Suppression of Junglerice [Echinochloa colona (L.) Link] by Irrigated Rice Cultivars in Latin America

Abstract

Continuous rice (Oryza sativa L.) cropping in Latin America and the Caribbean has resulted in serious weed problems and herbicide overuse. Competitive rice cultivars could help reduce herbicide dependence. A study was conducted during 1994 and 1995 at Palmira, Colombia, to (i) assess the competitiveness of semidwarf irrigated rice plant types adapted to Latin America and the Caribbean's direct‐seeding systems, (ii) identify plant traits responsible for such competitiveness, and (iii) detect adverse effects of competitiveness on rice yield potential. Pregerminated seed of 10 and 14 semidwarf rice cultivars was sown on drained puddled soil in 1994 and 1995, respectively. Cultivars were grown weed‐free or with junglerice [Echinochloa colona (L.) Link] (40 viable seeds m−2, broadcast immediately after seeding rice), and were intermittently irrigated to keep the soil near saturation. Rice and junglerice biomass, leaf area index, tiller number, and height were recorded at 20, 40, 60, 90, and 120 days after emergence (DAE). Rice cultivars differed in their competitiveness against junglerice. Average yield losses ranged from 27 to 62% under saturating junglerice infestations of up to 5.9 Mg DM ha−1. Leaf area index, tiller number, and canopy light interception recorded in competition, and not much before 40 DAE, correlated positively with rice competitiveness. Competitive semidwarf cultivars can substantially reduce the number of herbicide applications in systems where suboptimal water control does not allow weed suppression by flooding. Breeding to enhance rice competitiveness appears as a valid objective, since competitive and also highly productive cultivars were identified in this study.

Competitividade relativa entre cultivares de arroz irrigado e biótipo de capim-Arroz (Echinochloa spp.)

“…Esses resultados permitem inferir que não há efeito acentuado de características intrínsecas de cultivar sobre o capim-arroz e que a habilidade daqueles em interferir sobre a planta daninha foi equivalente. Os resultados observados discordam dos encontrados por Fischer et al (1997), Fleck et al (2004) e Galon et al, (2007a), os quais afirmaram a existência de variabilidade competitiva de acordo com o ciclo de desenvolvimento de cada cultivar. Contudo, isso pode decorrer do fato de que nos trabalhos desenvolvidos em campo tem-se a influência de fatores bióticos e abióticos e que isso pode atuar de maneira diferenciada para cada cultivar; assim, tem-se uma maior importância da variação do ciclo de desenvolvimento e da estatura de plantas, o que não se observa em casa de vegetação, em razão de o ambiente ser controlado e de haver menor pressão por parte dos fatores bióticos e abióticos.…”

Competitividade de cultivares de arroz irrigado com cultivar simuladora de arroz-vermelho

“…Contudo, aparentemente a estatura de planta não tem sido um parâmetro convenientemente selecionado para aumentar a capacidade competitiva do arroz, o que seria importante, principalmente quando as infestantes possuírem baixa estatura (Fischer et al, 1997).…”

“…Mas a capacidade de cobertura do solo depende, além da estatura de planta, da área foliar e do ângulo das folhas (Fischer et al, 1997).…”

Performance of Newly Developed Weed-Competitive Rice Cultivars under Lowland and Upland Weedy Conditions

“…However, the result for the 2013 WS showed that taller plants will not necessarily give higher grain yield. Fischer et al (1997Fischer et al ( , 2001) reported that there is no clear association between plant height and weed-suppressive ability in irrigated and upland rice. Similarly, having higher leaf chlorophyll content (SPAD reading) and longer panicles is not associated with grain yield.…”