Genetic variability and field performance of some sweet gourd (Cucurbita moschata Duch) accessions

For Any Information: ask.author@journalbinet.com The experiment was conducted at the field and laboratory of “Collection, Evaluation, Conservation and Utilization of Landraces and Wild relatives of Some Important Vegetables and Fruits in Bangladesh (CVFB)” project, Department of Horticulture, Bangladesh Agricultural University, Mymensingh. Studies on field performance and genetic variability of sweet gourd accessions were carried out using morphological traits. Analysis of variance for different characters showed high degree of variation among the 43 accessions. The accession CM152 showed the best performance in respect of yield per plant (57.8 kg). The highest average fruit weight (10.43 kg) was recorded in CM154. Regarding the number of fruits per plant, CM145 produced the maximum number of fruits per plant (10.0). In all the traits genotypic coefficient of variation was smaller than phenotypic coefficient of variation. High heritability with genotypic and phenotypic coefficient of variation was observed for vine length at final harvest, number of male flowers per plant, node for first male flowers, average fruit weight, fruit cavity length and breadth, dry weight of 100 g flesh and number of seeds per fruit indicating additive gene effects of these traits. Citation: Nahar, M. A., Begum, S., Rabbani, M. G. & Karim, M. R. (2016). Genetic variability and field performance of some sweet gourd (Cucurbita moschata Duch) accessions. Journal of Science, Technology and Environment Informatics, 04(02), 301-312. © 2016, Nahar et al. This is an open access article distributed under terms of the Creative Common Attribution 4.0 International License.


I. Introduction
Sweet gourd (Cucurbita moschata Duch) is an important vegetable in Bangladesh as well as in the world (Nahar et

II. Materials and Methods
The experiment was conducted at the field and laboratory of "Collection, Evaluation, Conservation and Utilization of Landraces and Wild relatives of Some Important Vegetables and Fruits in Bangladesh (CVFB)" project, Department of Horticulture, Bangladesh Agricultural University, Mymensingh during the period from October 2003, to April, 2005. Forty three local sweet gourd genotypes were included in this study. The materials were collected by 'CVFB' project from different parts of Bangladesh which have been described previously (Nahar et al., 2005). The experiment was conducted to evaluate the variability, character association and field performance and genetic divergence of 43 sweet gourd accessions. Each sweet gourd accession was considered as an individual treatment of the experiment. Therefore, there were 43 treatments in this experiment. The sources of the sweet gourd accessions have described previously (Nahar et al., 2005). The experiment was laid out in randomized complete block design with three replications. One accession represented one treatment and two plants in an accession considered one replication. The unit plot was 12 m 2 maintaining a distance of 0.5 m between the plots. Treatments were randomly assigned to different plots of each block separately. The organic and inorganic fertilizers were applied at the rate of 15 ton cowdung, 12 kg triple super phosphate (TSP), 150 kg urea and 100 kg muriate of potash (MoP) per hectare, respectively (BARC, 1997). Fifty percent cowdung was applied at the time of final land preparation. The remaining cowdung, entire quantity of TSP and half of each urea and MoP were applied as basal dose during pit preparation. The rest of urea and MoP were top dressed in two installments at 30 and 50 days after transplanting. Three plants were selected at random from each plot for recording data. Data on different parameters were collected at vegetative and reproductive stages, and on fruit characters as well. The significance of different among the means was evaluated by least significant difference (LSD) test for interpretation of the result (Gomez and Gomez, 1984).

III. Results and Discussion
Variability and characterization of vegetative characters among 43 sweet gourd accessions Results on variability and character association of different vegetative characters of 43 sweet gourd accessions have presented in Table 01 and Table 02. Estimation of genotypic and phenotypic variances was fairly high for vine length at 60 DAD and at final harvest but comparatively lower at 30 DAD (Table 02). Genotypic coefficient of variation was also lower than the corresponding phenotypic one, which indicated the larger influence of environment. There were also considerable differences between genotypic and phenotypic coefficient of variation. Comparatively low difference between GCV and PCV (16.04% and 16.10%) was exploited by vine length at final harvest (   (Table 02). Vashistha et al. (1983) reported high heritability in water melon.

Number of primary branches:
Significant difference was observed for number of primary branches among the accessions. The highest number of primary branches (16.84) was observed in CM133 followed by CM132, CM153, CM154 and CM164. The lowest number of primary branches (8.58) were found in CM149 which was statistically similar with CM150, CM151, CM148 and CM156. The range lies between (8.58 -16.84) with the average mean value of 12.59 that indicated moderate variability among the accessions for this trait (Table 01). Genotypic (2.82) and phenotypic (5.11) variances and its coefficient of variations (13.33 and 17.94%, respectively) were observed (Table 02). The difference between GCV and PCV is quiet broader which indicated moderate environmental effect on the expression for this trait. Similar results was found by Rana et al. (1986) in pumpkin. Also moderate heritability (55.19%) was observed for this trait (Table 02).

Variability and characterization of reproductive characters among 43 sweet gourd accessions
Male and female flowers and sex ratio per plant: The range of variation was recorded in sex ratio (male: female) (5.03 -11.60) followed by female (4.66-11.66) and male flowers (51.00-91.66) per plant with the mean value of 7.71, 8.93 and 60.50, respectively among the reproductive characters (Table 03). These findings are in agreement with those reported by Chigwe (1991) in sweet gourd. Characters which showed high range of variation should be given priority in the selection (Vijay, 1987). From the average performance, the accession CM148 produced the maximum number of male flowers per plant (91.66) whileCM151 produced the lowest number of male flowers per plant (51.00) ( Table 03). The highest number of female flowers per plant (11.66) was recorded in CM143 and CM159. The lowest number of female flowers per plant (4.66) was found in CM154 which was statistically similar to CM136, CM152, CM155, CM156, CM149 and CM158 (Table 03).
The highest sex ratio (11.60) was recorded in CM147 and the lowest sex ratio (5.03) was observed in CM165 with mean value of 7.71 (Table 03). In cucurbits sex ratio varies from 15:1 to 30:1, the former condition is advantageous and economical because it results in greater number of pistillate flowers per plant consequently higher fruit set and yield (Bose and Som, 1986   Days to first female flower: This is an important character that influences the yield. Accession CM134 required maximum days to first female flowering (68.33 days) which was followed by CM133, CM135, CM147, CM148 and CM149 minimum days required for first female flowering was (57.16 days) in CM131 followed by CM136, CM137, CM155, CM156 and CM159 (Table 03). Among 43 accessions the phenotypic variance (10.70) was quite closer with the genotypic variance (6.5). Also narrow difference was observed between PCV (5.32%) and GCV (4.14%) which indicated that this trait is genetically controlled. Estimated heritability was found 60.75% (Table 04). So the plant breeder should select this trait for breeding parameter. This result was similar with the findings of Islam et al. (1993) but dissimilar with Abusaleha and Dutta (1990).

Variability and characterization of yield and yield contributing characters among 43 sweet gourd accessions
Fruit length and diameter: The analysis of variance indicated a high degree of variation among the accessions for all the yield contributing characters. Among the accessions studied the longest fruit (50.33 cm) was recorded in CM154 which was followed by CM148 and CM162 with the mean value 34.77 cm. While the shortest fruit was found in CM173 (22.00 cm) followed by CM131 and CM132. The highest fruit diameter (82.00 cm) was recorded in CM160. The lowest fruit diameter was recorded in CM173 (45.00 cm) and followed by CM131 (Table 05).
A high difference between genotypic (49.36 and 29.14) and phenotypic (88.20 and 88.20) variances were found for fruit length and diameter, respectively. Comparatively moderate difference between GCV (15.53) and PCV (27.01) was found for fruit length whereas smaller difference between GCV (10.74) and PCV (14.36) were recorded for fruit diameter. Sharma et al. (2000) observed similar result in cucumber. For fruit length and diameter heritability was found 33.04% and 55.96%, respectively (Table 06). Number of fruits per plant: From Figure 01 it was observed that the maximum number of fruits per plant (10.00) was produced by CM145 which was significantly different from the other accessions. The accession CM143, CM144, CM151 and CM172 also produced higher number of fruits and were statistically alike. The minimum fruit bearing (5.00 per plant) was observed in CM136 and followed by CM159, CM160, CM163 and CM164 (Figure 02). Saha CM132  CM133  CM134  CM135  CM136  CM137  CM138  CM139  CM140  CM141  CM142  CM143  CM144  CM145  CM146  CM147  CM148  CM149  CM150  CM151  CM152  CM153  CM154  CM155  CM156  CM157  CM158  CM159  CM160  CM161  CM162  CM163  CM164  CM165  CM166  CM167  CM168  CM169  CM170 (Table 05). The difference between GCV (24.91%) and PCV (24.97%) of this character was narrow confirming the least environmental influence. This trait was highly heritable (99.55%) (Table 06).  Yield per plant: The accession CM152 gave the highest yield per plant (57.80 kg) followed by CM134, CM138 and CM170 (Figure 03). The lowest yield (9.73 kg) was found in CM131 followed by CM173 ( Figure 03). Yield per plant showed the mean value (30.56 kg) per plant with high GCV (32.33%) and PCV (44.13%). Moderate heritability (53.66%) was observed for this trait (Table 06). The present findings are in agreement with Saha et al. (1992) and Ahmed (1988). In the present study heritability estimates were high for fruit weight (97.90%), fruit cavity length (96.70%), fruit cavity breadth (99.58%), flesh thickness (96.92%), dry weight of 100 g flesh (99.55%) and yield (53.66%) which indicated that these characters were less influenced by environment. High heritability value would be most effective condition for selection. Therefore effective selection could be made for these traits.

V. Conclusion
Results revealed that wide variability exists among the sweet gourd accessions used in the present experiment. This variability can be used for selection of superior genotypes for cultivation at farmers' level as well as breeding for developing new varieties of sweet gourd. Selection criteria should include characters such as fruit length, fruit diameter, number of fruits per plant and average fruit weight for the development of high yielding varieties of sweet gourd. Further collection of sweet gourd germplasm should be continued for wider genetic variability and selection of desired traits.