Genetic Similarity among Isolates of Pyrenophora tritici‐repentis, Causal Agent of Tan Spot of Wheat

Abstract

Tan spot, a foliar disease of wheat, is caused by the fungus Pyrenophora tritici-repentis. On susceptible wheat cultivars, P. tritici-repentis induces two distinct symptoms: tan necrosis and extensive chlorosis. Presently isolates of P. tritici-repentis are classified into 11 races based on their virulence on a set of wheat differential genotypes. In nature, this pathogen reproduces both sexually and asexually, but the extent of genetic variability in the P. tritici-repentis population of western Canada is unknown. This study was conducted to assess the genetic variability among different isolates of P. tritici-repentis and to determine if similarities among isolates are correlated with race classification or geographic origin of the isolates. Thirty-three isolates of P. tritici-repentis and one isolate each of P. teres f. sp. teres, P. teres f. sp. maculata, P. graminea, Helminthosporium sativum and an uncharacterized isolate were studied with 30 random amplified polymorphic DNA (RAPD) primers. Cluster analysis showed that all isolates had unique banding patterns and that clustering of isolates was independent of their race designation or geographic origin. Analysis of molecular variation (amova) showed that 96.8% of variability occurred among isolates and among race variability accounted for only 3.2% of the total variability. www.blackwell-synergy.com

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

“…On the other hand, P. tritici-repentis is a homothallic fungus that readily produces the sexual stage on field stubble, giving this fungal population the opportunity for adaptation by sexual recombination. 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).…”

“…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).…”

“…However, at present exists different studies where the aim consists in the characterization of genetic variability of Pyrenophora tritici-repentis population in different localities, areas and countries. (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).…”

“…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). Hence, we can assume that the occurrence the sexual state and long distance dispersal of inoculum could have contributed to pathogenic and genetic variability independent of geographic origin.…”

“…Within them Amplified Fragment Length Polymorphism (AFLP) (Friesen et al, 2005;Leisová et al, 2008), Enterobacterial Repetitive Intergenic Consensus (ERIC) and Repetitive Extragenic Palindromic (REP)-PCR technique (Mehta et al, 2004), Internal Transcribed Spacer Regions (ITS) (Lepoint et al, 2010), Mating Type locus (MAT) (Lepoint et al, 2010), Inter Simple Sequence Repeat (ISSR) (Moreno et al, 2009) and Random Amplified Polymorphisms DNA (RAPD) (Pujol Vieira dos Santos et al, 2002;Singh & Hughes, 2006), Restriction Fragment Length Polymorphism (RFLP), Toxin production genes (Tox A, Tox B and tox b genes) (Ali et al, 2010;Andrie et al, 2007;Lepoint et al, 2010).…”