Comparative Analysis of Seed Morphological Traits in Egyptian Cultivated Rice and Weedy Rice

Weedy rice is a conspecific weed of cultivated rice that threatens the production of world rice. The present study aimed to differentiate Egyptian cultivated rice from weedy rice based on seed morphological traits. Seeds from eight cultivated rice varieties and twenty-five weedy rice plants were collected from different paddy fields. The morphological similarity between weedy and cultivated rice, coupled with weedy rice rapid growth, seed dormancy, and shattering, requires efforts to distinguish between them to effectively manage this problematic weed. The seed morphological traits were documented, such as hull, pericarp, and awn color; awn, palea, and lemma length, seed width and length; grain number; and grain weight. A cladistic analysis was performed using these traits. Notable variations in seed morphology were observed between cultivated and weedy rice. Cultivated rice seeds exhibit straw-colored hulls, white pericarps, and lack awns, whereas most weedy rice seeds have brown hulls, red-brown pericarps, and either short or long awns. The presence of awns and the high seed length-to-width ratio in most weedy rice can be considered adaptive mechanisms, facilitating seed dispersal. Cultivated rice generally has a higher grain weight than weedy rice, reflecting the better endosperm development, which results in greater grain mass. Understanding these morphological variations can used by farmers for early identification and removal to prevent seed dispersal and control weedy rice. The analysis of the cladogram, which focused on seed morphology, demonstrated a significant relationship between cultivated and weedy rice, suggesting a shared genetic basis and possibly originating from a common ancestry.