Source of resistance aff ect soybean yield, yield components, and biomass accumulation in Heterodera glycines-infested fields

The soybean cyst nematode (Heterodera glycines Ichinohe) is the main yield limiting pathogen of soybean [Glycine max (L.) Merr.] in the USA. Resistant cultivars are the most efficient management tool today. Our research studied the physiological basis of yield differences between H. glycines-susceptible and H. glycines- resistant cultivars developed from the Hartwig, PI 88788, and Peking sources of resistance at two locations in Iowa during 2005 and 2006. Supplementing resistance with chemical control may improve soybean yield and/or nematode control, so nematicide application {aldicarb[2-methyl-2 (methylthio) propionaldehyde O-(methylcarbamoyl) oxime]} was included as an experimental factor. Aldicarb increased total plant biomass by 9% during R1-R5 soybean growth stages, but there was no increase in seed yield. Yields of the resistant cultivars were greater than those of the susceptible cultivars, except for the Peking source. Compared with the susceptible cultivars, cultivars with H. glycines resistance from PI 88788 had a 13% increase in yield associated with a 15% increase in growth during R1-R5. In cultivars with resistance from Hartwig, a 6% increase in yield was associated with a 4% increase in R1-R5 duration and increased seed-set efficiency. This work demonstrates that yield increases due to resistance to H. glycines can be attained by different physiological mechanisms associated with the different resistance sources and probably are controlled by different genes. This opens the possibility of pyramiding genes conferring resistance by different mechanisms. © Crop Science Society of America.Fil: Rotundo, José Luis. University of Iowa; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Tylka, G.L.. Syngenta Crop Protection; Estados UnidosFil: Pedersen, P.. University of Iowa; Estados Unido