Estimates of genetic parameters of fruit quality traits in teasle gourd ( Momordica subangulata Blume . subsp . renigera )

The present investigation was carried out to assess genetic variability, heritability and genetic advance in five genotypes of teasle gourd. The experiment was laid out in a randomized block design with four replications. High phenotypic coefficients of variation were observed for all characters except ascorbic acid in excoarp, ascorbic acid in mesocarp, total soluble solids (TSS) in exocarp, b-carotene in exocarp, acidity in mesocarp, b-carotene in mesocarp, TSS in mesocarp, acidity in exocarp which showed high heritability coupled with high genetic advance indicating that these traits were gene control and simple phenotypic selection can be used for further improvement of these traits. Fruit weight, which showed the highest positive direct effect on fruit yield also showed positive correlation with β-carotene in exocarp. The most important fruit quality influencing traits from the study includes TSS content of exocarp and mesocarp since these traits character showed positive correlations with most important fruit quality characters.


INTRODUCTION
The teasle gourd (Momordica subangulata Blume ssp.renigera) belongs to the family Cucurbitaceae.It is probably native to India.It is dioecious in nature and a perennial climber with tuberous roots mainly cultivated in Assam, West Bengal, Bihar, Orissa, North-eastern States, Maharashtra, Gujarat and Andaman Islands.The fruits are highly nutritious and the unripe fruits are very astrinegent and can be used as an appetizer.Estimates of various parameters for assessment of genetic variability including mean range of variation, heritability, genetic advance and coefficients of variation help plant breeders in designing suitable plant types through improvement in quantitatively inherited traits.Correlations provide an estimate of the degree and direction of association among various components of yield.It is therefore, essential to determine the contribution of various variables to the observed association and partition the correlation coefficient into components with direct and indirect effects.Hence, the present investigation was undertaken.

MATERIALS AND METHODS
The experimental materials consisted of five female clones *Corresponding author.E-mail: abhishek.hort@gmail.com.The mean data were subjected to analysis of variance (Panse and Sukhatme, 1984), coefficient of variation and heritability (Burton and de Vane, 1953) and genetic advance in percent of the mean (Johnson et al., 1955) and the correlation coefficient analysis was done according to A1- Jibouri et al. (1958).

Genetic variability for fruit quality characters based on mean performance
The mean of the 17 fruit characters recorded in the female clones is presented in Table 1.The data for different characters namely, fruit weight at marketable stage (g), ovary diameter (mm), fruit length at marketable stage (cm), fruit breadth at marketable stage (cm), pericarp thickness at marketable stage (mm), TSS in exocarp (°Brix), TSS in mesocarp (°Brix), acidity in exocarp (%), acidity in mesocarp (%), ascorbic acid in exocarp (mg/100 g), ascorbic acid in mesocarp (mg/100 g), total sugar in exocarp (%), total sugar in mesocarp (%), reducing sugar in exocarp (%), reducing sugar in mesocarp (%), β-carotene in exocarp (mg/100 g fresh) and β-carotene in mesocarp (mg/100 g) showed variation among the female clones and ascorbic acid content was very high between 103.02 mg/100 g fresh weight in Assam Local and 278.77mg/100 g fresh weight in Purulia Local-1 suggesting ample scope for enhancing ascorbic acid content in the fruits through selection.Contents of TSS, acidity and sugar were much higher in the mesocarp of the fruit while, ascorbic acid and βcarotene contents were much higher in the exocarp of the fruits (Table 1).These findings abnegate peeling of the fruits during preparation of dishes.Dubey and Gaur (1990), Awasthi et al. (1988), Naik et al. (2012) and Bharathi et al. ( 2013) also estimated different proximate.

Analyes of variance
Analyses of variance for the 17 characters were computed separately for two years along with the pooled data.Mean sums of squares presented for 17 characters, (Table 2) clearly show significant differences among the female clones for all the characters except some fruit quality characters including pericarp thickness at marketable stage, TSS in exocarp, acidity in exocarp and acidity in exocarp at 1% level of significance.

Coefficient of variation (CV)
The coefficient of variation (Table 3) was very low for most of the characters except fruit breadth at marketable stage (21.09%),pericarp thickness at marketable stage (14.04%),acidity in mesocarp (19.89%), β-carotene content in exocarp (12.42%) and mesocarp (17.40%).In these characters, a comparatively higher effect of the environment for the expression of the characters was evident.

Broad sense heritability
Broad sense heritability estimates were high ranging from 83.50 to 99.4% for most of the characters, moderate ranging from 71.6 to 72.3% for acidity in mesocarp and β-carotene in mesocarp whereas it was very low for fruit breadth at marketable maturity and pericarp thickness at marketable stage (Table 3).However, the broad sense heritability values are likely to be overestimated since in this calculation, it was not possible to exclude variation due to different genetic components and their interrelations.

The effect of GCV, heritability and GA combined
In the present investigation, high GCV coupled with high broad sense heritability and high genetic advance were observed in four fruit quality characters namely, ascorbic acid content in mesocarp, total sugar content in exocarp, total sugar content in mesocarp and β-carotene in exocarp (Table 3).According to Panse (1957), such situations may arise due to additive gene action controlling the characters.So, these characters can well be included in the improvement programme through selection.It is predicted that early generation selection would be helpful for improving these characters.A high to moderate heritability coupled with moderate genetic advance was recorded for TSS in exocarp (°Brix), TSS in mesocarp (°Brix), acidity in exocarp (%), acidity in mesocarp (%), ascorbic acid in exocarp (mg/100 g) and β-carotene in mesocarp indicating that these characters could also be improved by selection in early generation.However, selection could also be applied following repeated evaluation over the years.A moderate to high heritability accompanied with low genetic advance was recorded (Table 3) for fruit weight at marketable stage (g), ovary diameter (mm), fruit length at marketable stage (cm), fruit breadth at marketable stage (cm) and pericarp thickness at marketable stage (mm).Improvement of these characters needs long term evaluation to ascertain the efficacy of selection for these characters because such association of genetic parameters may be attributed to non-additive gene action.

Correlations among the fruit quality characters
In the present study, the magnitude of genotypic correlation coefficient was higher than phenotypic correlation coefficient in most of the pairs of character under study (Table 4).In general though, the genotypic and phenotypic correlation coefficients agreed closely which indicated less influence of environment on the correlated response of pairs of characters involved.In the situation of environmental influence on the joint expression of the characters, there is always a possibility of over estimation of genotypic correlation coefficient.Hence, phenotypic correlation coefficients between pairs of traits have been utilized to study trait associations.In the present investigation, most of the characters did not show significant phenotypic correlations.However, 28 pairs of traits showed significant positive correlations including: 1) Fruit weight at marketable stage and ovary diameter.2) Fruit weight at marketable stage and fruit length at marketable stage.
3) Fruit weight at marketable stage and β-carotene in exocarp.4) Ovary diameter and fruit length at marketable stage.5) Ovary diameter and β-carotene in exocarp.6) Fruit length at marketable stage and acidity in mesocarp.Fruit weight, which showed the highest direct positive effect on fruit yield also showed positive correlation with β-carotene in exocarp which strongly suggests the possibility of simultaneous enhancement of fruit yield and βcarotene in exocarp of the fruit through selection of fruit weight in the positive direction.
The phenotypic corre-lation coefficients revealed associations among most of the fruit quality traits.However, the most important fruit quality influencing trait including TSS content of exocarp and mesocarp showed positive correlations with most of the important fruit quality characters.

Selection indices for fruit yield and quality
Important selection indices have been determined from the studies of genetic variability and character associations.Fruit weight emerged as the most important character influencing both fruit yield and fruit quality particularly β-carotene content.Number of fruits per plant also justified its importance as another prime fruit yield component.It is encouraging to note that the prime quality traits such as ascorbic acid and β-carotene did not exert negative effects on each other.However, TSS content of the fruit emerged as the most influential fruit quality determining character.Hence, selection in teasle  gourd must be applied on fruit weight, number of fruits per plant, fruit yield per plant and TSS content of the fruit for simultaneous improvement of both fruit yield and quality.
Broad sense heritability: Broad sense heritability estimates were high ranging from 83.50 to 99.4% for most of the characters and moderate ranging from 71.6 to 72.3% for acidity in mesocarp and β-carotene in mesocarp.
GCV, heritability and GA combined: High to moderate heritability coupled with moderate genetic advance was recorded for TSS in exocarp (°Brix), TSS in mesocarp (°Brix), acidity in exocarp (%), acidity in mesocarp (%), ascorbic acid in exocarp (mg/100 g) and β-carotene in mesocarp indicating that these characters could also be improved by rigid selection in early generation.However, selection could also be applied following repeated evaluation over years.

Correlations among fruit quality characters
In the present investigation, most of the characters did not show significant phenotypic correlations.However, 28 pairs of characters showed significant positive correlations.Fruit weight, which registered the highest positive direct effect on fruit yield also showed positive correlation with β-carotene in exocarp.The most important fruit quality influencing trait study include TSS content of exocarp and mesocarp since this character showed positive correlations with most of the important fruit quality characters.

Important selection indices for fruit yield and quality
Fruit weight emerged as the most important character influencing both fruit yield and fruit quality particularly βcarotene content.Number of fruits per plant was as the other prime fruit yield component.It is encouraging to note that the prime quality traits namely, ascorbic acid and β-carotene did not exert any negative effect on each other.TSS content of the fruit emerged as the most influential fruit quality determining character.Hence, selection in teasle gourd must be performed on fruit weight, fruits per plant, fruit yield per plant and TSS content of the fruit for simultaneous improvement of both fruit yield and quality.

Table 1 .
Mean fruit and fruit quality characters in five female clones of teasle gourd.
of bamboo strips and nylon wire net.A general fertilizer dose at 150 kg N, 60 kg P 2 O 5 and 40 kg K 2 O per hectare were applied.One-third of the dose of nitrogen along with the phosphate and potash fertilizers was applied given as a basal application while the rest of the N was top dressed in two split doses, at 80 days after planting and the remainder, one month later.Five plants of

Table 2 .
Analysis of variance for different fruit quality characters.

Table 3 .
Genetic parameter estimates for different fruit quality characters.