Seed morpho-physiological trait diversity and its association with herbicide resistance in Alabama Italian ryegrass ( Lolium perenne L. ssp. multiflorum ) populations

Wide diversity in plant adaptive traits, such as seed size and dormancy, is generally linked to the rapid spread, invasiveness and adaptative potential of a weed species. Italian ryegrass [ Lolium perenne L. ssp. multiflorum (Lam.) Husnot] is a significant weed species in winter crops such as wheat ( Triticum aestivum L.) and summer crops such as corn ( Zea mays L.), soybean [ Glycine max (L.) Merr.], and peanut ( Arachis hypogaea L.) in Alabama. In this study, diversity in seed morpho-physiological traits–such as seed length, awn length, seedling length, 100-seed weight, and seed dormancy was assessed in 65 L. multiflorum ssp. multiflorum populations collected from Alabama in 2023. Significant diversity was observed among the populations for 100-seed weight (61.8-295.8 mg), seed length (3.5-6.43 mm), awn length (0-7 mm), and seedling length (0.5-38.6 cm). Germination speed was significantly lower in the populations with high initial seed dormancy (>30%) compared to medium (15-30%) and low dormancy groups (<15%) at 0 and 3 months after harvesting. Additionally, the relationship between herbicide resistance status and seed morpho-physiological traits in these populations was explored. A significant positive association was observed between seed dormancy and the number of survivors following glyphosate ( P < 0.01) and clethodim ( P < 0.01) treatments. The observed diversity in morpho-physiological traits could be the reason of enhanced adaptability of L. multiflorum ssp. multiflorum , and its correlation with herbicide resistance indicates directional selection or co-existence of specific seed morpho-physiological traits with herbicide resistance under the repeated use of similar modes of action.