Evaluation of the Core Collection Approach for Identifying Resistance to Meloidogyne arenaria in Peanut

Abstract

Core collections are representative subsamples of germplasm collections. Use of core collections may improve the efficiency of germplasm evaluations by reducing the number of accessions evaluated while increasing the probability of finding genes of interest. The peanut (Arachis hypogaea L.) core collection has been examined for resistance to the peanut root‐knot nematode [Meloidogyne arenaria (Neal) Chitwood race 1]. Resistant indicator accessions from screening the core collection identified 39 clusters in the entire germplasm collection that should be examined more thoroughly. The objective of this study was to evaluate how effective a two‐stage core screening approach would be in identifying resistance to M. arenaria in the entire U.S. germplasm collection of peanut. Accessions from 30 clusters having resistant indicator accessions and from four clusters having very susceptible indicator accessions were tested for resistance in two greenhouse trials. This second stage screening identified 259 accessions that had a mean egg‐mass rating of 2.5 or less. Twenty‐eight of these accessions had a mean egg‐mass rating of 1.0 or less. There were relatively large numbers of resistant accessions from China and Japan compared with the percentages of the germplasm collection that originated from these countries. The efficiency of identifying accessions resistant to M. arenaria was greater in clusters having resistant indicator accessions than in clusters having susceptible indicator accessions. These results demonstrate that the use of a two‐stage screening approach with a core collection can improve the efficiency of identifying valuable genes in germplasm collections.

Reaction of the Core Collection of Peanut Germplasm to Sclerotinia Blight and Pepper Spot1

“…The core collection is comprised of 831 entries selected at random (1%), at random by country of origin (26%), and by multivariate clustering of phenotypic descriptor information (73%) to minimize repetitiveness in the collection while representing the collection's genetic diversity (16,18). The peanut core collection has been previously evaluated for resistance to tomato spotted wilt virus (TSWV), Rhizoctonia limb rot, late leaf spot, peanut root knot nematode, preharvest aflatoxin contamination, early leaf spot, and Cylindrocladium black rot (2,13,16,17,19). To our knowledge, the core collection has not been previously evaluated for reaction to Sclerotinia blight.…”

Geographical Distribution of Genetic Diversity in Arachis hypogaea

“…We have previously reported that China appears to be valuable geographical sources of resistance to this nematode (Holbrook et al, 2000a). Second-stage screening of selected groups of accessions from the entire germplasm collection confirmed that observation (Holbrook et al, 2000b). Although peanut is not native to China, it has been cultivated widely there for several centuries (Hammons, 1982), and M. arenaria is an important pathogen of peanut in China (Minton and Baugard, 1990).…”

“…Second-stage screening of selected groups of germplasm from Japan indicated that this country is an important source for material with resistance to this pathogen (Holbrook et al, 2000b).…”

Status of the Arachis Germplasm Collection in the United States

“…Second-stage testing, considering only those sets developed using the multivariate approach (Sets 4 through 8), would have resulted in the identification of one resistant accession for every eight entries examined. Holbrook et al (2000b) evaluated the effectiveness of Table 3. Efficiency of germplasm screening approaches for resistance to late leaf spot in peanut.…”