The analysis of variance revealed highly significant differences among the parents and their hybrids for all the characters studied, indicating the presence of substantial amount of genetic variability in the material studied. This will offer a better opportunity to the plant breeder for selecting desirable genotypes (Table 1) and (Table 2). Earlier workers
viz.,
Kumar et al., (2017), Chauhan et al., (2018) found a similar result. The specific combining ability variance was higher than general combining ability variance and the ratio of SCA variance to GCA variance is higher than one for plant height, no. of clusters per plant, no. of pods per cluster, no. of pods per plant, seed yield per plant, biological yield per plant, 100 seed weight and harvest index, indicating a predominance of non-additive gene effect in the expression of these traits (Table 3).
Govindraj and Subramanian (2001),
Vaithiyalingan et al., (2002), Santha and Arulmozhi (2003),
Srividhya et al., (2005), Selvam and Elangaimannan (2010),
Gill et al., (2014), Chakraborty et al., (2010) and
Thamodharan et al., (2017) also reported involvement of non-additive genetic component in the expression of various characters.
On the other hand, GCA variance was higher than SCA variance for days to 50% flowering, pod length and no. of seeds per pod indicating involvement of additive gene effect in the inheritance of these characters.
Chakraborty et al., (2010) and
Surashe et al., (2017) also reported importance of additive genetic component in the expression of various traits.
Involvement of both additive and non-additive genetic components in the expression of different characters in blackgram had been also reported by
Chand (2001),
Thangavel et al., (2004), Karthikeyan et al., (2007), Ram et al., (2013) Shalini and Lal (2019) and
Bharathi et al., (2019).
General combining ability
The GCA effects of the parents presented in Table 4 depicted that none of the parents were found to be good general combiner for all the characters. An overall assessment of GCA effects revealed that among the lines, KUP 18-350, KUP 18-352 and KUP 18-345 were found to be a good general combiner for days to 50% flowering and plant height, here early flowering and short stature plants are desirable. Line KUP 18-346 was found to be a good combiner for no. of clusters per plant, no. of pods per plant, seed yield per plant, biological yield per plant, 100 seed weight and harvest index. Line KUP 18-350 was found to be a good combiner for Pod length, no. of seeds per pod and seed yield per plant. Line KUP 18-352 was found to be a good combiner for biological yield per plant, KUP 18-349 for no. of pods per plant and KUP 18-345 for harvest index.
Among the testers, Pant U-31 was found to be a good combiner for days to 50% flowering and no. of pods per plant, while Uttara for no. of clusters per plant.
Specific combining ability
The estimates of SCA effects presented in Table 5 revealed that out of 15 crosses only three cross combinations
viz., KUP 18-350 ×Pant U-31, KUP 18-345 × T-9 and KUP 18-345 × Uttara exhibited positive significant SCA effect for seed yield per plant. Out of 15 crosses, two crosses
viz., KUP 18-349 × Pant U-31 (-0.53) and KUP 18-352 × T-9 (-1.20) exhibited significant negative SCA effect for days to 50% flowering, indicated the possibility to develop the early maturity blackgram varieties. Beside this, three crosses
viz., KUP 18-345 × Pant U-31 (-4.99), KUP 18-352 × T-9 (-2.91) and KUP 18-349 × Uttara (-3.78) exhibited significant negative SCA effect for plant height, indicated the possibility to develop short stature blackgram varieties. Four crosses
viz., KUP 18-350 × Pant U-31 (2.80), KUP 18-349 × T-9 (1.82), KUP 18-346 × Uttara (1.68) and KUP 18-345 × Uttara (1.50) exhibited significant positive SCA effect for no. of clusters per plant; three crosses
viz., KUP 18-350 × Pant U-31 (0.32), KUP 18-346 × Pant U-31 (0.23) and KUP 18-345 × T-9 (0.30) exhibited significant positive SCA effect for no. of pods per cluster; two crosses
viz., KUP 18-350 × Pant U-31 (3.17) and KUP 18-345 × T-9 (3.20) exhibited significant positive SCA effect for no. of pods per plant; three crosses
viz., KUP 18-349 × Pant U-31 (0.16), KUP 18-352 × T-9 (0.22) and KUP 18-346 × Uttara (0.12) exhibited significant positive SCA effect for pod length; three crosses
viz., KUP 18-350 × Pant U-31 (1.01), KUP 18-345 × T-9 (0.80) and KUP 18-349 × Uttara (0.51) exhibited significant positive SCA effect for seed yield per plant; two crosses
viz., KUP 18-350 × Pant U-31 (1.61) and KUP 18-345 × T-9 (1.51) exhibited significant positive SCA effect for biological yield per plant; two crosses
viz., KUP 18-350 × Pant U-31 (3.64) and KUP 18-345 × Uttara (3.73) exhibited significant positive SCA effect for harvest index. None of the crosses recorded significant positive SCA effects for no. of seeds per pod and 100 seed weight.
The cross with the highest SCA effects for seed yield per plant was KUP 18-350 × Pant U-31. This cross has also shown significant SCA effects in the desirable direction for no. of clusters per plant, no. of pods per cluster, no. of pods per plant, seed yield per plant, biological yield per plant and harvest index. Another important cross combination KUP 18-345 X T-9 showed significant SCA effect in the desired direction for no. of pods per cluster, no. of pods per plant, seed yield per plant and biological yield per plant.
Heterosis
The estimate of heterosis in blackgram is essential to identify the superior hybrids in first-generation. Additionally, the magnitude of heterosis helps to determine genetic diversity and serves as a guide to selecting desirable parents. Both positive and negative heterosis are essential for genetic advancement in crop improvement programs, depending on the breeding objectives. In general, positive heterosis is desirable for yield and most traits, whereas negative heterosis is desirable for earliness.
Out of 15 crosses, ten crosses
viz., KUP 18-350 × Pant U-31 (-4.55), KUP 18-352 × Pant U-31 (-1.82), KUP 18-349 × Pant U-31 (-3.64), KUP 18-345 × Pant U-31 (-4.55), KUP 18-350 × T-9 (-2.73), KUP 18-352 × T-9 (-6.36), KUP 18-350 × Uttara (-3.64), KUP 18-352 × Uttara (-1.82), KUP 18-349 × Uttara (-1.82) and KUP 18-345 × Uttara (-1.82) exhibited significant standard heterosis for days to 50% flowering in the desirable direction.
Five crosses
viz., KUP 18-350 × Pant U-31 (17.24), KUP 18-346 × Pant U-31 (21.64), KUP 18-349 × T-9 (14.17), KUP 18-345 × T-9 (16.04) and KUP 18-346 × Uttara (14.10) exhibited significant positive average heterosis; only one cross, KUP 18-346 × Pant U-31 (19.76) exhibited significant positive heterobeltiosis for number of pods per plant. None of the crosses showed significant heterobeltiosis in the desirable direction for this trait.
Eight crosses
viz., KUP 18-350 ´ Pant U-31 (13.48), KUP 18-346 × Pant U-31 (12.36), KUP 18-349 × Pant U-31 (13.48), KUP 18-350 × T-9 (17.98), KUP 18-346 × T-9 (10.11), KUP 18-349 × T-9 (10.11), KUP 18-350 × Uttara (10.11) and KUP 18-349 × Uttara (16.85) exhibited significant positive standard heterosis for number of seeds per pod.
Six crosses
viz., KUP 18-350 × Pant U-31 (15.26), KUP 18-346 × Pant U-31 (9.89), KUP 18-349 × T-9 (19.25), KUP 18-345 × T-9 (24.87), KUP 18-346 × Uttara (9.42) and KUP 18-345 × Uttara (9.33) exhibited significant positive average heterosis; only one cross, KUP 18-345 × T-9 (13.51) exhibited significant positive heterobeltiosis for seed yield per plant. None of the crosses showed significant heterobeltiosis in the desirable direction for this trait (Table 6).
Thomas et al., (2008), Thamodharan et al., (2016) and
Ram et al., (2013) have found similar kinds of results from their experiment.