Cryptic species and population genetic structure of Plasmopara viticola in Sao Paulo State, Brazil

Author(s)

Camargo, M. P. ^[1] ; Hong, C. F. ^[2] ; Amorim, L. ^[1] ; Scherm, H. ^[2]

Affiliation

^[1] Univ Sao Paulo, Escola Super Luiz de Queiroz, Dept Plant Pathol, BR-13418900 Piracicaba, SP - Brazil

^[2] Univ Georgia, Dept Plant Pathol, Athens, GA 30602 - USA

• Document type: Journal article
• Source: PLANT PATHOLOGY; v. 68, n. 4, p. 719-726, MAY 2019.
• Web of Science Citations: 1

Abstract

Downy mildew (Plasmopara viticola) is one of the most important diseases in grape-growing areas worldwide, including Brazil. To examine pathogen population biology and structure, P. viticola was sampled during the 2015/16 growing season from 516 lesions on nine grape cultivars in 11 locations in subtropical areas of Sao Paulo State, Brazil. For identification of cryptic species, a subsample of 130 isolates was subjected to cleaved amplified polymorphic sequence (CAPS) analysis, and for 91 of these isolates the ITS1 region was sequenced. These analyses suggest that the population of P. viticola in Sao Paulo State consists of a single cryptic species, P. viticola clade aestivalis. Seven microsatellite markers were used to determine the genetic structure of all 516 P. viticola isolates, identifying 23 alleles and 55 multilocus genotypes (MLGs). Among these MLGs, 34.5% were clonal and represented 93% of the isolates sampled. Four dominant genotypes were present in at least five different locations, corresponding to 65.7% of the isolates sampled. Genotypic diversity (11c; = 0.21-0.89) and clonal fraction (0.58-0.96) varied among locations (populations). Most populations showed significant deviation from Hardy-Weinberg expectations; in addition, excess of heterozygosity was verified for many loci. However, principal coordinate analysis revealed no clusters among locations and no significant isolation by distance was found, suggesting high levels of migration. The results indicate that downy mildew epidemics result from multiple clonal infections caused by a few genotypes of P. viticola, and reproduction of P. viticola in Sao Paulo State is predominantly asexual. (AU)

• FAPESP's process: 14/05522-8 - Spatio-temporal progress of grapevine rust and downy mildew in plants with different architectures
• Grantee: Meyriele Pires de Camargo
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 15/26106-5 - Grapevine downy mildew: temporal and spatial disease progress, population diversity and role of sexual reproduction in epidemic dynamics in subtropical regions
• Grantee: Meyriele Pires de Camargo
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate