Effects of Co-inoculation with Pratylenchus thornei and Fusarium culmorum on Growth and Yield of Winter Wheat.

Growth and yield of winter wheat are suppressed by Pratylenchus thornei and by Fusarium culmorum. Many fields in cereal production regions throughout the world are infested by both pathogens. We evaluated effects of one or both pathogens on winter wheat growth, grain yield, and disease parameters at heading and harvest stages over 2 years in inoculated, rainfed pots incubated outdoors. P. thornei nematodes were inoculated at 1, 2, or 4 nematodes/g of soil and F. culmorum was added as colonized millet seed at 0.65 g/kg of soil. At harvest, compared with the noninoculated control, the high rate of P. thornei reduced (P < 0.05) plant height, shoot weight, root weight, and grain yield by 19, 17, 48, and 31%, respectively. F. culmorum alone reduced these parameters by 15, 16, 22, and 22%, respectively. Co-inoculations caused reductions of 27, 38, 61, and 63%, respectively. The reproductive rate of P. thornei was not greatly affected by co-inoculation with F. culmorum. Disease severity ratings at both plant growth stages became amplified as the nematode density was increased, and were much greater in the presence of both pathogens. Effects of co-inoculation on grain yield were slightly greater than predicted by additive effects of the individual pathogens, suggesting a synergistic effect on yield depression.