ARS | Publication request: Assessment of Procedures to Quantify Insect Damage on Sweetpotato Roots

Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: February 15, 2007
Publication Date: June 15, 2007
Citation: Jackson, D.M. 2007. Assessment of Procedures to Quantify Insect Damage on Sweetpotato Roots. HortScience. 42(3):451-452.

Technical Abstract: There are many soil insect pests that damage sweetpotato roots in the southeastern United States. After the roots are harvested, it is difficult to distinguish between injury symptoms caused by different pest species. Also, pest populations and subsequent damage levels fluctuate significantly from year to year, from location to location, from field to field, and sometimes within fields. To further complicate the quantification of pest impact, we have found a positive relationship between damage ratings and root weight, and sweetpotato genotypes vary widely in yields within grades. Therefore, it is difficult to interpret comparisons of insect ratings between high yielding and low yielding genotypes. Thus, a sweetpotato genotype that produces many small roots might appear more resistant than a genotype that produces many large roots, even if the actual resistance levels were the same in these genotypes. Therefore, we developed a new algorithm that better estimates pest damage ratings for sweetpotato genotypes that vary widely in yields and pest resistance. Currently, we rate every root within a plot for insect damage. This is done after roots are weighed and separated into four quality grades: small canners, large canners, U.S. #1’s, and jumbos. This procedure is slow, labor intensive, and limits the number of genotypes we can evaluate each season for pest resistance. Therefore, we used computer simulations to evaluate different sub-sampling procedures for quantifying pest damage on known populations of several sweetpotato genotypes that were established by individually rating every root in 25-plant field plots replicated 4 times. Sub-sampling schemes for predetermined numbers of total roots included: 1) random selection, 2) fixed sample sizes within grades, and 3) proportional sample sizes within grades. It is hoped that through these efforts, a more-efficient sampling and evaluation procedure can be developed that will allow more “through-put” in the USDA-ARS host plant resistance breeding program for sweetpotato.