Submitted to: Journal of Nematology
Publication Type: Abstract Only
Publication Acceptance Date: July 11, 2005
Publication Date: September 1, 2005
Citation: Stetina, S.R., Young, L.D. 2005. Comparison of female- and egg-based screening methods for reniform nematode resistance in cotton. Journal of Nematology. 37:397 Technical Abstract: Development of cotton germplasm with reniform nematode resistance requires evaluation of large numbers of plants. Shortening the time involved in the screening process is one way to increase the number of progeny that can be examined each year. In this study, the hypothesis that enumerating swollen females per gram of root is as efficient in identifying resistant genotypes as measuring eggs per gram of root was tested. The experiment was conducted four times between March 22 and December 20, 2004. Six cotton genotypes were used; three (Deltapine 33B, Deltapine 16, Stoneville 4892 BR) were susceptible and three (LA RN 4-4, LA RN 910, LA RN 1032) were resistant to reniform nematode. Twelve replicates of each genotype were planted in the greenhouse in 7.6-cm-diam. clay pots filled with soil mix (2 sand:1 infested field soil; Pi ranged from 4,425 to 23,615 reniform nematodes per 200 cm3 soil mix). Six replicates of each genotype were harvested 25 days after planting, the roots stained with red food coloring, and the number of females counted. The remaining plants were harvested 35 days after planting, eggs extracted from roots by stirring in a 0.615% NaOCl solution, and the number of eggs counted. Root fresh weights were recorded for all plants. Time required for growing plants, preparing samples, and counting was recorded. Contrasts were used to determine if the difference between a genotype and ‘Deltapine 33B’ based on females per gram of root was equivalent to the difference based on eggs per gram of root. Assessments based on females were equivalent to assessments based on eggs in all four runs of the experiment (P less than or equal to 0.05), which indicates that either life stage can be used. The time required for sample processing and counting was similar for both assessment methods, but an additional 10 days per cycle in the greenhouse were required for egg-based assessment. On a yearly basis, 40% more plants can be screened using a female-based assessment instead of an egg-based assessment.