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.

No abstract

El desarrollo de la biotecnología aplicada a los cultivos ha generado fuertes debates éticos y sociales sobre su uso. El presente estudio tuvo por objetivo revisar las evidencias epidemiológicas existentes relacionando el consumo de alimentos genéticamente modificados, en particular aquellos provenientes de cultivos con resistencia a algunos insectos plagas en los que se han introducido proteínas Cry aisladas de Bacillum thurigiensis con probables daños o trastornos en la salud de las personas. Se realizó una revisión en profundidad en el periodo 2007 a 2019, en bases de datos. Se excluyeron aquellos artículos que no hacían referencia a salud humana. Se obtuvieron 1 350 y finalmente se revisaron 118. La revisión permitió concluir que la mayoría de los estudios existentes se centran en información respecto a la composición química y ensayos in vitro o en laboratorio con animales. Igualmente, que el principio rector de equivalencia sustancial hoy utilizado en forma generalizada para la evaluación de potenciales efectos en salud, no debería sustituir la necesidad de una evaluación rigurosa de los productos incluyendo ensayos nutricionales, inmunológicos y toxicológicos. Por último se comprueba también que la evidencia epidemiológica incluida es insuficiente por lo que lo que no es posible concluir a partir de ella, sobre la inocuidad de estos alimentos.

Pesticides have become an essential input for agriculture in the last decades. However, the growing concern about the potential impact produced by such dependency on human health and the environmental level has led to strong questionings about the use of pesticides worldwide. This paper aims to analyze the use of pesticides in Uruguay's agriculture and their potential risks with an emphasis on ecotoxicological risks. For such purposes, data on imports and use of pesticides in Uruguay and some other agricultural regions corresponding to the last two decades (2000-2020) were collected. In addition, information on the risks associated with the use of different pesticides compiled in the Pesticide Properties Database of the University of Hertfordshire was reviewed, as well as information generated by related national and international research. The information collected indicates high intensity usage of pesticides in Uruguayan agriculture and uncertainties in relation to environmental risks that may arise from the current forms of use.