Competition Indicator in Alfalfa Populations Following Recurrent Selection to Glyphosate Tolerance

Abstract

The bad cide in adopting cide-tolerant alfalfa cultivar is the shift in weed communities with rise proportion of tolerant species. The main objective of the recent study was to trace competition indicator of alfalfa populations as affected by recurrent selection to glyphosate tolerance. Two cycles of recurrent selection for Glyphosate tolerance were imposed on each base population. Competition indicators following selection included plant characters and weed bioassay. In most studied populations, plant height decreased with the first cycle of selection to glyphosate tolerance by -8.991, -3.225, -1.240 and -0.426% in Siwa, Hasawi, C.U.F101 and Baladi1 populations, respectively. Except for, Sirivar population an increase by +6.740 % was accompanied with selection to glyphosate tolerance. On the other hand, by cycle two of selection, populations had different response relative to C1, where Baladi1, C.U.F101 and Sirivar populations had a decrease in plant height with values reached -1.761, -0.720 and 0.617 cm, respectively. While, Hasawi and Siwa populations showed an increased plant height by +3.816 and +3.197cm, respectively. Glyphosate treated plots (+ and -) were evaluated by weed bioassay in terms of green and dry weight during a course of three successive cuttings. Exposed genetic materials to glyphosate treatments were selection cycles (C0, C1 and C2) of the five studied populations.The first cycle of selection to glyphosate tolerance expressed a significant increase of 9.59 and 10.93% relative to the base population as green and dry weed weights, when evaluated under glyphosate treating condition. The second cycle of selection was associated with a reduction of 29.63 and 28.88% in green and dry weight of weed. This might indicate a proliferation of alfalfa plants that were selected for glyphosate tolerance, the matter that reduced the mass of weeds, whether, as green or dry weight.