was thus contradictory to each other. Heritability, estimated in broadsense, was reasonably high and genetic advance moderate for several traits such as days to flowering, pods/inflorescence, pod length and 10-pod weight regardless of environments; but then importance of non additive components and departure from simple additive-dominance genetic model was clearly demonstrated by scaling test in many cases especially number of inflorescences/plant. Moderate heritability with moderate GA (%) in Env. 1 and Env. 2, respectively. Moderate heritability with low GA (%) was observed for seeds/pod in both environments, indicating limited scope for the improvement of this character. Pod yield/plant had high heritability with high genetic advance in Env. 2 but Env. 1 showed moderate heritability with moderate genetic advance (%).The results obtained in the present study points to the need of carrying such genetic studies in differential environments rather than singular one for a more genuine and valid conclusion.

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