In the present study, data recorded on seed germination were presented in Table 1. A gradual decrease in seed germination with increasing concentrations of mutagens was observed in both the varieties of lentil. However, the extent of decrease in seed germination differed with respect to the mutagens as well as the varieties. Seed germination was affected more adversely in the variety Type-8 than Pant L-406. In Type-8, the percentage inhibition was 12.37 and 32.98 with 0.01% and 0.04% SA, respectively. However, it was 6.31% and 23.16% with the same concentrations in Pant L-406. Sodium azide treatments were found to cause maximum reduction in seed germination as compared to HZ and EMS treatments.
Reduction in germination by mutagenic treatments could be due to delay or inhibition of physiological and biological processes including enzymatic activity
(Kurobane et al., 1979), imbalances of hormones (
Chrispeels and Varner, 1967) and hampering of mitotic processes
(Ananthaswamy et al., 1971). Usuf and Nair (1974) stated that gamma irradiation accelerated the degradation of existing enzymes involved in the formation of auxins, thus reduces the seed germination. High reduction in germination percentage in SA treatments may be due to weakening and disturbances of growth processes. Greater lethality at higher mutagenic concentrations was observed in both the varieties. The larger sensitivity at higher doses of mutagens has been attributed to various factors such as change in the metabolic activity of the cells and imbalance between the promoters and inhibitors of growth regulators (
Natarajan and Shiva Shankar, 1965;
Meherchandani, 1975). In M
2 generation, although a dose dependent decrease in seed germination persisted, however the percentage inhibition in seed germination was less and showed a good proportion of recovery as compared to M
1 generation.
Data recorded for seedling height of 10 days old seedlings raised in petri-plates were presented in Table 2. The results showed that all the mutagenic treatments brought dose dependent reduction in seedling height. In Pant L-406, the total seedling height was 11.40 cm in control. Seedling injury ranged from 4.38 to 21.66 per cent in EMS treatments, whereas it ranged from 6.66 to 26.93 percent in HZ treatments. The injury was more drastic in SA treatments ranging from 9.12 to 31.14 per cent. In Type-8, the seedling height was 11.85 cm in control. Seedling injury ranged from 13.92 to 37.55 percent with 0.01% to 0.04% treatments of SA. Compared to M
1 in both the varieties, the percentage injury in seedling height was reduced to a large extent in M
2 generation. The reduction in seedling height after mutagenic treatments is mainly due to the uneven damage caused to the meristematic cells resulting from genetic injury. Variation in auxin level (
Goud and Nayar, 1968) and changes in the specific activity of enzymes
(Cherry et al., 1962) were correlated with reduction in seedling height after mutagenic treatments.
Studies of pollen fertility in mutagen treated population forms a reliable index in assessing any internal change in the plants as well as in determining the efficiency of a particular mutagen. The pollen fertility was dose dependent as evident from proportionate decrease with increasing concentrations of EMS, HZ and SA in both the varieties of lentil (Table 1). The dose dependent decrease in pollen fertility was earlier reported in
Nigella sativa (
Mitra and Bhowmik, 1998),
Gossypium hirsutum (
Muthusamy and Jayabalan, 2002),
Cicer arietinum (Barshile et al., 2006), Vigna radiata (
Khan and Wani, 2006) and
Vigna mungo (Sharma et al., 2006; Bhosale et al., 2013). The highest percentage of reduction 27.10 and 23.38 in pollen fertility was observed with 0.4% of EMS and 0.04% of HZ treatments in Pant L-406, whereas in Type-8, it was 27.70 and 24.00 percent with the highest concentration of EMS and HZ, respectively. Among the various mutagens, EMS caused more drastic effects on pollen fertility than the other two mutagens. In majority of the cases, meiotic abnormalities are responsible for pollen sterility (
Gaul, 1970;
Sinha and Godward, 1972;
Gottschalk and Klein, 1976;
Kumar and Singh, 2003). The sterility induced by SA seems to be more genic and less chromosomal. Reduction in pollen fertility in M
2 generation was fairly less as compared to M
1 generation, indicating that recovery mechanism had operated in the intervening generations.