Use of 1,8-naphthalic anhydride to improve grain sorghum tolerance to alachlor

Abstract

The relative tolerance of selected inbred lines and hybrids of grain shorghum [Sorghum bicolor (L.) Moench] to alachlor [2-chloro2',6'diethyl-N-(methoxymethyl)acetanilide] was evaluated in greenhouse bioassays. Grain sorghum hybrids generally were more tolerant of alachlor than parental lines. The female line 'ATx399' (Wheatland) was the most susceptible of the grain sorghums studied. The hybrid combination of 'ATx3197 x Tx414' (RS 626) was more tolerant of alachlor than any other line or hybrid. The effectiveness of 1,8-naphthalic anhydride (hereinafter referred to as NA) and other possible seed treatments for altering the tolerance of 'ATx399' to alachlor was evaluated with germination bioassays. The recommended rate (0.5% w/w) of NA caused 14 and 18% reductions in shoot and root length, respectively, when treated seed were assayed in distilled water. However, when assayed in 16 ppmw of alachlor, shoot length attained by NA-treated seed was equal to 63% of check compared to 34% for untreated seed. Activated carbon at rates to 4.0% (w/w) of 'ATx399' grain sorghum seed did not improve its tolerance of alachlor. Seed treatment with 0.001 N HCl (hydrochloric acid) for 12-hr period provided protection equal to that obtained with NA. GA (gibberellic acid) seed treatments increased shoot length to mask part of the growth reduction caused by alachlor but the coleoptile and first leaf of the GA-treated seedlings did not expand normally. ...