Tolerance of finger millet to propanil.

Abstract

The slectivity of both foliar-and root-applied propanil was studied among five gramineous plant species. In both applications, finger millet (Eleusine coracana (L.) GAERTN.) showed considerable tolerance to propanil, although it was less tolerant than rice (Oryza sativa (L.) cv. Nihonbare). Large crabgrass (Digitaria ciliaris (RETZ.) KOELER), goose grass (Eleusine indica (L.) GAERTN.) and barnyardgrass (Echinochloa oryzicola VASING.) were found susceptible to propanil. The mechanism of tolerance of finger millet to the herbicide was studied. Metabolic change of 14C-propanil in roots and shoots of rice was much greater than in finger millet and barnyardgrass, and most of the 14C-propanil actually remained unchanged in the latter two plants. Finger millet and barnyardgrass hydrolyzed no propanil at all, while rice did. Substrate specificity of the enzyme was surveyed and only rice plant hydrolyzed propionanilide, propanil and 2, 3-dichloropropionanilide. All three plants have arylacylamidase II activity. Differences in rates of absorption of 14C-propanil by shoots were in the following order: barnyardgrass>rice>finger millet. The rate of translocation of 14C-propanil from roots to shoots of finger millet was comparatively less than that of rice and barnyardgrass.It is concluded that the tolerance of finger millet to propanil is not due to the hydrolytic degradation of the substance, but that the lower accumulation of the chemical in shoots resulting from its lower rate of absorption by the shoots or the lower amount translocated from roots to shoots may contribute to this tolerance.