Bhendi [Abelmoschus esculentus (L.) Moench] also known as ladies finger is an important vegetable crop cultivated throughout the world and is a native of tropical Africa. India is the largest producer of okra covering an area of 3.91 lakh ha with an annual production of 39.7 lakh tonnes. It has good nutria- tional value, particularly vitamin C (30 mg/100 g), calcium (90 mg/100 g) and iron (1.5 mg/100 g) in the edible fruit. It is a potential exporter earner accounting for 13% of export of fresh vegetables. All forms of plant improvement activities through breeding contemplate an eventual boost in genetic potential for yield. Since, yield is polygenically controlled and highly influenced by environment, selection based on yield alone is not effective. The breeder hence develops into proposition of selecting for high yield indirectly through yield associated and highly heritable characters after eliminating environmental components of phenotypic variance. An attempt to improve a character by selection would be futile unless a major portion of variation is heritable which depends entirely on the magnitude of genetic variability in the source progeny. The variability generated is a pre-requisite for any breeding programme aimed at improving the yield and other characters. Thus, it is imperative to have information on both genotypic and phenotypic coefficients of variation together heritability and GAM will be handy for prediction of the possible genetic advance by selection for the character. Besides, the knowledge of correlation and path coefficient analysis would assist in setting up selection indices. The genetic parameter such as genotypic coefficient of variation and genetic advance helps to split the total variability into heritable and non-heritable components. Therefore, the present investigation has been undertaken to compare the variability in single and double cross F₄ and F₅ populations of bhendi.

The genotypic and phenotypic coefficient of variability, heritability and genetic advance, character-wise are presented in Table 1. The magnitude of phenotypic coefficient of variation (PCV) was higher than the corresponding genotypic coefficient of variation (GCV) for all characters under study. Higher magnitude of GCV and PCV were recorded for number of branches per plant and number of fruits per plant in both single and double cross F₄ populations. This reflects greater genetic variability among genotypes for these characters and is desirable for further improvement by selection. However moderate to low GCV and PCV were recorded for days to first flowering, days to 50% flowering, inter nodal length, fruit weight, fruit length, fruit diameter, number of seeds per fruit and 100 seed weight (Table 1). Panda and Singh (1997) obtained similar results with okra hybrids and Singh et al (1998) reported parallel results while evaluating different induced mutants in okra. Most of the characters in double cross F₄ populations revealed presence of high magnitude of genetic variability. Low GCV and PCV for most of the characters in single cross revealed that genetic variability in single cross populations compare to double cross populations.

Table 1 Comparison of variability between single cross and double cross F4 and F5 populations for twelve quantitative characters

It is apparent that many of the characters are correlated because of mutual association, positive or negative with fruit yield and its contributing characters. As more variables are considered in correlation with table, indirect association becomes complex, less obvious and somewhat perplexing. At this point, path coefficient analysis provides an effective means of separating direct and indirect causes of association. The persual of path coefficient analysis (Table 2~Table 5) revealed that number of fruits per plant showed maximum direct effect on fruit yield per plant followed by average fruit weight, number of branches per plant. However internodal length, days to 50% flowering had negative direct effect on fruit yield per plant. High direct effect of number of fruits per plant, number of branches per planti and fruit weight on fruit yield per plant were earlier reported by Jaiprakashnarayan and Mulge (2004) and Sarkar et al(2004).The characters which showed maximum direct effect should be considered in selection programme for improving fruit yield per plant. Indirect effects towards fruit yield per plant through various characters suggested that for selecting genotypes with higher fruit yield the indirect influence of different traits should be given due weightage along with characters which exerted direct effects to break yield pattern. From the present study on the basis of variability and character association, it could be concluded that generally double cross populations exhibited higher magnitude of genetic variability compare to single cross populations. For making selections in these populations on the basis of number of fruits per plant, number of branches per plant, plant height and fruit weight which exhibited appreciable direct effects on fruit yield per plant proved as important component of yield and the selection based on these characters would lead to development of high yielding genotypes of bhendi. In crop like bhendi rapid increase in fruit yield was achieved by early and advanced generation selection.

Table 2 Phenotypic correlation coefficients for twelve quantitative characters in single and double cross F4 populations

Table 3 Phenotypic correlation coefficients for twelve quantitative characters in single and double cross F5 populations

Table 4 Path coefficient analysis of fruit yield per plant versus yield components in F4 populations of single and double cross

Table 5 Path coefficient analysis of fruit yield per plant versus yield components in F5 populations of single cross

Intergeneration correlation coefficients give an idea about the effectiveness of single plant selection and to some extent on nature of gene action (Table 6). If the correlation coefficient is high, it would mean high heritable portion and probably the additive component. In the present study, high heritability and significant correlation were observed for internodal length, number of seeds per fruit and 100 seed weight in both single and double cross populations. Indicating these traits are mostly governed by additive gene action and suitability of these traits for selection on individual plant basis in the advanced generations of segregating populations. These findings were supported by Kulkarni et al (1976) and Reddy et al(1985).

Table 6 Intergeneration correlation coefficients between F4 and F5 generation for twelve quantitative characters

The Plant height, number of branches per plant, fruit weight, number of fruits per plant and fruit yield per plant were recorded low values of correlation coefficient and heritability indicates non correspondence of two generation values for these characters and which could be attributed to preponderance of non additive variation. If additive variance will be present for a trait, then selection for such traits will be effective. Which would further helps in developing inbreeds or varieties. If dominance variance is present, then it is going to reduce and gradually disappear in future generations. For such traits one need to go for heterosis breeding to develop hybrids. These reports are in accordance with Kulkarni  et al (1976) in okra.

The high narrow sense heritability was observed for days to 50 per cent flowering, internodal length, number of seeds per fruit and 100 seed weight, indicate these characters were governed by additive variance. So selection will be effective for such traits based on phenotypic observations (Table 7).

Table 7 Heritability (Narrow sense) estimates for twelve quantitative characters in single and double cross populations

Low to moderate narrow sense heritability was observed for number of branches per plant, fruit weight, fruit length and number of fruits per plant. This indicates both dominance and additive variance (epistasis) for these traits. So, selection based on phenotypic observations may not be effective. Under such situation, the progeny test will be required to confirm the worth of genotypes.

Singh A.K., Singh K.P., and Singh V.P., 1998, Genetic analysis of induced mutants of okra (Abelmoschus esculentus (L.) Moench), Veg. Sci.,25(2): 174-181