Abstract
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.
Highlights
Melon (Cucumis melo) is grown and consumed worldwide, and its production increased from 1991 through 2013 (FAO 2016)
The experiment was carried out in a greenhouse naturally infected with powdery mildew, at the Department of Vegetable Crops and Aromatic-Medicinal Plants of the UNESP-FCAV, in Jaboticabal, São Paulo state, Brazil (21o15’22’’S, 48o18’58’’W and 595 m of altitude)
The summary reaction pattern of the differentials in this test was identical to that for P. xanthii race 4 (Table 1). This is the first report of race 4 in the São Paulo state, Brazil
Summary
Melon (Cucumis melo) is grown and consumed worldwide, and its production increased from 1991 through 2013 (FAO 2016). The total world production in 2013 was estimated at 29,499,542 t, of which 48.60 % was produced by China. Brazil is the 11th largest producer of melon in the world, being the first one in South America. In 2013, Brazil produced 565,900 t of melon, from which 33.82 % were exported (Seagri 2016). New production techniques contributed to increased melon production fields and higher yield, for example, by extending the growing seasons in some areas. Intensified cultivation systems have contributed to the higher occurrence of pests and diseases that may require the use of more pesticides. Among the diseases that affect cucurbits, powdery mildew (CPM) causes a significant damage in melon and occurs worldwide (McGrath 2017)
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