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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Publications at this Location » Publication #335542

Title: Cucurbits powdery mildew race identity and reaction of melon genotypes

item RABELO, HUDSON - Sao Paulo State University (UNESP)
item SANTOS, LUCAS - Sao Paulo State University (UNESP)
item DINIZ, GUILHERME - Sao Paulo State University (UNESP)
item MARIN, MARCUS - Sao Paulo State University (UNESP)
item BRAZ, LEILA - Sao Paulo State University (UNESP)
item McCreight, James - Jim

Submitted to: Pesquisa Agropecuária Tropical
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2017
Publication Date: 1/12/2018
Citation: Rabelo, H.O., Santos, L.S., Diniz, G.M., Marin, M.V., Braz, L.T., Mccreight, J.D. 2018. Cucurbits powdery mildew race identity and reaction of melon genotypes. Pesquisa Agropecuária Tropical. 47:440–447.

Interpretive Summary: Cucurbit powdery mildew is constant threat to melon (cantaloupe, muskmelon, honeydew) wherever it is grown. The disease is incited by three airborne fungal parasites, most notably Podosphaera xanthii. Host plant resistance to the disease is environmentally friendly, i.e., no pesticide is required, but new races have been observed when new resistance genes are deployed. Research on powdery mildew in South America has been limited to date. This report documents occurrence P. xanthii race 4 for the first time in the State of Sao Paulo, Brazil. Twelve melon accessions from various parts of Brazil expressed resistance to race 4, and would, as they are locally adapted, be ideal parents for development of race 4-resistant breeding lines and F1 hybrids, pending morphological characterization and inheritance studies of the reactions.

Technical Abstract: Genetic resistance is one of the most suitable strategies to control cucurbit powdery mildew (CPM) on melon, incited by Podosphaera xanthii or Golovinomyces orontii. However, many races of these pathogens have been reported worldwide in recent years, what may compromise the effectiveness of this method. Thus, annual surveys of CPM races and the screening of germplasm for new sources of genetic resistance provide a vital support to melon breeding programs. This study aimed at identifying a natural population of CPM race under greenhouse conditions, as well as evaluating the reaction of local and exotic melon germplasm for CPM-resistance. CPM race identity was based on the reaction of eight race differentials: Védrantais, Nantais Oblong, PMR 45, PMR 5, WMR 29, Edisto 47, PI 414723 and PI 124111. Fifty-nine melon genotypes were evaluated, 53 of them being germplasm accessions, and six net melon elite-inbred lines, besides two net melon-type cultivars (Louis and Fantasy). Plants were evaluated using a visual scale for leaf lesions. The causal pathogen was confirmed to be P. xanthii, based on the presence of fibrosin bodies in conidia and the complete resistance response of winter melon (Benincasa hispida). Race 4 was identified for the first time in the São Paulo state, Brazil. Genotypes A19, A30, A32, C67, C384, JAB-3, JAB-7, JAB-9, JAB-11, JAB-18, JAB-20 and Solarking showed to be resistant to the race 4.