1. Races distribution of Pyrenophora tritici-repentis in Algeria and consequences of new virulence type identification in some basis of P. tritici-repentis / Wheat pathosystem
BENSLIMANE1 H., L. LAMARI2, A. BENBELKACEM3, R. SAYOUD4 and Z. BOUZNAD5
1Université M’hamed Bougra, Boumerdès, Faculté des Science, Département de Biologie, Laboratoire de Biologie Moléculaire, 16 Rue de l’indépendance, Boumerdès, Algéria.
2 University of Manitoba, Department of Plant Sciences, Winnipeg, Manitoba, Canada, RT3 2N2.
3 Institut National de la Recherche Agronomique d’Algérie, Unité de Recherche de Constantine, Station ITGC, Elkhroub, Algéria.
4SYNGENTA, 5 chemin des citernes Skikda, Algérie. 5 Ecole Nationale Supérieure d’Agronomie, Département de Botanique, , El-Harrach, Alger, Algéria
Abstract
Tan spot, caused by Pyrenophora tritici-repentis, is a foliar disease of wheat, responsible for high economic losses in several wheat growing areas in the world. There are eight known races of P. tritici-repentis based on ability to induce necrosis and/or chlorosis on a set of differential cultivars. 55 isolates originating from diverse wheat growing regions in Algeria were studied to determine which races are present and to identify new races. Races 1, 4, 5, 6, 7 and 8 were found and a new virulence pattern was identified. Isolates with this pattern induced necrosis in durum wheat but failed to induce any disease in the common wheat genotypes in the differential set.
Material and Method
Fungal isolates:
55 isolates of P. tritici-repentis were used in this study., obtained from several infected wheat fields (Durum and bread wheat) in different cereal growing areas in Algeria. 3 isolates (Asc1, , Alg-3-24) corresponding, respectively, to 3 known races (1, 2, and 5) were used as controls (Benslimane and al., 2011).
Plant material: The differential set was made up of Durum and bread wheat
Inoculum production and Inoculation: Protocols of Lamari and Bernier (1989)
Bread wheat
A) Glenlea
B) 6B-662
C) 6B-365
D) Salamouni
Durum wheat
E) 4B-1149
F) Coulter
G) 4B-160
Results and Discussion
Isolates evaluated were grouped into six races
New virulence Type (Race 9 ??)
Race 4
Race 5
Race 6
Race 7
Race 8
Race 1
5 isolates from durum wheat showed a new virulence pattern, they were able to attach only durum wheat genotypes. Bread wheat genotypes harbored in their genomes the three gens (Tsn1, Tsc2, Tsc1) responsible for sensitivity to the three knows toxins (PtrToxA, PtrToxB and PtrToxC). This suggests that isolates with the new virulence pattern are not able to produce the three HTS.s. However, these isolates could possess a novel toxin(s)( Benslimane et al., 2011)
Distribution of Pyrenophora tritici-repentis races in Algeria
Percentage of each race founded in Algeria
The majority of isolates recovered
from the samples represented races 1 and 7, while races 4, 5, 6, and 8 were more rare.
Four races (1, 4, 7, and 8) were described in Algeria for the first time.
Consequences in Pyrenophora tritici-repentis/ Wheat Pathosystem
Conclusion
The presence of this putative new race, involves a significant impact on some bases of wheat / P. tritici-repentis pathosystem. It is recognized that races 2, 3 and 5 are considered as a basic races because they are able to produce a single toxin. While others races 1, 6, 7 and 8 are considered as combined from basic races (Strelkov and Lamari, 2003). The discovery of a new race able to produce a single toxin completely different from those known, imply the existence of a new basic race. Consequence , the model proposed by Strelkov and Lamari (2003) establishing the relationship between different races is permissible only when the host / pathogen interaction is considered for bread wheat. The introduction of durum wheat in the host differential set makes the hypothesis invalid (Benslimane, 2012).
This study reveals that the tan spot fungus is highly variable in Algeria and a new race has been identified. This new race should produce a new toxin(s) and should be a new basic race. These results showed that the genotypes used in the Algerian fields are more sensitive to race 7 and race 1. These investigations should be of direct benefit to wheat breeding programs aimed at incorporating resistance to this pathogen. Plant breeders require knowledge of what races are present in the pathogen population in order to determine which gene (s) should be present in resistant cultivars. The development of wheat varieties that resist to this disease under current and future climates in Algeria is therefore, of great importance.
Literature sited
Lamari L. and C.C. Bernier, Evaluation of wheat lines and cultivars to tan spot [Pyrenophora tritici-repentis] based on lesion type. Canadian Journal of Plant Pathology 11, 49–56.
Benslimane H Etude de la tache bronzée du blé en Algérie: Identification des races de l’agent causal Pyrenophora tritici-repentis (Died.) Drechs et diversité génétique. PhD. Thesis, ENSA, Algiers,157p.
Benslimane H., L. Lamari, A. Benbelkacem, R. Sayoud and Z. Bouznad, Distribution of races of Pyrenophora tritici-repentis in Algeria and identification of a new virulence type. Phytopathologia Mediterranea, 50: 203−211.
Strelkov S.E. and Lamari L Host- parasite interactions in tan spot [Pyrenophora tritici- repentis] of wheat. Canadian Journal of Plant Pathology 25: