Assessing Physiological and Genetic Evidence for Evolution of Shared Weedy Rice Traits at the Vegetative Growth Stage

Abstract

Weedy rice (Oryza spp.) has successfully adapted to invasion of cultivated rice (O. sativa L.) fields by being a strong competitor from the early vegetative growth stages to crop harvest. While seed shattering and seed dormancy have been shown to contribute to competitiveness at the reproductive stage, much less is known about the traits that could contribute to weedy rice adaptation at the vegetative stage. We examined several growth and physiological traits in five different weedy rice lineages with different ancestral origins, and found that no single vegetative phenotype characterizes all weedy rice. Divergence in growth and physiological traits between weedy rice groups and their putative cultivated ancestors has been limited, suggesting that altered vegetative traits have not been a common path to weed adaptation. There is a lack of convergence in patterns of gene expression in two independent weedy rice lineages, suggesting that there are few shared genetic mechanisms in the evolution of vegetative traits. We conclude that it must not be assumed that all weedy rice groups necessarily have altered vegetative growth or physiological mechanisms compared to their ancestors, that facilitate their invasion of crop fields.

A derived weedy rice × ancestral cultivar cross identifies evolutionarily relevant weediness QTLs

“…Seed shattering is an important trait that consistently distinguishes cultivated and weedy rice with high seed shattering being prevalent in weedy rice populations (Huang et al., 2021; Thurber et al., 2010). We identified seed shattering QTLs in multiple chromosomes (Table 1), indicating that there are numerous mutational targets that can affect this trait in rice.…”

“…Flowering simultaneously as the crop can also be beneficial to weeds in some circumstances, as a way to avoid conspicuousness in the fields or to achieve dispersal by contaminating seed stocks (Ellstrand et al., 2010). And seed dispersal, known as seed shattering in the grasses, is a trait that most consistently differentiates weedy from cultivated rice (Huang et al., 2021; Thurber et al., 2010; Ziska et al., 2015) and helps weedy rice disperse and increases its presence in the seed bank.…”

Multiple compensatory mutations contribute to the de‐domestication of Iberian weedy rice

“…Among the most iconic weedy rice traits shared by multiple weedy rice populations around the world are seed shattering and a red pericarp (Huang et al, 2021). Both traits confer clear advantages for a weedy lifestyle.…”

Experimental methods for phenotypic and molecular analyses of seed shattering in cultivated and weedy rice

“…Recognized by its red pericarp, leading to the term "red rice," weedy rice often exhibits distinct traits such as black, brown or straw-colored hulls, awned seeds, and taller plants; however, these features are not universal across all weedy rice populations (Huang et al, 2021;Roma-Burgos et al, 2021). Historically, weedy rice plants have often been taller than rice cultivars (Schwanke et al, 2008;Shivrain et al, 2010), but the introgression of genes from cultivars and selection pressure through hand weeding select for plants mimicking rice cultivars (Burgos et al, 2014;Piveta et al, Abstract: The seed shattering trait has been repeatedly reshaped during rice evolution.…”