To identify the genotypes, qualitative characters exhibiting stable and discrete inheritance are normally used as plant descriptors. In this study, to characterize the mutant lines, fifteen qualitative characters were used. Among them, there was no variations for the characters such as hypocotyl colour, growth habit, raceme position, attachment of pod to peduncle, immature pod colour, seed shape and hilum colour among the lines. Hence, these traits could not be used to distinguish these mutants. The same report was suggested by
Joshi et al., (2014) in kodo millet land races whcih had erect (62.9%) growth habit and all the land races showed sheath base pigmentation, internode pigmentation, flag leaf at the second primary axis node, panicle exertion and spikelet arrangement on rachis which had no variations among them. This result was similar to the study of
Jayamani et al., (2014) who reported no variation for the characters like corolla colour and lusture on seed surface. The traits
viz., primary leaf colour, terminal leaf colour, leaf pubescence, petiole colour, stem colour, mature pod colour, seed colour and seed lusture showed frequency distribution and thus for identifying the genotypes, these characters might be considered for selection.
Based on 15 qualitative characters, cluster analysis based on similarity matrix and similarity coefficients at 0.75 grouped 40 Urdbean genotypes into 2 clusters. Cluster I had 16 mutant lines along with VBN (Bg) 4 variety and cluster II comprised of 22 mutant lines along with MDU1 variety. From the cluster diagram it was inferred that, morphological features related to MDU1 variety formed one cluster and morphological features related to VBN (Bg) 4 formed another cluster. Among the 40 mutants studied, superior twenty mutants were selected based on single plant yield and biochemical works were carried out on those mutants. Analysis of variance of the seed quality characters
viz., albumin content, globulin content, total soluble protein, arabinose content, hundred seed weight and single plant yield indicated the existence of considerable differences among the mutant lines for those characters (Table 2). This result was supported by the findings of
Veni et al., 2016.
Albumin protein fraction content varied from 6.08 to 8.94 per cent and the mutant line ACM-014-007 recorded the maximum albumin content followed by ACM-014-019 and ACM-014-021. Globulin protein fraction of the mutant lines ranged from 9.81 to 16.39 per cent and the mutant line ACM- 014-021 recorded the maximum globulin content followed by ACM-015-024 and ACM -014-019. Total soluble protein of the mutant lines ranged from 18.31 to 30.14 per cent. The mutant line ACM-015-017 recorded the maximum protein content followed by ACM-014-019 and ACM-014-021.
Arabinose content of the mutant lines ranged from 5.88 to 11.03 per cent. The mutant line ACM-15-023 recorded the maximum arabinose content followed by ACM-015-030 and ACM-015-003 (Table 3). High amount of albumin, globulin total soluble protein content, hundred seed weight and single plant yield was recorded in the line ACM -014-021. More values of albumin, globulin, total soluble protein and hundred seed weight were recorded by ACM-014-019. Albumin content and hundred seed weight were high in the line ACM-014-007. Globulin content, total soluble protein content, arabinose content and hundred seed weight showed high positive association with seed yield per plant. Hence, to improve the battering quality along with yield these characters might be given importance.
Globulin, total soluble protein, arabinose content and hundred seed weight exhibited positive and significant correlation with albumin content. Total soluble protein content exhibited positive and significant correlation with globulin and arabinose content. The results revealed the traits albumin, globulin, total soluble protein, arabinose, hundred seed weight had strong inter correlation with battering quality which might lead to the improvement of battering quality in Urdbean (Table 4). These results were in conformity with finding of
Veni (2015).
Based on the general performance of albumin content, globulin content, total soluble protein, arabinose content, hundred seed weight and single plant yield the mutant lines
viz.,ACM-014-021, ACM-015-015, ACM-15-023, ACM-015-013, ACM-015-003, ACM-015-030, ACM-014-006, ACM-014-007 were identified as the best. Hence to develop high yielding, good battering quality Urdbean varieties, these mutant lines could be utilized directly in the breeding plans. Four mutants
viz., ACM-015-023, ACM-015-030, ACM-015-003, ACM-015-015 with higher arabinose content (higher than 10%) along with two controls were selected and batter volume analysis was assessed. Analysis of variance of the batter volume traits
viz., initial batter volume, final batter volume, increased batter volume, arabinose content and single plant yield exhibited the existence of significant differences among the mutant lines for these characters (Table 5a). The mutant line ACM- 015-030 recorded the maximum final batter volume followed by ACM-015-003 and ACM-015-015. Increased batter volume (IBV) ranged from 79 ml to 120 ml. Maximum protein content was recorded by the mutant line ACM-015-030 followed by ACM-015-003 and ACM-015-015. Arabinose content ranged from 7.38 to 11.03 per cent. Maximum arabinose content was recorded by the mutant line ACM-15-023 followed by ACM-015-030 and ACM-015-003 (Table 5b).
The mutant lines ACM-15-015, ACM-015-030, ACM-015-003, ACM-015-023 were found to be superior based on over all mean performance of important batter volume traits
viz., initial batter volume analysis, final batter volume, increased batter volume, arabinose content and single plant yield. Twenty mutants along with two controls (MDU 1, VBN (Bg) 4) were screened against MYMV to identify the source of resistance by using 1-9 arbitrary scale as per the method suggested by
Alice and Nadarajan (2007). Among them, nine mutant lines have been identified exhibiting promising resistant reaction to MYMV resistance. The mutant lines
viz., ACM-014-021, ACM-015-025, ACM-014-006, ACM-015-022, ACM -015-023, ACM-014-019, ACM-014-007, ACM-015-017, ACM-014- 003 and VBN (Bg) 4 were found to be resistance.
Peerajade et al., 2004, Pathak and Jhamaria, 2004 and
Vanniarajan et al., 2019 also confirmed the results through similar type of genotype evaluations. These mutants could be used directly as a variety or in the breeding plan to generate MYMV resistance or tolerant lines.
In the present investigation, phytic acid content (mg/g), total phenol (mg/g) and total sugar content (mg/g) and MYMV disease score in 20 mutant lines of Urdbean were correlated. It was noted that the Urdbean mutant lines exhibited dissimilar level of total phenol and total sugar content to altering degree of MYMV disease resistance. The highly resistant mutant lines to MYMV
viz., ACM-014-021, ACM-015-025, ACM-014-006, ACM-015-022, ACM -015-023, ACM-014-019, ACM-014-007, ACM-015-017, ACM-014- 003 and VBN (Bg) 4 had reasonably higher total phenol, phytic acid content and lower total sugar content than the susceptible mutant lines (Table 6). In this study, high significant positive correlation was observed between total phenol and phytic acid content (Table 7). Earlier studies reported that resistance to
B. tabaci in had been imparted through higher quantities of total phenols many crops such as cotton (
Balakrishnan, 2006,
Acharya and Singh, 2008) and in brinjal (
Soundarajan and Bhaskaran, 2001).
Sujithra et al., (2012) studied the morphological and biochemical factors influencing plant resistance to pod borer on field bean in 84 entries and the results revealed that tolerant cultivars possessed lower amount of reducing sugars than susceptible cultivars. Like that resistance was imparted due to the presence of higher quantities of phytic acid in crops which was reported by earlier workers
viz.,
Srinivasan and Durairaj (2017) in rice bean, Dhole and Reddy (2016) in 94 green gram germplasm. In resistant lines, resistance was intensified due to the rapid accumulation of phenols and lesser accumulation of total sugar content compared to susceptible ones for this disease. This process rendered a viable approach on plant resistance in insect plant interaction. This mechanism paved a way to understand the biochemical basis responsible for plant resistance to pest and for comparison between resistant and susceptible genotypes for this disease. These findings were supported by the findings of many researchers
viz.,
Acharya and Singh, 2008 in cotton.