Evaluation of germination and seedling tolerance index of black gram genotypes in response to herbicide glyphosate

Abstract

Herbicides are expected to protect crop plants from weed competition without harming the crop plants. Glyphosate (N-[Phosphonomethyl] glycine) is a non selective systemic herbicide used for control of annual and perennial plants including grasses, sedges, broad leaved weeds and woody plants. But broad spectrum herbicides like glyphosate can also damage non target plants. Black gram is one such target crop and therefore it becomes necessary to select ideal blackgram genotypes, which may be tolerant to herbicide stress and produce substantial yield under stress conditions. Herbicide tolerance of six black gram genotypes was investigated at the germination and seedling growth stages. Seed germination percentage, survival percentage, seedling root length, seedling fresh and dry weight, seedling vigour index and tolerance index was assessed after 7 and 15 days of herbicide treatment. Results showed that increasing glyphosate concentrations caused reduction in all the studied parameters of seedlings in all the genotypes but response was different among genotypes. Root length inhibition was more pronounced than shoot length inhibition and thus can also be chosen as selection criteria for screening of tolerant and susceptible genotypes. Decrease in root length was maximum in Azad-2 and PU-31 than the other four genotypes indicating their lowest tolerance to glyphosate. Tolerance index was highest for PU-19, IPU-94-1 and lowest for PU-31 and Azad-2. More vigorous cultivars like PU-19, Azad-2 and IPU-94-1 could be considered as plant materials useful for future development of herbicide tolerant cultivars in plant breeding.