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Title: Maize Leaf Epiphytic Bacteria Diversity Patterns Are Genetically Correlated with Resistance to Fungal Pathogen Infection

Author
item Balint-Kurti, Peter
item SIMMONS, SUSAN - UNC-WILMINGTON
item BLUM, JAMES - UNC-WILMINGTON
item BALLARE, CARLOS - IFEVA,UNIV BUENOS AIRES
item STAPLETON, ANN - UNC-WILMINGTON

Submitted to: Biology of Plant Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2009
Publication Date: 3/1/2010
Citation: Balint Kurti, P.J., Simmons, S., Blum, J., Ballare, C., Stapleton, A. 2010. Maize Leaf Epiphytic Bacteria Diversity Patterns Are Genetically Correlated with Resistance to Fungal Pathogen Infection. Biology of Plant Microbe Interactions. 23: 473-484

Interpretive Summary: The leaf surface, or phyllosphere, is a huge and under-studied ecological niche. Complex communities of micro-organisms exist on the leaf. Previous work has shown that on corn (maize) the make up of this community differs between lines. Most pathogens infecting the leaf exist for a time in the phylosphere and therefore it seems logical that different phylosphere communities might effect the progres of disease in different ways. Here we identify genes that control phylosphere diversity and show that in many cases they map to the same regions as genes that control reisstance to a leaf disease of maize. We speculate that the same genes are controlling both traits. The data support a model in which certain bacteria produce suppressive compounds that inhibit general microbial growth.

Technical Abstract: Plant leaves host a specific set of microbial epiphytes. These phyllosphere organisms form a large community, with annual crops alone covering millions of hectares each year. Host plant genetic factors and abiotic stresses such as UV-B are key in shaping patterns of epiphyte diversity; we analyzed the genetic architecture of Zea mays host control. • Bacterial rDNA diversity was measured with molecular methods in a maize recombinant inbred mapping population with and without ultraviolet-B radiation, and in a factorial experiment to test for genetic correlation between host-plant pathogen resistance and phyllosphere diversity. • Thirteen UV-B-specific loci and ten loci with an environment-independent genetic effect on bacterial diversity were found. Several of the UV-B-specific loci co-occurred with loci involved in fungal leaf blight resistance in the field. A factorial experimental design was used to test the effects of antibiotic treatment and blight-resistant genotype on bacterial diversity; the resistant genotype had less beta diversity under control no-antibiotic conditions. • The coincidence in chromosomal locations that control bacterial diversity with locations that control fungal pathogen resistance suggests two possible mechanistic models: first, that leaf attractiveness leads to diverse bacterial epiphytes and facilitates rapid fungal pathogen spread, or that, alternatively, pathogen susceptibility is due to loss of a suppressive bacterial species. The antibiotic treatment results support the second model.