Allelopathic Effects on Germination and Seedling Growth of Clovers by Endophyte‐Free and ‐Infected Tall Fescue

Abstract

Reports of allelopathy by tall fescue (Festucarundinacea Schreb.) on Trifolium species are inconsistent. Many tall fescue plants are infected with a fungal endophyte (Acremonium coenophialum Morgan‐Jones & Gams), which may account for some of the inconsistencies. My objective was to investigate the allelopathic effect of extracts of endophyte‐free (TF − E) and ‐infected (TF + E) tall fescue seeds the seed germination and seedling growth (shoot, root, and root‐hair length and root‐hair density) of five Trifolium species (ball clover, T. nigrescens Viv.; crimson clover, T. incarnatum L.; red clover, T. pratense L.; subterranean clover, T. subterraneum L.; and white clover, T. repens L.). Extracts were prepared by passing 50 g of seed through a pulverizing mill, soaking the milled seed in 500 mL of deionized water, filtering, and sterilizing the solution. Differences among allelopathic effects for seed germination were attributed to legume species. Although the presence of fungal endophyte had no effect on seed germination, germination of ball, crimson, and red clover seed was significantly reduced in extracts of tall fescue seed. Differences among allelopathic effects for shoot and root lengths were attributed to legume species. Seedling shoot length was significantly increased and root length was significantly decreased for clover seedlings grown in tall fescue extracts. Differences among allelopathic effects for root‐hair length and density were attributed to species and substrate (TF − E vs. TF + E) differences. There was a 34% reduction in root‐hair length and a 45% reduction in root‐hair density for clover seedlings grown in seed extracts compared with seedlings grown in water. Seed germination and seedling shoot and root lengths inadequately expressed the subtle allelopathic effects of the fungal endophyte. Micromorphological characters, such as root hairs, may be more sensitive in detecting allelopathic effects.