Selection of watermelon genotypes for resistance to bacterial fruit blotch

Abstract

Bacterial fruit blotch, caused by Acidovorax citrulli, is a serious threat to the watermelon crop in Brazil. To date, there are no disease-resistant varieties, thus requiring research seeking sources of resistance. To select genotypes with potential use in the management of fruit blotch, the resistance level of watermelon genotypes belonging to the Cucurbits Germplasm Active Bank for the Brazilian Northeast (Banco Ativo de Germoplasma de Cucurbitáceas para o Nordeste Brasileiro-BAG) of Embrapa Semiárido was evaluated at different plant developmental stages: seeds (74 genotypes), seedlings and plants before flowering (29 genotypes) as well as plants during flowering and fruiting (seven genotypes). The genotypes were evaluated for the incidence or severity of the disease, which was estimated with the aid of descriptive scales. Additionally, A. citrulli transmission was determined in seeds derived from symptomatic and asymptomatic fruits. No watermelon genotype was immune to fruit blotch, and the majority showed variations in resistance responses. However, the genotypes BGCIA 979, BGCIA 34 and Sugar Baby showed high levels of resistance at most stages of plant development, thereby suggesting that these genotypes possess fruit blotch resistance genes that could be used in breeding programs. Seeds from symptomatic and asymptomatic fruits of the seven tested genotypes showed transmission rates of A. citrulli up to 35.3 % and 8.7 %, respectively. These results confirm that asymptomatic fruits can harbor contaminated seeds that are responsible for the transmission of the bacteria.

Polyphasic analysis of Acidovorax citrulli strains from northeastern Brazil

“…In Brazil, over the last decade, BFB has had a severe economic impact, particularly on melon (Carvalho et al, 2013). Given that 70 % of the studied strains originated from the same municipality/ state, i.e., Baraúna-RN, it is possible that A. citrulli were introduced into the region through the importation of infected seeds, as proposed by Assis et al (1999).…”

“…and Nakai) producing regions throughout the world (Burdman and Walcott, 2012). In Brazil, the most significant economic impact of BFB is on melon crops (Carvalho et al, 2013), mainly in the northeastern region, where yield losses are estimated at 40-50 %, but might reach 100 % (EPPO, 2010).…”

Characterization, Identification and Expression Profiling of Genome-Wide R-Genes in Melon and Their Putative Roles in Bacterial Fruit Blotch Resistance

“…The lesions then become necrotic, causing decay and cracks in the fruit. These lesions expose the plant to secondary infections and cause A. citrulli to colonizes the pulp, eventually allowing the seed to become contaminated [17]. BFB causes 80-100% losses in production under favorable environmental situations, especially during the rainy season and in regions with highly fluctuating temperatures [18,19].…”

Characterization, Identification and Expression Profiling of Genome-Wide R-Genes in Melon and Their Putative Roles in Bacterial Fruit Blotch Resistance

“…The lesions then become necrotic, causing decay and cracks in the fruit. These lesions expose the plant to secondary infections and cause A. citrulli to colonize the pulp, eventually allowing the seed to become contaminated [17]. BFB causes 80-100% losses in production under favorable environmental situations, especially during the rainy season and in regions with highly uctuating temperatures [18,19].…”