Magnaporthe oryzae Populations Adapted to Finger Millet and Rice Exhibit Distinctive Patterns of Genetic Diversity, Sexuality and Host Interaction

Abstract

In this study, host-specific forms of the blast pathogen Magnaporthe oryzae in sub-Saharan Africa (SSA) were characterised from distinct cropping locations using a combination of molecular and biological assays. Finger millet blast populations in East Africa revealed a continuous genetic variation pattern and lack of clonal lineages, with a wide range of haplotypes. M. oryzae populations lacked the grasshopper (grh) element (96%) and appeared distinct to those in Asia. An overall near equal distribution (47-53%) of the mating types MAT1-1 and MAT1-2, high fertility status (84-89%) and the dominance of hermaphrodites (64%) suggest a strong sexual reproductive potential. Differences in pathogen aggressiveness and lack of cultivar incompatibility suggest the importance of quantitative resistance. Rice blast populations in West Africa showed a typical lineage-based structure. Among the nine lineages identified, three comprised ~90% of the isolates. Skewed distribution of the mating types MAT1-1 (29%) and MAT1-2 (71%) was accompanied by low fertility. Clear differences in cultivar compatibility within and between lineages suggest R gene-mediated interactions. Distinctive patterns of genetic diversity, sexual reproductive potential and pathogenicity suggest adaptive divergence of host-specific forms of M. oryzae populations linked to crop domestication and agricultural intensification.

Characterization and Phylogenetic Analysis of Magnaporthe spp. strains on VariousHosts in Iran

“…AFLP marker was also recognized here to be the most useful DNA fingerprinting tool for resolving the high genetic variation of this fungus compared with other fingerprinting techniques applied by several previous researchers such as RAPD and rep-PCR (6,15,(22)(23)(24). However, this research confirmed results obtained by JavanNikkhah (15) showing the low genetic variation among strains isolated from rice in Iran.…”

Magnaporthe oryzae Genetic Diversity and Its Outcomes on the Search for Durable Resistance

“…Similar results were obtained in Korea, when the analysis of 254 isolates demonstrated that all of them also belonged to MAT1-1 (Park, et al, 2008). In Africa studies revealed that 29% of isolates belongs to MAT1-1 and 71% to MAT2-2, but none of the isolates was hermaphrodite, avoiding crossing among them (Takan et al 2011). When two M. orizae populations from Himalayas were analyzed, it was found that 22% of the isolates belonged to MAT1-1 and 43% to MAT1-2, and isolates male fertile and hermaphrodite were detected, suggesting a possible occurrence of sexual recombination in this region (Kumar et al, 1999).…”

“…On the Philippines, 1156 isolates were obtained on 38 cultivars sowed in two growing seasons and after analysis were grouped in only ten lineages (Chen et al, 1995). Simple population structure was also observed in Europe (Roumen et al, 1997) and Africa, when isolates from four different countries were separated in nine lineages (Takan et al, 2011). Results found in the literature reports a limited number of the pathogen lineages, showing a clonally typical population structure (Levy et al, 1993;Xia et al, 1993;Xia et al, 2000).…”

Identification of Blast Resistance in a Core Collection of Foxtail Millet Germplasm

“…Node, neck, and stem tissues are also infected in addition to leaf sheaths. The blast pathogen infects several cereal crops, including rice, wheat, pearl millet, finger millet, and foxtail millet, and several grasses (12,13,21,26). The pathogen is variable but highly specialized in its host range.…”