Breeding Investigations in Single and Double Cross F4 and F5 Populations of Bhendi [Abelmoschus esculentus (L.) Moench]  

Prakash Gangashetty1 , Laxman Malakannavar2 , Satish Adiger1
1. Department of Genetics and Plant Breeding, College of Agriculture, UAS Dharwad-580005, India
2. Department of Genetics and Plant Breeding, College of Agriculture, GKVK, UAS Bengaluru, India
Author    Correspondence author
Molecular Plant Breeding, 2013, Vol. 4, No. 12   doi: 10.5376/mpb.2013.04.0012
Received: 25 Mar., 2013    Accepted: 27 Mar., 2013    Published: 30 Mar., 2013
© 2013 BioPublisher Publishing Platform
This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Prakash et al., 2013, Breeding Investigations in Single and Double Cross F4 and F5 Populations of Bhendi [Abelmoschus esculentus (L.) Moench], Molecular Plant Breeding, Vol.4, No.12 96-106 (doi: 10.5376/mpb.2013.04.0012)

Abstract

A study was conducted to assess the genetic variability, correlation and path analysis in four single cross and three double cross F4 and F5 populations of bhendi. The study indicated that double cross populations have reported higher magnitude of variability compared to single cross populations. High variability was observed for number of fruits per plant, plant height, internodal length, fruit weight and fruit yield per plant. Moderate variability for fruit length and fruit diameter and low variability for days to first flowering, days to 50% flowering, number of seeds per fruit and 100-seed weight. Phenotypic correlation revealed high positive correlation of fruit yield per plant with number of fruits per plant, number of branches per plant, plant height, fruit weight, fruit length and 100-seed weight. Path analysis depicted high effect on number of fruits per plant, fruit weight, plant height and number of branches per plant with fruit yield per plant. To release importance of fruit yield, direct selection can be practiced for these characters.

Keywords
Bhendi; Single cross; Double cross; Populations

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.

Results and Discussion
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

The magnitude of heritability ranged from 59
% (number of fruits per plant in double cross progeny) to 99% (plant height). More than 70% heritability recorded for days to first flowering, days to 50% flowering, plant height, inter nodal length, number of branches per plant, fruit weight, fruit diameter, 100 seed weight, number of seeds per fruit in both single and double cross populations. High heritability suggested the major role of genetic constitution in the expression of the character and such traits are considered to be dependence for genetic up gradation of bhendi. The estimates of heritability along with genetic advance were more reliable than heritability alone for predicting the effect of selection.The value of GAM ranged from 3.31% (days to first flowering) to 53.58% (number of branches per plant in single cross) and from 3.63% (days to first flowering) to 43.84% (number of branches per plant in double cross). High heritability coupled with genetic advance over mean in number of branches per plant, inter nodal length, fruit weight, number of fruits per plant; and fruit yield per plant in both single and double cross indicated that these characters had additive gene effect and therefore they are more reliable for effective selection. High to moderate heritability coupled with moderate to low GAM for days to first flowering, days to 50% flowering, plant height, number of seeds per fruit. These findings are in agreement with the earlier reports of Panda and Singh (1997), Singh et al(1998), Dhall et al (2001) and Dhankar and Dhankar (2002).
In bhendi fruit yield is dependent character and highly influenced by environment, so far the improvement of yield components, knowledge of their association with its main component is beneficial in formulating the breeding programme. Positive and significant phenotypic association of plant height, number of branches per plant, fruit weight, fruit length, 100 seed weight and number of fruits per plant with fruit yield per plant indicted that effective improvement in yield through these characters could be achieved. Similar findings in bhendi have been reported by Singh et al, and Dhankhar and Dhankhar (2002). However phenotypic correlation between fruit yield per plant and days to first flowering, inter nodal length and fruit diameter was significant negative indicating that this character shall have least significance for improving fruit yield in okra. Similar results were reported by Singh et al (1998), Dhankar and Dhankar, 2002), Jaiprakashnarayan and Mulge (2004) and Sarkar et al (2004). The results suggest that such type of negative correlation among components will not be helpful for selection of particular character as they shall adversely effect on other traits
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 a
l (1976) in okra.
Lush (1940) defined heritability in broad and narrow sense and emphasized that characters are subjected to different amount of non heritable variation. The broad sense heritability includes genotypic variance and phenotypic variance, but genotype variance includes both dominance and additive variance, so it is not a reliable index for practicing selections. While narrow sense heritability includes additive variance and phenotypic variance, so additive variance is a reliable index of the total genotypic variance, and selections will be effective for carry forwarding the lines or genotypes to next generation.
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.
Material and methods
The experimental material in the present study consisted of F4 and F5 populations of four single crosses (BH-10, BH-11, BH-13 and BH-14) and three double crosses (BH-15, BH-16 and BH-16) along with popular checks. The experiment was laid out in RBD with three replications during summer 2008 (F4) and kharif 2008 (F5) at Agricultural Research Station, Hanumanamatti, University of Agricultural Sciences, Dharwad. Each progeny line was sown at a spacing of 60 cm´30 cm with a round length of 5 m having eight progeny lines in each single cross and 10 progeny lines in each double cross in both the generations. All the recommended agronomic package of practices was followed to raise good healthy crop. The observations were recorded from five competitive plants from each row (totally 40 plants in each single cross and 50 plants in each double cross) on twelve quantitative characters viz., days to first flowering, days to 50 per cent flowering, plant height (cm), number of branches per plant, internodal length (cm), fruit weight (g), fruit length (cm), fruit diameter (cm), number of seeds per fruit, 100-seed weight (g), number of fruits per plant, fruit yield per plant (g). The genotypic and phenotypic coefficients of variability were calculated according to the method suggested by Burton (1952). Heritability in broad sense were calculated as per Hanson et al(1956) and genetic advance according to Johanson et al(1955). Correlation was worked out according to the formula given by Weber and Moorthy (1952). Direct and indirect effects were worked out as per Dewey and Lu (1959). Inter generation correlation coefficient for all the twelve quantitative characters between F4 and F5 generations were calculated as per Weber and Moorthy (1952). Narrow sense heritability was calculated as per Cahaner and Hillet (1980) based as parent offsprings regression method.
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