The effect of seed dressing pesticides on the symbiotic relationship between rhizobium leguminosarum bv phaseoli and phaseolus vulgaris L.

Abstract

Improvement of bean (Phaseolus vulgaris L.) production requires seed treatment with pesticides for control of pests. In order to maximize nitrogen fixation, inoculation of seed with effective Rh i zob i urn is important. The pesticides may be incompatible with the survival of the inoculated Rh i zob i urn on seed and hence affect symbiotic nitrogen fixation. The study looks at the influence of four chemical seed protectants namely; actellic or pirimophos methyl (0[2-diethylamino]-6-methyl-4-pyrimidinyl 0,0-dimethyl phosphorothioate); aldrin (1, 2, 3, 4, 10, 10-hexach1oro -1, 4, 4a, 5, 8, 8a hexahydo-exo - 1, 4-endo- 5, 8- dimethanonaphtha 1ene); Captan (N-(trich1 oro-methy1thio)-4 cy1ohexene-1, 2 dicarbomixide); and benomyl (Methyl-1- (buty1carbomy1) benzimidazol 2-yl carbamate) on Rh i zob i urn 1egumi nosarum bv phaseo1 i in pure culture, on seed and the subsequent nitrogen fixation. vulgaris L. While captan at 100 ppm was toxic to the Rh i zob i urn in pure culture, benomyl, actellic and aldrin allowed for growth even at 2000 ppm. Captan (25g per kg seed) was more toxic to the Rhizobium on seed leading to a faster decline in population. Benomyl (3.75g per kg seed) was less toxic compared to captan and the control. Aldrin (6.25g per kg seed) and Actellic (4.44g per kg seed) did not influe nee the survival of Rhizobium on seed. None of the pesticides had a significant effect on nodulation, shoot dry weight, total nitrogen and grain yield under both field conditions. Thus in conclusion, under conditions the seed applied pesticides did nodulation and nitrogen fixation in P. vulgar greenhouse and the experimental not i nf1uence is L.