The analysis of variance revealed that genotypes exhibited significant differences (Table 1) in respect of all the traits at 1% level of significance. While, pod width registered significant differences among the genotypes at 5% level of significance. Two characters’ mature pod weight and pod length did not exhibit significant differences among genotypes. The highest variation was observed for pod yield per plant (45225.41**), number of pods per plant (1959.54**) (Table 1). Such a high variability for the above characters was also reported earlier by
Narayanankutty et al., 2003;
Thangam et al., 2020.
Nkoana et al., 2019 reported highly significant differences among the accessions for all the traits in cowpea.
Assessment of Per se performance
Lack of information on germplasm characterization and evaluation restricts the effective use of germplasm
(Kuldeep et al., 2019). Introduction and using them as parents in further improvement is one of the option, hence the exotic cultivars included in the study will be highly useful for vegetable cowpea improvement in India. In general, exotic collections followed by indigenous collections were superior (Table 2) for flowering and maturity traits based on per se performance, while, in respect of yield and its attributes, check varieties were superior followed by indigenous collections. In view of earliness reported in the present study, exotic collections can be further involved in suitable breeding programme with Indian varieties to incorporate earliness. When the seed colour (Fig 1) of all the studied genotypes was examined, greatest variation displayed by accessions that inherits from generation to generation as seed colour is a qualitative trait. Hence, the present germplasm offers wider scope to serve the consumer preferences based on the seed colour.
Flowering characters
With respect to days to first flowering, EC-244018 (37 days) was earlier to flower (Table 3) followed by EC-390231, Kashi Unnati, IC-333106 and IC-91456, which were at par, while four genotypes
viz., EC-390266, EC-724452, EC-724775 and IC-206240 were late to flower, which took 65.50 days among all the genotypes. In regard to days to 50 per cent flowering, EC-244018 (41 days) followed by EC-390231, IC-333106, IC-91458 (41.50 days) and IC-20645 (42 days), Kashi Unnati, IC-249141, IC-257427, IC-219481 (43 days) and EC-390225 (43.50) were at par. While, IC-206240 and EC-724775 (71days) followed by EC-715197 (69.50 days) were very late to come to 50 per cent flowering among the genotypes studied. Sizeable amount of divergence among the cowpea germplasm was reported earlier by
Hira Lal et al., 2018, which is in line with the present investigation results.
Maturity characters
For days to first maturity, among the all the 87 genotypes, two genotypes, EC-290231 and IC-91458 (44.50 days) followed by EC-24018 and IC-333106 (46 days) were earlier to first maturity compared to rest of the genotypes. Around 19 genotypes had produced beans with early maturity than early maturing check variety Kashi Unnati (48 days). Whereas, two genotypes
i.e., IC-206240 and EC-724712 (75.50 days) followed by another 4 genotypes, took longer days to first maturity. For days to first harvest, EC-390231 and IC-91458 (50.50) followed by IC-333106 (51 days), EC-724374 and EC-724364 (51.50) and EC-724484 (52 days) were earlier among the genotypes. As many as 16 genotypes were earlier to harvest to early duration check, Kashi Unnati (53 days). Two genotypes, EC-715197 (80.50 days) and EC- 724712 (81 days) had taken more days for first harvesting of matured beans. The present results are in tune with the reports of
Valarmathi and Surendran, 2007.
Pod attributing traits
Length wise, longest pods were produced by Kashi Unnati (41 cm), while shorter pods were exhibited by three genotypes
viz., EC-725159 (9.35 cm) followed by EC-738091 (9.90 cm) and EC-724873 (10.70 cm). Wider pods were produced by EC-390231, EC-390204 (1.1 cm) followed by EC-72398, EC-244018, EC-390223 and IC-257427 (1.05 cm) and another 2 genotypes with more than 1cm pod diameter. Lowest pod diameter of 0.79 cm was registered by Kashi Unnati and more than 20 genotypes produced at par breadth measuring pods, which were at par. Similar reports are presented by
Buleti et al., 2020.
Kashi Unnati produced on an average of 19.50 gram weight green pods, which was highest among all the genotypes included in the study. As many as eight genotypes produced green pods with their pod weight ranging from 7.29 g to 9.18 g, which was more than the higher weight pod bearing check variety, Arka Suman (6.9 g). In respect of number of pods per plant, EC-724364 had produced highest number of 140.50 pods. Eleven genotypes produced more number of pods ranging from 65.20 (IC-97806) to 140.50 (EC-724364) pods compared with higher number pod producing check variety, Arka Suman (64 pods).
Owade et al., (2020) indicated cowpea pods and leaves can be consumed as boiled, blanched, dried, or fermented vegetables, which is cheaper source of protein. Always varieties with numerous pods are always appreciated by the farmers. Highest numbers of 41.5 seeds per pod were produced by Kashi Unnati. No germplasm produced good number of seeds per plant compared to all the four higher yielding check varieties included in the study. As many as 31 genotypes produced more seeds ranging from 16 to 18 per pod.
Buleti et al., 2020 2020 reported that days to maturity, pod size and pods per plant revealed significant differences among the cowpeas.
Green pod yield per plant
Among the genotypes, with respect to green pod yield per plant, EC-390210 produced maximum of 736 grams green pod yield per plant (Table 3). Another 10 genotypes produced per plant green pod yield, ranging from 311.60 grams to 497.45 grams compared to high yielding check variety, Kashi Kanchan (309.50 g). The yield of cowpea has generally remained below the potential of the crop as farmers grow cowpea on marginally fertile and infertile soils. So, evaluation of germplasm for high yield is a regular criterion to identify new varieties. In this direction, from the present investigation, the out yielding accessions like EC-390210 can be evaluated in multi-locational trials before they are released for commercial cultivation.
Morris et al., 2020 reported that eight Indian cowpea accessions produced significantly high protein content averaging 24.423% and pod yield and protein content had positive correlation. Higher yield always fetches good protein to diet. As reported by Molosiwa and Makwala, 2020, introduced genotypes performed better for nine of the characters, revealing the advantage of introduced genotypes, when twenty four cowpea genotypes were evaluated in field conditions for three consecutive seasons. The present study confirmed the same. Accessions without yield performance compared with check varieties are reported in different crops
(Saidaiah et al., 2021 in jack bean;
Ravi et al., 2021 in cluster bean;
Pidigam et al., 2021).
Genetic variability studies
With respect to range, pod yield per plant (1.90-751.30) followed by the number of pods per plant (0.50-140.50). Khanpara
et al., 2015 reported the highest range of variation for pod yield per plant in vegetable cowpea. In all the traits, all the characters exhibited narrow differences between the value of PCV and GCV (Table 4). This indicated a low impact of the environment on the expression of all the quantitative characters. The same was reported earlier by
Narayanankutty et al., (2005) and Thangam
et al., 2020. The higher estimates of GCV and PCV (>20%) were registered by pod width (57.68, 58.18), mature pod weight (41.48, 41.67), the number of pod per plant (87.70, 87.70) and pod yield per plant (95.72, 95.82), respectively. The higher estimate of PCV over the corresponding GCV values for the characters studied indicate the influence of environmental factors in the expression of the traits under various environmental conditions. The higher estimates of GCV and PCV (>20%) for pod width, mature pod weight, number of pod per plant and pod yield per plant, indicate the scope for selection of these traits for further improvement.
Narayankutty et al., (2003) and
Vavilapalli et al., (2013) have reported in tune with the present results for green pod yield and its components in vegetable cowpea.
Thangam et al., 2020 and
Narayanankutty et al., (2003) reported high GCV for yield per plant and pod weight in vegetable cowpea. Low GCV values for days to first flowering and number of seeds per pod have been reported by
Sreekumar et al., (1996). High to moderate GCV and PCV values were found for number of pods per plant, pod yield per plant, pod weight, number of seeds per pod and pod length
(Arup et al., 2014; Morris et al., 2020).
The higher values of heritability in the broad sense (>60%) were registered with all the traits ranging from 94% for pod length to 100 percent in case of days to first fruit set, number of pods per plant and pod yield per plant. Wide variation was observed for all these characters in the present study. Similar findings have been reported by other workers (
Narayanankutty et al., 2005;
Thangam et al., 2020).
With the help of variability and subsequent GCV alone, it is not possible to determine the amount of genetic variation that is heritable to the further generations.
Burton and De Vane (1953) suggested that GCV combined with estimates of heritability would give the best results of genetic advance to be expected from the selection. In the present study, heritability values were high (>90%) for all the characters studied. High values of heritability for quantitative characters have also been reported by
Thangam et al., 2020 and
Narayanankutty et al., (2003). The accurate value for heritable variation can be estimated when heritability is combined with genetic advance. In the present study, high heritability coupled with high genetic advance was observed for pod yield per plant (g) and number of pods per plant. This may be due to the preponderance of additive gene action for these characters thereby indicating the advantages of selection for their improvement. High heritability coupled with high genetic advance for the above characters in vegetable cowpea has been reported by
Narayanankutty et al., 2003;
Kamara et al., 2017;
Morris et al., 2020; Thangam et al., 2020. The value of PCV and GCV more or less equal were observed in the remaining characters which indicated that these characters were less influenced by the environment. High heritability along with high genetic advance was observed for green pod yield per plant, pod length, pod width and number of pods per plant also reported earlier by
Khanpara et al., 2015. Other characters
viz., days to first flowering, days to 50% flowering, days to first fruit set, pod length, pod width, mature pod weight and number of seeds per pod has recorded high heritability of more than 90 percent but their genetic advance is very low (<30%) indicating the non-additive gene action for these traits. This implies the improvement of the above traits by pyramiding desirable genes through suitable hybridization programs.
The perusal of data revealed that the maximum coefficient of variation was recorded for pod width (7.66) followed by green pod yield per plant (4.45), pod weight (3.88) and pod length (3.63). The rest of the CVs for the rest of the characters among the genotypes exhibited less. It indicates that the characters measured with low CV are least influenced by environmental changes. In field experiments, higher CV is generally recorded due to heterogeneous properties of the climate and soil as well. The present study results showed that the heterogeneous conditions are eliminated to the extent possible; hence, true genotypic effects are reflected in the CV. The cowpea is predominantly self-pollinated and hence, the CV reported is supported with earlier findings of
Thangam et al., 2020 in cowpea. Hence, selection of parents differing in traits such as pod width, follow, green pod yield per plant, pod weight and pod length will be more useful in future breeding programs.
Genotypic correlation studies
The genotypic correlation studies provide reliable information on the nature and extent of relationship for bringing about improvement in yield and other traits. Days to first flowering were positive and significantly correlated (Table 5) with days to 50% flowering, days to first fruit set and days to first harvest, pod width, while negative and significantly correlated with no. of pods, no. of seeds per pods and pod yield per plant. Days to 50% flowering was positive and significant in correlation with days to first flowering, days to first fruit set and days to first harvest, at the same time significant and negatively correlated with no of pods, number of seeds per pods and pod yield per plant. Important maturity parameters days to first fruit set and days to first harvest were positively and significant among them and the other three maturity parameters. These two characters were significant and negative in correlation with yield and yield parameter
i.e., pod width, pod weight, number of pods, number of seeds per pods and pod green yield per plant.
Pod length was negative and significant with days to first fruit set and positive significant with mature pod weight and pod yield per plant, whereas, pod width was correlated as significant and negative with flowering parameters (days to first flowering and days to 50% flowering), maturity parameters (days to first fruit set and days to first harvest) and significant and negative with yield and yield attributes (mature pod weight, number of pods, number of seeds per pods and pod yield per plant). The mature pod weight was positive and significant in correlation with pod length and pod yield per plant. The number of pods, number of seeds per pods and pod yield per plant was negatively correlated with flowering parameters (days to first flowering and days to 50% flowering) and maturity parameters (days to first fruit set and days to first harvest), while, the correlation of number of pods per plant were positive and significant with pod width, number of seeds per pods and pod yield per plant. The numbers of seeds per pod were significant and positive with pod width, number of pods and pod yield per plant. Green pod yield per plant has a positive and significant correlation with pod length, pod width, mature pod weight, number of pods and number of seeds per pods. This is in accordance with the results of
Narayanankutty et al., (2005);
Pidigam et al., 2019;
Morris et al., 2020; Thangam et al., 2020.
Nkoana et al., 2019 reported positive and significant correlations of grain yield per hectare with the number of pods per plant and grain yield per plant in vegetable cowpea.
