Recent Introduction and Recombination in Colletotrichum acutatum Populations Associated with Citrus Postbloom Fruit Drop Epidemics in Sao Paulo, Brazil

Author(s)

Ciampi-Guillardi, Maisa ^{[1, 2]} ; Baldauf, Cristina ^[3] ; Souza, Anete Pereira ^[2] ; Silva, Geraldo Jose ^[4] ; Amorim, Lilian ^[1]

Affiliation

^[1] Univ Sao Paulo, Dept Plant Pathol & Nematol, BR-13418900 Piracicaba, SP - Brazil

^[2] Univ Estadual Campinas, Genet Engn & Mol Biol Ctr, BR-13083875 Campinas, SP - Brazil

^[3] Fed Rural Univ Semiarid Reg, Dept Anim Sci, BR-59625900 Mossoro, RN - Brazil

^[4] Fundecitrus, Fund Citrus Protect, BR-14807040 Araraquara, SP - Brazil

• Document type: Journal article
• Source: PHYTOPATHOLOGY; v. 104, n. 7, p. 769-778, JUL 2014.
• Web of Science Citations: 5

Abstract

Citrus crops in Sao Paulo State, Brazil, have been severely affected by postbloom fruit drop disease (PFD), which is caused by Colletotrichum acutatum. This disease leads to the drop of up to 100% of young fruits. Previous studies have assumed that this pathogen exhibits a clonal reproductive mode, although no population genetic studies have been conducted so far. Thus, the genetic structure of six C. acutatum populations from sweet orange orchards showing PFD symptoms was determined using nine microsatellite markers, enabling inference on predominant mode of reproduction. C. acutatum populations exhibit a nearly panmictic genetic structure and a high degree of admixture, indicating either ongoing contemporary gene flow at a regional scale or a recent introduction from a common source, since this pathogen was introduced in Brazil only very recently. Sharing haplotypes among orchards separated by 400 km suggests the natural dispersal of fungal propagules, with the possible involvement of pollinators. A significant population expansion was detected, which was consistent with an increase in host density associated with crop expansion toward new areas across the state. Findings of moderate to high levels of haplotypic diversity and gametic equilibrium suggest that recombination might play an important role in these pathogen populations, possibly via parasexual reproduction or a cryptic sexual cycle. This study provides additional tools for epidemiological studies of C. acutatum to improve prevention and management strategies for this disease. (AU)

• FAPESP's process: 08/54176-4 - Molecular epidemiology and management of postbloom fruit drop of citrus in new planting areas in São Paulo State
• Grantee: Lilian Amorim
• Support Opportunities: Research Projects - Thematic Grants