Seed longevity of red rice ecotypes buried in soil

Abstract

-Red rice is a troublesome weed in irrigated rice production and is spread through contaminated commercial rice seed and machinery. Seed dormancy is a major trait for red rice. Studies were carried out at two locations to determine red rice seed longevity in the soil of several ecotypes from four US states. Five months after burial near Beaumont, Texas only three ecotypes had viable seed (<1%) when buried at 5 cm, but 9 ecotypes had viable seed after two years when buried at 25 cm. At the thirty-sixth month after burial, ecotypes Arkansas 2, Louisiana 2 and 4, Mississippi 4 and Texas 1 had viable seeds, but at less than 1%. Freshly harvested red rice seeds buried at 12 cm near College Station, TX, survived longer than seeds placed on the soil surface. The percentage of maximum viable seeds was 2% for blackhull type Texas 4, after 17 months. In both studies, commercial rice cultivar seeds were not viable after 5 months, regardless of their position in the soil. Under farming conditions with no fallow land preparations or deep tillage, most red rice seed germinated or was dead after 2 to 3 years, with only minor variation among ecotypes.Keywords: red rice, Oryza sativa, rice, seed survival, seed dormancy, strawhull ecotypes, blackhull ecotypes. RESUMO -O arroz-vermelho constitui-se na principal planta daninha infestante de lavouras de arroz irrigado e a sua disseminação ocorre, principalmente, pelo uso de sementes comerciais contaminadas e equipamentos agrícolas. A ocorrência de dormência nas sementes é uma das principais características que dificultam o controle do arroz-vermelho em lavouras. O objetivo deste trabalho foi estimar a longevidade no solo de ecótipos de arroz-vermelho provenientes de diferentes áreas de produção de arroz nos Estados Unidos. O estudo foi conduzido em dois locais: Beaumont e College Station, no estado do Texas (TX). Para sementes enterradas a 5 cm de profundidade em Beaumont, apenas três ecótipos apresentaram sementes viáveis (<1%

Competitive ability of cultivated rice against weedy rice biotypes: A review

“…Furthermore, research showed that secondary dormancy did not occur in both weedy rice and rice cultivars; weedy rice seeds have the ability to survive at low temperatures in winter and afterward re-establish their population. This attribute is said to be ecotype dependent and influenced by other factors, such as burial depth, soil type, climate, moisture, cultivation practices, magnitude of seed production, and dormancy level (Noldin et al, 2006), even though the lower limit temperature for weedy rice germination was the same as for rice (10 °C). Seed dormancy longevity had the advantage of early colonization of rice fields by the weedy rice variant.…”

“…Hence, weedy rice is well adapted to extreme temperatures. Additionally, it can emerge from greater depths than cultivated rice (Noldin et al, 2006). All these attributes account for the ability of weedy rice to compete well with rice cultivars.…”

“…Ratnasekera et al (2013) described the different degrees of rice yield loss related to cultivars, agronomic practice, and interference of approximately 32 weedy rice panicles m -2 with 64% rice yield loss, 12% more root biomass production, and an increase of sterile spikelets in cultivated rice. Noldin et al (2006) found that weedy rice at 4, 16, 25, and 300 plants m -2 caused 20%, 43%, 58%, and 91% yield loss of rice 'Mars'. Cultivated rice yield loss was also reported between 100 and 755 kg ha -1 for every weedy rice plant m -1 in a study conducted in the United States by Ottis et al (2005).…”

Bancos de sementes de plantas daninhas em cultivos de mandioca na Amazônia Central

“…Esse revolvimento pode contribuir tanto para o enterramento de sementes em maiores profundidades quanto para o posicionamento daquelas antes enterradas próximas à superfície. Noldin et al (2006) verificaram que a longevidade de sementes de arroz-vermelho (Oryza sativa) enterradas em camada de solo mais superficial (até 5 cm) foi muito reduzida quando comparada à daquelas enterradas em maior profundidade (12 a 25 cm). Quando as sementes não dormentes retornam à superfície, provavelmente germinam, mas as dormentes poderão retornar para uma profundidade maior, pelo cultivo posterior (Cavers & Benoit, 1989).…”

Weeds occurrence and importance under distinct intercropping systems

“…This indicates that just a few years of distinct management between areas is not enough to promote changes at the soil seed bank in a way that the most problematic weed species are eliminated from the area. However, after a few years the distinct management would probably promote immediate changes at the composition of weed species at the soil surface -species not favored by the management would be present at the soil seed bank but would have to enter in a dormant or quiescent state, waiting for proper conditions for germination (Noldin et al, 2006).…”