Effect Of Soybean Mosaic On Component Yields From Blends Of Mosaic Resistant And Susceptible Soybeans

To gain information on how yield reductions are generated by soybean mosaic under field conditions, experiments were conducted during four seasons to study the competition, as reflected in seed yield, between healthy and mosaic‐infected soybean [ Glycine max (L.) Merr.] plants. Three pairs of closely related soybean mosaic virus (SMV)‐ resistant (R) and ‐susceptible (S) sibling soybean lines were planted in blends of 10, 20, 40, 60, and 80% R and complementary S seed. Natural virus sources were present at one location, and at the other location a virus source was provided for aphid transmission into the plots. Using total yields, plant stand counts during August or September, and the R or S reaction of seedlings grown from seed harvested from each plot, average yields per R and S plant were calculated for each blend. Yields per R plant generally increased as the percentage of R plants in the blend decreased, whereas yields per S plant varied only slightly among the various blends. Total yields generally increased with increasing percentages of R plants; however, this yield varied among seasons, locations, and sibling lines. The line with ‘Semmes’ as the recurrent susceptible parent manifested the greatest yield response. Yield compensation by nonlnfected soybean plants in fields with mosaic probably plays a major role in moderating yield loss.