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Plant Pathol J. 2016 Apr;32(2):123-35. doi: 10.5423/PPJ.OA.09.2015.0194. Epub 2016 Apr 1.

Principal Component Analysis and Molecular Characterization of Reniform Nematode Populations in Alabama.

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Department of Crop Science, College of Basic and Applied Sciences, University of Ghana, P.O. Box LG 44, Legon-Accra; Department of Natural Resources and Environmental Sciences, Alabama A & M University, Normal-AL, 35762.
Department of Natural Resources and Environmental Sciences, Alabama A & M University, Normal-AL, 35762.
Department of Entomology and Plant Pathology, Auburn University, Auburn, AL 36849.
Soil and Irrigation Research Centre, University of Ghana, P.O. Box LG 44, Legon-Accra.


U.S. cotton production is suffering from the yield loss caused by the reniform nematode (RN), Rotylenchulus reniformis. Management of this devastating pest is of utmost importance because, no upland cotton cultivar exhibits adequate resistance to RN. Nine populations of RN from distinct regions in Alabama and one population from Mississippi were studied and thirteen morphometric features were measured on 20 male and 20 female nematodes from each population. Highly correlated variables (positive) in female and male RN morphometric parameters were observed for body length (L) and distance of vulva from the lip region (V) (r = 0.7) and tail length (TL) and c' (r = 0.8), respectively. The first and second principal components for the female and male populations showed distinct clustering into three groups. These results show pattern of sub-groups within the RN populations in Alabama. A one-way ANOVA on female and male RN populations showed significant differences (p ≤ 0.05) among the variables. Multiple sequence alignment (MSA) of 18S rRNA sequences (421) showed lengths of 653 bp. Sites within the aligned sequences were conserved (53%), parsimony-informative (17%), singletons (28%), and indels (2%), respectively. Neighbor-Joining analysis showed intra and inter-nematodal variations within the populations as clone sequences from different nematodes irrespective of the sex of nematode isolate clustered together. Morphologically, the three groups (I, II and III) could not be distinctly associated with the molecular data from the 18S rRNA sequences. The three groups may be identified as being non-geographically contiguous.


principal component analysis; reniform nematode; variation

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