Host suitability of soybean cultivars and breeding lines to reniform nematode in tests conducted in 2001.

Reproduction of reniform nematode Rotylenchulus reniformis on 139 soybean lines was evaluated in a greenhouse in the summer of 2001. Cultivars and lines (119 total) were new in the Arkansas and Mississippi Soybean Testing Programs, and an additional 20 were submitted by C. Overstreet, Louisiana State Extension Nematologist. A second test of 32 breeding lines and 2 cultivars from the Clemson University soybean breeding program was performed at the same time under the same conditions. Controls were the resistant cultivars Forrest and Hartwig, susceptible Braxton, and fallow infested soil. Five treatment replications were planted in sandy loam soil infested with 1,744 eggs and vermiform reniform nematodes, grown for 10 weeks in 10 cm-diam.- pots. Total reniform nematodes extracted from soil and roots was determined, and a reproductive factor (final population (Pf)/ initial inoculum level (Pi)) was calculated for each genotype. Reproduction on each genotype was compared to the reproduction on the resistant cultivar Forrest (RF), and the log ratio [log(RF + 1) is reported. Cultivars with reproduction not significantly different from Forrest (log ratio) were not suitable hosts, whereas those with greater reproductive indices were considered suitable hosts. These data will be useful in the selection of soybean cultivars to use in rotation with cotton or other susceptible crops to help control the reniform nematode and to select useful breeding lines as parent material for future development of reniform nematode resistant cultivars and lines.

Host suitability in soybean cultivars for the reniform nematode, 2000 tests.

In greenhouse pot experiments during summer 2000, 118 soybean cultivars were tested to determine their suitability as hosts for the reniform nematode, Rotylenchulus reniformis. The cultivars included 115 new entries into the Arkansas and Mississippi soybean variety testing programs and three entries submitted by an extension nematologist from Texas. Also included in the tests were the R. reniformis-resistant cultivars Forrest and Hartwig, the susceptible cultivar Braxton, and fallow R. reniformis-infested soil that served as controls. Total number of eggs and nematodes extracted from both the soil and roots from each pot and reproductive indices (Pf/Pi) were calculated for each cultivar. The ratio of the Pf/Pi of each cultivar to the Pf/Pi of Forrest (RF), and the log ratio[log(10) (RF + 1)], are reported. Cultivars with reproductive indices that were greater than the reproductive index on Forrest were considered to be suitable hosts for R. reniformis. These data will be useful in the selection of soybean cultivars to use in rotation with cotton or other susceptible crops to help control the reniform nematode.

Host suitability in soybean cultivars for the reniform nematode, 1999 tests.

Two hundred twenty-six soybean cultivars were tested in greenhouse pot experiments during summer 1999 to determine their suitability as hosts for the reniform nematode, Rotylenchulus reniformis. The cultivars included new entries into the Arkansas and Mississippi soybean variety testing programs and entries submitted by extension nematologists from Auburn University and Louisiana State University. Also included in the R. reniformis tests were the resistant cultivars Forrest and Hartwig, the susceptible control Braxton, and fallow infested soil that served as controls. Total number of eggs + nematodes extracted from the soil and roots per pot, reproductive indices (Pf/Pi) based on the number of nematodes extracted from the soil and roots/initial inoculum level, calculated for each cultivar, and the ratio of the Pf/Pi of each cultivar to the Pf/Pi of Forrest are reported. Cultivars with reproduction not significantly different from Forrest were not suitable hosts, whereas those with greater reproductive indices were considered suitable hosts. One of the 12 cultivars of the relative maturity group (RMG) <=4.4 was not a suitable host. For the 4.5 to 4.9 RMG, 24 of 72 cultivars were not suitable hosts, whereas 9 of 41 cultivars in RMG 5.0 to 5.4 were not suitable hosts. In the 5.5 to 5.9 RMG cultivars, 11 of 66 were not suitable hosts; for the 6.0 or greater RMG, 11 of 35 were not suitable hosts. These data will be useful in the selection of soybean cultivars to use in rotation with cotton or other susceptible crops to help control the reniform nematode.

Reniform nematode resistance in selected soybean cultivars.

Two hundred eighty-two soybean cultivars from the variety testing programs of Arkansas and Mississippi were tested in greenhouse pot experiments during summer 1998 to identify soybean cultivars with resistance to the reniform nematode, Rotylenchulus reniformis. Also included in the tests were the resistant cultivars Forrest and Hartwig, the susceptible control Braxton, and fallow infested soil, which were used as controls. Numbers of reniform nematode extracted from the soil and roots and the ratio of the numbers reproducing on each cultivar compared to the number reproducing on Forrest are reported. Cultivars with reproduction not significantly different from Forrest were classified resistant, whereas those with greater reproductive indices were considered susceptible. One of the 18 cultivars of relative maturity group (RMG) /=6.0 were classed as resistant. These data will be useful in the selection of soybean cultivars to use in rotation with cotton to help control the reniform nematode.