RESEARCH-PGR: Characterizing the Genomic Basis of Weedy Rice Competitiveness

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Weeds that infest crop fields are a primary factor limiting global agricultural productivity in the United States and globally. One of the most problematic weeds for rice production is weedy rice (Oryza sativa), a close relative of cultivated rice that infests rice fields and aggressively outcompetes crop cultivars. This research seeks to understand and characterize the genetic basis and origins of the traits that allow weedy rice to invade rice fields, reduce yields and contaminate harvests. Three key features of weedy rice growth and reproduction will be characterized: patterns of root system growth that allow the weed to outcompete rice for soil nutrients; the genetic and developmental basis of seed dispersal mechanisms that allow the weed to rapidly invade and proliferate in rice fields; and the differential resilience shown by the weed against rice blast, a common fungal disease of rice fields. In addition to providing key insights into the basis of competitiveness in weedy rice, the project will provide genetic resources to the rice research community, training opportunities for K-12 science teachers, and educational training experiences for students including hearing-disabled students, a minority group that is underrepresented in STEM careers.Weedy rice (Oryza sativa) is an aggressive weed of rice production areas worldwide. It has evolved multiple times independently through a process of 'de-domestication' (feralization) from cultivated rice. As such, this system provides a natural replicated experiment for studying the genetic mechanisms that underlie weediness traits and the extent to which these are constrained by genetic background. Prior work by the collaborating research team has established that weedy rice aggressively outcompetes its cultivated relatives due, in part, to three key features: altered root system architecture (critical for below-ground resource acquisition), highly shattering seed (conferring differential reproductive success and dispersal ability), and differential pathogen resistance (permitting a competitive advantage in US crop fields). This project will characterize each of these features of weedy rice competitiveness, with the following specific goals: 1) to determine the genetic basis of the root system architecture (RSA) that has evolved convergently with repeated origins of weedy rice, and establish the connection between weedy rice RSA and weed competition via differential nutrient uptake; 2) to identify the genetic basis of seed shattering in independently-evolved populations of weedy rice, and establish the mechanisms underlying the evolutionary lability of this trait; and, 3) to determine the genetic and biochemical bases underlying the differential resilience of US weedy rice to rice blast disease, a major fungal pathogen of rice. Beyond providing insights for the research community, the project will also benefit stakeholders, STEM educators and students through the production and dissemination of genetic and educational resources targeting groups underrepresented in STEM careers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.