Abstract
ABSTRACT Monosporascus root rot and vine decline (MRRVD) is an important disease in the melon crop in Brazil. In our research, we evaluated the reaction of 45 melon genotypes to M. cannonballus in two successive cropping seasons in a greenhouse. Melon seedlings were transplanted into naturally infested soil. The evaluation of the genotypes was performed after 55 days, using a score scale to group each genotype into one of five classes and to calculate the disease severity index. None of the genotypes showed an immune reaction to M. cannonballus, regardless of the season. In the first cycle, only 28.9% ('AF 464', 'Auraprince', 'DRG 2278', 'Estoril', 'Guaporé', 'Kousto', 'Mabel', 'Magisto', 'Massaï', 'Nectar', '8530', 'RZ 34130' and 'RZ 34292') had a similar reaction to the high resistance to the MRRVD. Most genotypes (66.7%) behaved as moderately resistant while 4.4% were susceptible and none were highly susceptible. Conversely, in the second cycle, no genotype showed a reaction similar to high resistance while 42.2% behaved as moderately resistant, 48.9% as susceptible, and 8.9% as highly susceptible. The severity levels ranged from 7.5 to 60% and 27.5 to 92.5% for the first and second cycles, respectively. The genotypes 'DRG 2278', 'Estoril', 'Guaporé', 'Kousto', 'Mabel', 'Massaï', 'RZ 34130' and 'RZ 34292' were identified as highly resistant and moderately resistant in the first and second cycles of cultivation, respectively. Therefore, these genotypes are promising sources of resistance to M. cannonballus and should be preferred in commercial fields infested with the pathogen.
Highlights
The north-eastern region is responsible for95.7% (570.8 t) of melon production (Cucumis meloL.) in Brazil, highlighting the supply of fruits to the domestic and export markets
The present study aimed to evaluate the reaction of 45 melon genotypes inoculated with M. cannonballus in two successive crop cycles, under greenhouse conditions
A randomised block experimental design was used, with four replications, wherein each replicate consisted of a four-plant pot. In both cropping seasons, when melon plants reached 55 days after transplanting, roots were carefully extracted, washed in running water, and evaluated for severity of Monosporascus root rot and vine decline (MRRVD), using the score scale adapted by Bruton et al (2000), where 0 = healthy with no lesion or discolouration, 1 = slight discolouration, 2 = moderate discolouration and/or with lesions, 3 = moderate discolouration and/or slight maceration, 4 = severe discolouration and/or macerated root
Summary
L.) in Brazil, highlighting the supply of fruits to the domestic and export markets. The states of Rio. The symptoms of MRRVD can be observed in adult melon plants at the time of harvest (MARTYN; MILLER, 1996; COHEN et al, 2012), wherein yellowing, wilting and dryness of basal leaves occur, followed by vine decline. Countless control strategies against this disease have been tested, either in isolation or in association with others, but, none of them showed efficiency They can be effective when sustainable measures are incorporated (MEDEIROS et al, 2008), such as the use of green fertilisation (SALES JÚNIOR et al, 2017), post-harvest residue destruction (RADEWALD; FERRIN; STANGHELLINI, 2004), chemical control (PIVONIA et al, 2010), application of essential oils (FERNANDES et al, 2015; AWAD, 2016), use of plant-growth-promoting bacteria (ANTONELLI et al, 2013), use of biocontrol agents (ALEANDRI et al, 2015) and grafting on hybrid rootstocks of Cucurbita (AL-MAWAALI et al, 2016; EDELSTEIN et al, 2017). The present study aimed to evaluate the reaction of 45 melon genotypes inoculated with M. cannonballus in two successive crop cycles, under greenhouse conditions
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