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Submitted to: Southern Soybean Conference Proceedings
Publication Type: Abstract Only Publication Acceptance Date: 3/7/2012 Publication Date: 3/7/2012 Citation: Stetina, S.R., Smith, J.R., Ray, J.D. 2012. Soybean lines evaluated for resistance to reniform nematode. Southern Soybean Conference Proceedings. March 7-8, 2012. Interpretive Summary: Technical Abstract: Seventy-four wild and domestic soybean (Glycine max and G. soja) lines were evaluated for resistance to reniform nematode (Rotylenchulus reniformis) in growth chamber tests with a day length of 16 hours and temperature held constant at 28 C. Several entries for which reactions to reniform nematode were previously reported were included to serve as controls. Due to space limitations, entries were divided into five sets, and each line was evaluated in two separate screenings. The experimental design for each screening was a completely randomized design with 5 replications. A single plant of each soybean line was established in a container filled with 120 cm3 of a steam-sterilized soil mixture. Upon stand establishment (approximately 5 days after planting), 500 reniform nematodes suspended in 1 ml water were added to the soil in each container. A second inoculation was conducted one week later resulting in a total inoculum level of 1,000 nematodes (mixed vermiform life stages) per container. Root infection was measured four weeks after the second inoculation. Plant roots were separated from soil, stained with red food coloring using standard protocols, and the number of swollen females attached to the roots counted. Root fresh weights were determined and counts were expressed as females per gram of root to adjust for differences in size of the root systems. Classification of entries was based on the percentage of infection as compared to the susceptible genotypes Morsoy RTS4706N (sets 1 and 3), Delta King DK4968 (sets 1, 2, and 3), Braxton (sets 4 and 5), and PI 88788 (sets 4 and 5): nematode index <10% = resistant, 10-30% = moderately resistant, 31-60% = moderately susceptible, and >60% = susceptible. Both relative infection and consistency of phenotype across tests contributed to identification of the best materials. One accession, PI 404166, was resistant to reniform nematode, consistent with previous reports. Twenty-two entries were moderately resistant. Of these, 8 entries were previously untested, so this study is the first to document moderate resistance to reniform nematode in the breeding lines DS 97-84-1, 02011-126-1-1-2-1, and 02011-126-1-1-5-1; released germplasm lines DS-880 and DS4-SCN05; and accessions PI 417077, PI 507354, and PI 567516 C. A total of 30 entries were moderately susceptible, with 16 entries previously untested including registered germplasm line SS93-6181, the breeding lines LG01-5087-5, 02016-1-5-1-4, 02016-1-5-1-1, 02016-2-3-1-3-1, 02016-1-5-1-2, JDR-6662, and JDR-6676; the cultivars Clark and 5601T, non-nodulating ‘Clark’ isoline PI 547419, and accessions PI 417321, PI 467312, PI 594692, PI 561287 B, and PI 597413. Twenty-one entries were susceptible with 11 entries previously untested. Cultivars 5002T, Stafford, Lee 74 (parent cultivar Lee previously reported as susceptible), and Jackson; accessions PI 416937, PI 417274, PI 423941, PI 587982 A, and PI 603751 A; registered germplasm line D68-0099 (derived from susceptible cultivar Lee), and wild Glycine soja accession PI 468916 were classified as susceptible. Results from this study were inconsistent with previous reports in that 9 entries rated as moderately susceptible and 4 entries rated as susceptible in this test were reported as resistant to reniform nematode by other researchers. Identification of resistance is the first step in developing resistant soybean cultivars that will benefit growers in the Mid South, where soybean acreage on reniform nematode-infested fields has increased in recent years. |
