Abstract: The objective of this study was to assess eighteen accessions of Solanum anguivi collected from various diverse sources for broad-sense heritability, genetic advance and character of association in yield related traits. The experiment was laid out in a Randomized Complete Block Design (RCBD) with four replications. High estimates of broad sense heritability was observed in plant height at maturity (76.67), number of branches per plant (83.9), total number of fruits per plant (85.5), total weight of fruits per plant (86.96) suggesting additive gene effect in these characters. Number of branches per plant, total number of fruits per plant, total weight of fruits per plant combining high estimates of heritability and genetic advance is an indication of crop improvement through mass selection. Positive and significant phenotypic and genotypic correlation was observed between number of branches and total number of fruits per plant (0.67, 0.74) and total weight of fruits per plant (0.61, 0.67) suggested that selection for fruit yield on the basis of these traits will be effective. Meanwhile, significant and negative phenotypic and genotypic correlation between number of fruits per plant and fruit length (-0.30, -0.41) suggested that selection for fruit yield on the basis of these traits will not lead to increases in fruit yield.
INTRODUCTION
Solanum anguivi is a semi-cultivated non-tuberous Solanum sp. which is widely distributed in Africa (Schipper, 2000; Bukenya-Ziraba, 2004). The species has attained considerable importance in the South Eastern geographical zone of Nigeria. In this area, the edible immature fruits are consumed and used extensively in cultural ceremonies and traditional medicine, contributing to the sustainable production and demand for the crop. Solanum anguivi is polymorphic and exhibit diverse morphological characteristics including genetic variation in yield and fruit form (Schipper, 2000). The fruits are usually bitter, small in size with green color like the Asian pea eggplant Solanum torvum (Schippers, 2004). However, some Nigerian local cultivars have medium to big fruits with variable colors (e.g., white, cream colors) and slightly sweet taste which can be introduced into different varieties. Genetic improvement of S. anguivi with increases in the yield and quality of fruit characteristics will further enhance the social value of the crop and the contribution to poverty alleviation and better nutrition in the zone. But, so far, not much has been achieved with the breeding of the crop and information in this area is scanty and not readily available. Bukenya-Ziraba (2004) reported that S. anguivi has a potential use as a genitor in breeding for disease resistance in Solanum aethiopicum. He further suggested that traits such as plant habit, earliness, fruit quality and yield should be considered during selection and breeding.
In order to achieve rapid genetic improvement of the crop, the available population pool can be exploited for genetically desirable traits which can be selected and combined in various forms to produce improved varieties. Determination of heritability estimates, using different methods has been reported by various authors including (Wray and Visscher, 2008; Obilana and Fakorede, 1981; Johnson et al., 1955). The value of heritability estimates is enhanced when used together with the selection differential or genetic advance. Combined high heritability estimate and genetic advance is an indication that variation is attributable to high degree of additive effect and selection would prove useful (Panse, 1957). Heritability estimates for yield-components in different crops have been reported in other breeding programmes e.g., tomato (Foolad et al., 2006); peanut (Ekvised et al., 2006) and in exotic and local eggplant (Islam and Uddin, 2009). Information on the amount and direction of association between yield and yield related characteristics is important for rapid progress in selection and genetic improvement of a crop (Binodh et al., 2008). This will indicate the interrelationship between two or more plant characters and yield, providing suitable means for indirect selection for yield. The characters associated in a significant and positive direction with the fruit yield and other desirable traits including the quantity and fruit size are important for the development of improved and more acceptable varieties of S. anguivi.
This study is aimed at determination of traits with appreciable level of heritability estimates, genetic advance and which are in positive association with the fruit yield of Solanum anguivi.
MATERIALS AND METHODS
The experiment was carried out at the horticultural unit of Babcock University Ilishan Remo, Ogun State during the rainy season through the dry season in 2009. The experimental site is located in the rain forest agro-ecological vegetation at latitude 6°43 E and longitude 6°5 N of the equator in the South-Western Nigeria. A total of eighteen accessions collected from various sources including home gardens, farmers’ plots, private collections and market places were used in the study (Table 1). The seeds were sown in plastic trays in the nursery in March and the seedlings were transplanted 5-6 weeks after sowing on the field. The seedlings were planted on raised beds in two rows per bed with spacing of 30 cm between plants within each row and 50 cm between rows. Before planting, poultry organic manure was incorporated into the beds at the rate of 20t per h. The eighteen accessions were each planted in 2.0x4.0 m plot and replicated four times in Randomized Complete Block Design (RCBD). Data was collected on agronomic characters including:
| • | Plant height (cm) |
| • | Mean fruit yield (g) |
| • | Number of branches per plant |
| • | Number of fruit set per plant` |
| • | Fruit length (cm) |
| • | Fruit width (cm) |
| Table 1: | List of accessions with some agronomic characteristics |
Data analysis: Data collected on the quantitative characters were analyzed using SAS Microsoft windows 8.0 (SAS, 1999), employing the method outlined by Steel and Terrie (1980). The yield and yield component was used to determine the genotypic and phenotypic variances according to Prasad et al. (1981). The variance components was used to compute the Genotypic Coefficient of Variability (GCV), Phenotypic Coefficient of Variability (PCV), broad sense heritability and expected genetic advance, according to the methods of Burton (1952), Johnson et al. (1955) and Kumar et al. (1985). Estimates of genotypic and phenotypic correlation coefficients among the characters were obtained using the formula of Miller et al. (1958).
RESULTS/DISCUSSION
The mean square obtained from analysis of variance showed significant differences (p≥0.01 Table 2) for plant height at maturity, branches per plant, total number of fruits per plant, total fruit weight per plant and fruit width, whereas fruit length was not significantly different (p≥0.01 Table 2) among the accessions. This suggested sufficient amount of variation among the accessions (Ibrahim and Hussein, 2006). This agrees with the report of Dar and Sharma (2011), Kitila et al. (2011), Singh et al. (2011), Gandhi et al. (2001) and Mostofa et al. (2002).
Generally, the values of PCV are slightly higher than that of GCV. This agrees with the report of Jalata et al. (2011) in barley. The difference can be accounted for by environmental influence. PCV ranged from (11.62) for fruit width to (58.17) for total fruit weight (Table 3). Similarly GCV ranged from (9.45) for fruit width to (54.25) total weight of fruits per plant. High PCV and GCV values which was observed in total fruit weight and number of branches per plant, suggested that these characters account for the highest variation in S. anguivi. This also agrees with the report of Aragaw et al. (2011), Kitila et al. (2011), Kotal et al. (2010), Ibrahim and Hussein (2006) and Vijay and Manohar (1990). Phenotypic and genotypic variance is highest in total weight of fruits per plant (3219.01 and 2799.39) and least in fruit width (0.03 and 0.02), respectively. The estimates of broad sense heritability among the characters varied from moderate to high.
| Table 2: | Mean squares of six fruit and yield related characters of eighteen Solanum anguivi accessions in Ilishan-Remo Nigeria during rainy-dry season |
| **Significant at 1% (p≥0.01) level of probability | |
| Table 3: | General mean, estimate of phenotypic and genotypic variance, phenotypic and genotypic coefficient of variability, broad sense heritability and genetic advance expressed for eighteen Solanum anguivi accessions |
For plant heritability and genetic advance expressed for eighteen Solanum anguivi accessions height at maturity (76.67), number of branches per plant (83.9), total number of fruits per plant (85.5), total weight of fruits per plant (86.96) and fruit width (66.15). This indicates that these characters are under the influence of additive gene effect and therefore suggests that any selection in S. anguivi based on the phenotype of these characters will be effective in fruit yield. This agrees with the report of Parthiban et al. (2011) and Nwangburuka (2010). High genetic advance was also recorded in number of branches (64.36), total number of fruits per plant (98.87) and total fruit weight per plant (104.21). However, heritability estimate alone is not enough to produce a high genetic gain (Ibrahim and Hussein, 2006). Thus traits like number of branches per plant, total number of fruits per plant, total weight of fruits per plant combining both high genetic advance and high estimates of heritability is a more reliable indicator of additive gene action and therefore, their improvement can be achieved through mass selection (Randhawa and Sharma, 1972; Ibrahim and Hussein, 2006). Plant height at maturity and fruit width withmoderate estimates of heritability and genetic advance suggested that these traits may be under the control of non-additive gene action and environmental effect (Subramayan et al., 1995). The phenotypic and genotypic correlation coefficient indicated that plant height at maturity was positively and significantly correlated with number of branches per plant (0.55, 0.56), total number of fruits per plant (0.64, 0.69) and total weight of fruits per plant (0.54, 0.60) (Table 4). Similarly, positive and significant phenotypic and genotypic correlation was observed between number of branches and total number of fruits per plant (0.67, 0.74); total weight of seed per plant (0.61, 0.67). There was also significant positive phenotypic and genotypic correlation between total number of fruits per plant and total weight of fruits per plant (0.96, 1.01); fruit width (0.39, 0.54). This was suggested that selection for fruit yield on the basis of these traits will yield reliable result. However, significant and negative correlation at Phenotypic and genotypic level between total number of fruits per plant and fruit length (-0.30, -0.41), total fruit weight and fruit length (-0.30, -0.48) suggested that selection directed towards fruit yield based on fruit length will not produce any significant improvement.
| Table 4: | Phenotypic, genotypic and environmental correlation coefficient among five characters of Solanum in Ilishan-Remo |
| **Significant at 1% (p≥0.01) level of probability. ns: Not significant | |
This agrees with the report of Malik et al. (2000) and Gondane et al. (1995).
CONCLUSIONS
This study concludes that number of branches per plant, total number of fruits per plant and fruit width with high heritability and genetic advance should be taken into consideration in selection for fruit improvement in Solanum anguivi. It further concludes that variability S. anguivi is accounted for by the fruit weight and branching characteristics.