Proliferative capacity in relation to metamifop resistance in Echinochloa glabrescens: A case study

Knowing the proliferative capacity of herbicide-resistant weeds is the basis for the integrated management. We collected seeds of two Echinochloa glabrescens Munro ex Hook. f. populations (TS and WH) from rice (Oryza sativa L.) fields in eastern China (F0 populations), and those from individuals surviving the initial metamifop treatment (F1 lines) were tested for their responses to metamifop, and common garden experiments were conducted to compare their productivities. We found that TS was highly resistant to metamifop, and WH was susceptible. After treated with metamifop at the label dose (120 g ai ha-1), averagely 56% and 16% of TS and WH F1 lines contained surviving seedlings, and averagely 24% and 1% F1 seedlings survived among total seedlings of the same population, respectively. After treated with metamifop at a dose of 0, 60, 120 or 240 g ai ha-1, surviving F0 plants escaped from higher doses reproduced higher proportions of metamifop-resistant F1 progenies in both populations. At 120 d after sowing (DAS), TS individuals surviving 2 x label dose of metamifop showed nonsignificant difference in plant heights, biomass and seed production, compared with relative control treatment; while WH plants surviving the label dose of metamifop decreased seed production by 25%-39%. One WH and TS plant individual surviving metamifop treatment at the label dose may generate 10-21 and 490-701 progenies resistant to the label dose of metamifop, respectively.