EFFECTS OF SEED-BORNE MICRODOCHIUM-NIVALE ON ESTABLISHMENT AND GRAIN-YIELD OF WINTER-SOWN WHEAT

The relationship between seed-borne levels of Microdochium nivale and establishment, development and subsequent grain yield of winter-sown w heat under field conditions was quantified. Nine samples of different varieties of wheat were sown in a field trial at two seeding rates (40 0 seeds and 480 seeds m(-2)) using untreated seed in November 1991. Pl ant establishment in January 1992 was variable between varieties and r anged from 26% to 69%. Samples of seed from each variety were tested o n potato dextrose agar and found to have levels of M. nivale ranging f rom 6% to 79% significantly correlated with plant establishment. Labor atory work showed seed-borne M. nivale was effectively transmitted to seedlings. At harvest, total grain yield ranged from 5.6 t ha(-1) to 9 .4 t ha(-1) and was significantly correlated with establishment; the n umber of ears m(-2) (427 to 629) was also significantly correlated wit h establishment. Observed reductions in emergence and grain yield indi cate the importance of effective control of seed-borne M. nivale infec tion in winter wheat.