The potential for selecting wheat varieties strongly competitive against weeds

Abstract

The cotiipet(ti.ve abilities of a wide range of genotypes of wheat {Trilicwnaestivum L.) and durum wheat {Triticum durum Desf.) against Lolium rigidunt Gatud. (annual ryegrassj were examined lo determine the potential for breeders to select strongly competiti-ve varieties. Considerable potential within the wheat genonie to hreed varieties with greater competitive ability was demonstrated. In 1993. 250 genotypes from aroimd the world were screened and in 1994 st subset of 45 (mainly Australian) genotypes were further examined. A uniform deasity of L. rigidum reduced grain peld of wheat by up to about 80% in 1993 and to 50% in 1994, depending on wheat genotype. Reduction in grain yield was correlated with i. rigidum dry matter. Wheats varied in competitive ability with source, and durum wheats were less competiifive than T. aestivum. The old' standard wheat varieties (released between 1880 and 1950) suppressed the weed more than all the current varieties, with the exception of eight Fi hybrids. A doubling of the crop seeding rate of 10 of the genotypes in 1994 reduced the biomass of L. rigidum by an average of 25% compared with the standard seeding rate. Ranking of competitive ability of varieties at high deosity was consistent at both seeding rates. The strongly competitive genotypes had high early biomass accumulation, large numbers of tillers, and were taU with extensive leaf display. The potential for breeding enhanced competitive ability in wheat is discussed.

Wheat Yield and Weedness under Different Rate of Nitrogen Fertilization

“…Time of sowing and density (Walter et al, 2002) of wheat is important for tillering, enough to suppress weed in spring season and reduce yield losses caused by late sowing, low temperature during winter and early spring time. Wheat density can influence the reduction of weed dry matter more than 60% (Lemerle et al, 1996) and reduction to weed structure (Korres & Froud-Williams, 2002). The application of herbicides do not influence the wheat density and wheat yield (Kristensen et al, 2008).…”

“…Adequate wheat growing contributes to competitiveness with weed. Crop shading ability contributes to weed control by decreasing chemical application and environmental protection (Lemerle et al, 1996). Increase in wheat density and uniformity can help in suppression of weeds (Olsen et al, 2006).…”

Associação de características de planta em cultivares de aveia com habilidade competitiva

“…Dificilmente uma única característica morfológica conferirá elevado potencial competitivo às plantas de um cultivar (Lemerle et al, 1996). Assim, o cultivar UPFA 22 destacou-se positivamente, englobando várias caracterís-ticas favoráveis à habilidade competitiva, que lhe conferiram, neste estudo, poder de suprimir os competidores, enquanto para URS 22 se verificou o contrário.…”

“…Existe um potencial elevado para criação de novos cultivares que apresentem habilidade competitiva superior, reduzindo, dessa maneira, a dependência aos herbicidas (Lemerle et al, 1996).…”

Características de plantas de soja que conferem habilidade competitiva com plantas daninhas

“…As características morfológicas que estão mais diretamente relacionadas à HC superior da cultura são: matéria seca da parte aérea (WORTMANN, 1993;OLESEN et al, 2004), estatura (FLECK, 1980;MCDONALD, 2003), tamanho das folhas (WORTMANN, 1993;LEMERLE et al, 1996); índice de área foliar (GIBSON et al, 2003;HAEFELE et al, 2004), cobertura do solo (CALLAWAY, 1992;BALBINOT JUNIOR. et al, 2003) e densidade foliar na parte superior da planta (BEGNA et al, 2001;CATON et al, 2001).…”