Competitive ability of ALS‐inhibitor herbicide‐resistant Fimbristylis miliacea

Abstract

Fimbristylis miliacea, a weed in rice, has evolved resistance to acetolactate synthase (ALS) inhibitors. This study aimed to investigate the competitive abilities of ALS-resistant (R) and ALS-susceptible (S) F. miliacea with rice. A replacement series experiment was conducted in the glasshouse at the Federal University of Pelotas, Brazil. The proportions of rice to F. miliacea were 100:0, 75:25, 50:50, 25:75 and 0:100, with 1060 plants m À2 . The experimental units were arranged in a completely randomised design with four replications. A follow-up study was conducted at the University of Arkansas, Fayetteville, USA, in a split-plot design with four replications. The main plot was species mixture (rice 9 R, rice 9 S, R 9 S). The subplot was competition partitioning (below-and above-ground, below-ground only, above-ground only and no interspecific competition). Leaf area, plant height and shoot dry mass were recorded. Rice was more competitive than the R or S F. miliacea. In equal proportions of rice and F. miliacea, regardless of ecotype, the relative leaf area, height and dry mass of rice were greater than that of F. miliacea. The ALS-resistant ecotype was less competitive with rice than the S ecotype. Intraspecific competition among rice plants was stronger than rice competition with F. miliacea. Competition for below-ground resources was the most critical aspect of interference among rice and F. miliacea. In production fields, high infestation levels of F. miliacea results in significant yield losses; thus, resistance to ALS inhibitors needs to be curtailed.

Pre-Emergent Herbicide Application Performed After Crop Sowing Favors Pigweed (Amaranthus Spp.) and White-Eye (Richardia Brasiliensis) Control in Soybeans

“…This can be explained by the fact that mesotrione is not registered for use as a pre-emergent herbicide in soybeans, suggesting it might lack enough selectivity to this crop to allow for its use. Plant stature is an important trait which dictates the overall outcome of weed-crop competition, as smaller plants might be more easily shaded by large weed plants, affecting light energy capture and photosynthetic activity (SCHAEDLER et al 2015). Average soybean productivity in untreated weed-free checks was increased by 610 kg ha -1 in comparison to untreated control plots (Table 2).…”

Partitioning of Competition for Resources Between Soybean and Corn as Competitor Plant

“…This must have occurred possibly because the F. miliacea plants are shorter than rice plants. Therefore, F. miliacea plants are more impacted by the light competition than the competition for soil resources (Schaedler et al, 2015). In addition, since the root system of F. miliacea shallower, with thinner roots than rice, it may have partially avoided the competition on the rhizosphere.…”

Patterns of resistance to AHAS inhibitors in Limnocharis flava from Malaysia

“…The mutation caused all resistant a. powellii plants to produce thinner roots and stems, and a severe reduction in leaf area and seed production, where as high as 67% resistance cost in aboveground vegetative biomass was observed. Similarly, in a study conducted on AHAS inhibitor-resistant rice weed species, Fimbristylis miliacea (L.) Vahl, it was found that resistant individuals were less competitive with rice than the S plants under the absence of AHAS inhibitors (Schaedler et al 2015). However, it is worth knowing that not all AHAS inhibitor-resistant weeds have conferred fitness disadvantage.…”