Relating rice traits to weed competitiveness and yield: a path analysis

Abstract

Resistance to herbicides in the most important weeds threatens the sustainability of California rice. Weed-competitive rice cultivars could be a low-cost and safe nonchemical addition to an integrated weed management program. Trade-offs between competitiveness and productivity and inconsistent trait expression under weedy and weed-free conditions could complicate the breeding of competitive rice cultivars. A 2-year competition experiment was conducted in the greenhouse involving eight rice cultivars and two weed competition regimes (presence or absence of late watergrass) to examine the effects of rice weed-suppressive ability and tolerance to weed competition (weed tolerance) on rice yield. Competition reduced average rice yield from 32 to 48%, and watergrass biomass from 44 to 77%. Path analysis suggested that enhancing rice weed-suppressive ability and weed tolerance while minimizing possible productivity trade-offs should promote early (12 d after seeding) growth and light-capture traits followed by moderate growth rates before heading and a vigorous grain filling period. Crop growth rate (CGR) after heading was a relevant determinant of yield (direct path: 0.82, P < 0.01) and correlated (r = 0.30, P < 0.01) with weed tolerance. Late biomass accumulation was negatively correlated with harvest index and CGR during ripening (r = −0.46, P < 0.01); thus, late-season competitiveness can lower productivity. Rice traits conferring competitiveness were correlated across weed competition regimes (r = 0.36–0.81, P < 0.01). However, significant cultivar-by-competition and cultivar-by-year interactions suggest that selection efficiency would be greater when traits are identified under competition and in different environments. This study relates to the phenotypic expression of traits for competitiveness. Breeding competitive cultivars will require additional knowledge on trait heritability, genetic correlations with competitiveness, and on the effects of the environment upon gene expression.

Weed Suppression and Tolerance in Winter Oats

“…The contrary is likely to be observed in weed-free conventional farming systems. A strategy for increasing competitive ability while not limiting yield potential in the absence of weeds may focus on enhancing competitive traits such as LAI and vegetative growth early in the year, while limiting competitive traits later in the year, when resources are allocated to grain filling (de Vida et al 2006;Dingkuhn et al 1999). In addition to using cultivars with high tillering ability, increasing sowing rate can more directly increase weed suppression (Korres and Froud-Williams 2002).…”

Competitividade relativa de cultivares de arroz irrigado com Aeschynomene denticulata

“…Determination of competitive interactions between crops and weeds requires appropriate experimental designs and methods of analysis, and the conventional replacement series experiments are the most used to clarify these relationships (Agostinetto et al, 2013;Cralle et al, 2003;Crotser & Witt, 2000;Estorninos et al, 2002;Roush et al, 1989;Vida et al, 2006). In these experiments, the crops generally achieve greater competitive ability than weeds.…”

Interação competitiva de genótipos de arroz e papuã

“…A interpretação dos dados de experimento substitutivo resulta em medida da competitividade entre as espécies, com base na resposta relativa da variável em estudo, podendo ser: produção de massa seca da parte aérea, área foliar, estatura, perfilhamento e índice de cobertura do solo; contudo, a resposta é dada pela variação da proporção de plantas associadas (Cralle et al, 2003;Vida et al, 2006). Em experimentos conduzidos em séries substitutivas, geralmente as culturas demonstram maior habilidade competitiva do que as espécies daninhas.…”