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

Abstract

Weedy rice has been identified as a threat to rice production worldwide. Its phenotypic and genotypic diversity and its potential to compete against rice in all development stages from germination to maturity have resulted in a loss of rice yield and grain quality, which is remarkably high in directseeded rice cultivation. Weedy rice dormancy varies, it has a higher germination rate, and tolerates deeper germination depth compared to rice cultivars. Interactions of weedy rice with cultivars often reflect early vigor, more tillering, nutrient utilization ability for shoot development with respect to rice cultivars even though the latter also show an improvement in shoot development under competition. An exponential relationship has been reported between cultivated rice loss and weedy rice density: this is true for all rice cultivars. The degree of loss is dependent on the competitive ability of the rice cultivar being studied, and each weedy rice biotype also interacts differently. Hence, the need for a comprehensive study of the biology of various weedy rice variants. Difficulties arise in the management of weedy rice due to its physiological, anatomical, and morphological similarities to cultivated rice. The manipulation of the environment to improve cultivated rice production and suppress the emergence of weedy rice variants is important in the management of weedy rice, as well as other cultural practices and use of pesticides. The development of herbicide-resistant rice cultivars is necessary to totally eliminate the weedy rice variants. This review provides information on the competitive ability of weedy rice against rice cultivars; this information is essential to create management options to control weedy rice.

Contrasting patterns of variation in weedy traits and unique crop features in divergent populations of US weedy rice (Oryza sativa sp.) in Arkansas and California

“…54 Weedy rice seeds with long hispid awns could be spread from field to field in California by adherence to hoofstock, wild animals or peoples' clothing. 7 Our results suggest that recently evolved weedy rice in California partitions into ecotypes through selection for awnedness, vegetative growth habit (open canopy) and maturity period (flowering). An abundance of wild/weedy diversity in traits including seed shattering, dormancy and germination 55 , combined with key crop mimic features as an 'adaptive suite' trait combination has the potential to establish weeds in systems with intense weed surveillance.…”

“…Long awns promote segregation with rice straw and chaff at harvest, thereby enhancing seed dispersal and burial in the seedbed . Weedy rice seeds with long hispid awns could be spread from field to field in California by adherence to hoofstock, wild animals or peoples' clothing . Our results suggest that recently evolved weedy rice in California partitions into ecotypes through selection for awnedness, vegetative growth habit (open canopy) and maturity period (flowering).…”

“…In general, weedy rices are more similar to wild relatives in traits such as awnedness, seed shattering (dispersal), rapid growth rate and plant height, tillering, protracted flowering time (heading date), pericarp (bran) pigmentation, seed longevity and dormancy . Weedy traits increase competitive abilities in weeds . Earlier and protracted flowering of weedy rice ensures a wide window for replenishing the soil seed bank.…”

“…[1][2][3][4][5][6] Weedy traits increase competitive abilities in weeds. 3,7,8 Earlier and protracted flowering of weedy rice 8 ensures a wide window for replenishing the soil seed bank. Tall stature and high tillering indicate rapid early growth and high biomass production, which provide a competitive advantage of weedy plants over crop plants.…”

Phylogenetic origin and dispersal pattern of Taiwan weedy rice

“…WRR exhibits rapid plant growth, high levels of seed shattering, and seed dormancy, all of which are traits making it an invasive weed in cultivated rice fields. Because its growth habit and appearance are so similar to that of cultivated rice, once WRR forms a stable population in cultivated fields, controlling it becomes difficult . Consequently, WRR is considered a major problem in global rice production …”