Growth Chamber Assay for Evaluating Resistance to Athelia rolfsii

Abstract

ABSTRACT Planting resistant cultivars is most sustainable method for managing Athelia rolfsii (= Sclerotium rolfsii), one of the most damaging pathogens of peanut worldwide. However, evaluating germplasm for resistance in the field can be complicated by unfavorable environmental conditions, uneven distribution of sclerotia in soil, and difficulty in growing non-standard peanut genotypes such as wild species. Thus, a growth-chamber assay was used to screen for resistance to A. rolfsii in the laboratory. Thirteen peanut genotypes were used to test the assay: cultivars Georgia-03L, Georgia-12Y, Florida-07, Georgia-07W, Tamrun OL02, FloRun ‘107′, Georgia-06G, and U.S. mini-core accessions CC038 (PI 493581), CC041 (PI 493631), CC068 (PI 493880), CC384 (PI 155107), CC650 (PI 478819), and CC787 (PI 429420). Lesion length, as well as length of visible mycelium, on the main stem and a side stem were recorded at 4, 7, 10, and 13 days after inoculation. In general, patterns of lesion and mycelium growth were similar. The most resistant genotypes, Georgia-03L and CC650, had the smallest lesions and least mycelium growth. However, Georgia-12Y, one of the most resistant cultivars available today, appeared less resistant than Georgia-03L in the assay. Other commercial cultivars were intermediate in lesion and mycelium lengths. The most susceptible entries were CC038, CC041, and CC787. Despite limitations in discriminating among genotypes with intermediate resistance to A. rolfsii, these assays may be useful for pre-screening germplasm to identify physiologically resistant and highly susceptible entries, as well as for screening Arachis species that are difficult to grow in the field.