Weedy rice in sustainable rice production. A review

Abstract

Weedy rice refers to the unwanted plants of the genus Oryza that have some undesirable agronomic traits and pose a major threat to sustainable rice production worldwide. Widespread adoption of direct seeded rice and hybridization or gene flow between cultivated rice and their wild relatives has resulted in the creation and dissemination of weedy rice. Currently, weedy rice (Oryza sativa f. spontanea) has become one of the most common weeds infesting rice fields worldwide. In this paper, we review the biology, physiology, evolution, and genetic features of weedy rice. We also discuss the major obstacles in weedy rice management, including high diversity of weedy rice, ecological impacts of gene flow on weedy rice, changing climate, and weedy rice management. We then present a framework for the sustainable management and utilization of weedy rice. Our main emphasis is to explore the reservoir of natural variations in weedy germplasm and to utilize them for crop improvement. This review outlines some of the latest biotechnological tools to dissect the genetic backgrounds of several favorable traits of weedy rice that may prove beneficial for breeding and evolutionary studies on cultivated rice. We suggest that by merging the disciplines of genomics, breeding, and weed management, we can achieve the goal of sustainable rice production.

Gene drive systems: do they have a place in agricultural weed management?

“…If these genes could be driven through populations, they may reduce weed competitive ability. Similarly, studies in weedy rice have begun to unravel the genetic basis of the evolved seed dormancy and seed‐shattering traits that contribute to the persistence and spread of wild rice, providing another molecular target for efforts to reduce the fitness of weeds in agroecosystems . Efforts could also be directed towards meiotic drive systems that bias the sex ratio in dioecious weedy species such as Amaranthus spp., leading to biased sex ratios.…”

“…Similarly, studies in weedy rice have begun to unravel the genetic basis of the evolved seed dormancy and seed-shattering traits that contribute to the persistence and spread of wild rice, providing another molecular target for efforts to reduce the fitness of weeds in agroecosystems. 39 Efforts could also be directed towards meiotic drive systems that bias the sex ratio in dioecious weedy species such as Amaranthus spp., leading to biased sex ratios. Other attempts to target plant reproduction and fecundity might focus on genetic manipulations that interfere with, for example, gametogenesis to limit pollen or ovule production, leading to reductions and/or biases in gamete production.…”

Phylogenetic origin and dispersal pattern of Taiwan weedy rice

“…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 …”

“…Traditionally, rice is grown in flooded fields that are sown through transplanting; a method which provides some WRR control in infested fields. In Japan, where a transplant system is implemented, a density of five WRR plants per m reduces rice production by 10% . Furthermore, WRR damages rice production more than another major weed of rice, barnyardgrass ( Echinochloa crus‐galli ), with just one to three WWR plants reducing production to equivalent levels of five to 10 barnyardgrass plants .…”

“…1 Consequently, WRR is considered a major problem in global rice production. 2,3 There are various hypotheses pertaining to the evolutionary origins of WRR that have been proposed. 4 Some WRR occurs in rice production areas where wild relatives (e.g.…”