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Genetic Structure of Magnaporthe grisea Populations Associated with St. Augustinegrass and Tall Fescue in Georgia

May 2005 , Volume 95 , Number  5
Pages  463 - 471

L. P. Tredway , K. L. Stevenson , and L. L. Burpee

First and second authors: Department of Plant Pathology, University of Georgia, Athens 30602; and third author: Department of Plant Pathology, Georgia Station, University of Georgia, Griffin 30223

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Accepted for publication 23 December 2004.

Amplified fragment length polymorphisms (AFLPs) were used to estimate phylogenetic relationships within Magnaporthe grisea and determine the genetic structure of M. grisea populations associated with tall fescue and St. Augustinegrass in Georgia. Sixteen clonal lineages were identified in a sample population of 948 isolates. Five lineages were isolated from tall fescue (E, G1, G2, G4, and H), with lineage G4 comprising 90% of the population. Isolates from tall fescue were closely related to those from perennial ryegrass, weeping lovegrass, and wheat. Two M. grisea lineages were isolated from St. Augustinegrass (C and K), with lineage C comprising 99.8% of the population. Populations from crabgrass were dominated (98%) by lineage K, but also contained a single lineage C isolate. Haplotype diversity indices ranged from 0.00 to 0.29 in tall fescue populations and from 0.00 to 0.04 in St. Augustinegrass populations. Selection due to host species was the primary factor determining population structure according to analysis of molecular variance; host cultivar and geographical region had no significant effect. The host range of M. grisea lineages from turfgrasses was determined in growth chamber experiments and supports the prominent role of host species in determining the genetic structure of M. grisea populations from turfgrasses in Georgia.

Additional keywords: gray leaf spot , Pyricularia grisea .

© 2005 The American Phytopathological Society