Genetic Diversity of the Mating Type and Toxin Production Genes in Pyrenophora tritici-repentis

Abstract

Pyrenophora tritici-repentis, the causal agent of tan spot on wheat, is a homothallic loculoascomycete with a complex race structure. The objectives of this study were to confirm the homothallic nature of the pathogen, characterize mating type diversity and toxin production genes in a global collection of strains, and analyze how these traits are associated between each other and with existing races. The pseudothecia production capacity, race identification, mating type locus (MAT), internal transcribed spacer, and glyceraldehyde-3-phosphate dehydrogenase regions were analyzed in a selection of 88 strains originating from Europe, North and South America, North Africa, and Central and South Asia. Some (60%) strains produced pseudothecia containing ascospores, independent of their origin. Race identification obtained using the multiplex polymerase chain reaction targeting host-selective toxin (HST) genes was consistent, overall, with the results based on the inoculation of a set of differential wheat cultivars and confirmed the predominance of race 1/2 strains ( approximately 83%). However, discrepancies in race identification, differences from the reference tester strains, and atypical ToxA profiles suggest the presence of new races and HSTs. The MAT1-1 and MAT1-2 coding regions are consecutively arranged in a single individual, suggesting putative heterothallic origin of P. tritici-repentis. Upstream from the MAT is an open reading frame of unknown function (ORF1) containing a MAT-specific degenerate carboxy-terminus. The phylogenetic analysis of the MAT locus reveals two distinct groups, unlinked to geographical origin or ToxA profile. Group I, the best-represented group, is associated with typical tan spot lesions caused by races 1, 2, 3, and 5 on wheat. It is more homogenous than group II encompassing race 4 strains, as well as isolates associated primarily with small spot lesions on wheat leaves or other hosts. Group II could contain several distinct taxa.

Evaluation of CIMMYT germplasm for resistance to leaf spotting diseases of wheat

“…This ongoing study of virulence of P. tritici-repentis isolates in Mexico indicates race 1 is the most predominant race of the tan spot fungus. Race 2 isolates not yet observed in our study have been previously observed in Mexico (Lepoint et al 2010). The findings of this study confirm to previous race analysis studies (Lamari & Bernier 1989c) which observed race 1 isolates to be the most predominant race.…”

Pyrenophora tritici-repentis, Causal Agent of Tan Spot: A Review of Intraspecific Genetic Diversity

“…Several studies included tools for detection variability www.intechopen.com using of morphocultural, pathogenic, bioquemical and molecular variability. Several studies to detect variability include different tools, the most of them used pathogenic and genetic characterization (PCR techniques) (Ali et al, 2010;Andrie et al, 2007;Friesen et al, 2005;Leisová et al, 2008;Lepoint et al, 2010;Litcher et al, 2002;Mehta et al, 2004;Moreno et al, 2009;Pujol Vieira dos Santos et al 2002;Singh & Hughes 2006). A lesser extent of research focuses on characterization based on morphological and biochemical aspects (Diaz de Ackermann 1987; Gilchrist et al, 1984;Hosford, 1971;Hunger & Brown 1987, Moreno et al, 2008aPujol Vieira dos Santos et al, 2002).…”

“…There are numerous works that refer to the population structure of P. tritici-repentis in races Andrie et al, 2007;Lepoint et al, 2010;Manning et al, 2002;Strelkov et al, 2002;Lamari et al, 2003;2005 ). Some of these papers involve aspects as morpholocultural and virulence variability (Ali et al, 2010).…”

“…Some of these papers involve aspects as morpholocultural and virulence variability (Ali et al, 2010). In general in the mostly combined with molecular markers and PCR Ali et al, 2010;Andrie et al, 2007;Lepoint et al, 2010;Manning et al, 2002;Strelkov et al, 2002;Lamari et al, 2003;2005 , 2002). The pathogenic and molecular analyses (ISSR) showed intraspecific variability within P. tritici-repentis isolates and it was not possible to establish a relationship between this variability and the geographical regions and/ or wheat cultivars from where P. tritici-repentis isolates were obtained (Moreno et al, 2008a).…”

“…The occurrence of sexual recombination in nature is likely the reason for the high level of genetic variability among isolates of P. tritici-repentis (Singh & Hughes, 2006). Some works have studied the homothallic nature of P. triticirepentis using the specific molecular markers for detection of the MAT genes (Lepoint et al, 2010).Under favourable conditions conidiospores can travel 10-200 km (de Wolf et al, 1998). The tan spot fungus is also seed-borne and thus, long distance travel of fungal inoculum can occur by seed transmission (Singh & Hughes, 2006).…”