Reactions of winter wheat to Mycosphaerella graminicola ( anamorph Septoria tritici ) LUBOMÍR VÌCHET

Reaction of six winter wheat cultivars and lines (V l a s t a , Š á r k a , C h a r g e r , 00ST022, SG-U8044C a SG-U2113B) to Mycosphaerella graminicola isolate BR-331 and UH-05 on leaf segments of the detached second seedling leaf of cultivars placed on water agar with bezimidazole in clear plastic box were tested. The isolate BR 331 produced high occurrence of the disease in the cultivar Šárka, middle occurrence (the percentage covered by lesions bearing pycnidia) in the cultivar Vlasta and SG-U8044C and low occurrence in the line 00ST0022. The isolate UH-105 produced high occurrence in the cultivar 00ST022 and middle occurrence in the cultivar Vlasta. The cultivar Charger was resistant. The cultivar Šárka was attacked at least. Results show on different virulence of M. graminicola isolates to wheat cultivars.


INTRODUCTION
Septoria tritici leaf blotch, caused by the fungus Mycospaerella graminicola (Fukel) J. Schrõt.In Cohn (sexual stage Septoria tritici Roberge in Desmaz), is one of the most serious disease of wheat worldwide.However, progress in breeding wheat cultivars resistant to M. graminicola is constrained at present because very little is known about genetics of resistance.K e m a et al. (1996 a,b) showed that the host-pathogen interactions in septoria tritici blotch involve resistances specifically effective against particular isolates, as well as isolate non-specific resistance.Methods of detecting interactions between wheat and M. graminicola genotypes are therefore required.
Reaction of winter wheat to Mycosphaerella graminicola (anamorph Septoria tritici) was tested on detached seedling leaf segments.

MATERIAL AND METHODS
Six or eight winter wheat cultivars and breeding lines were used to finding out of reactions to three isolates of M. graminicola, UH105 (Uhøetice,) R116 (Ruzynì) and BR331 (Branišovice) from the Czech Republic.Inoculum was produced from sporulating cultures of the pathogen, grown on potato dextrose agar for 7 days under near-ultraviolet light.Cultures were flooded with sterile distilled water and scraped to release conidia.Concentration of 10 6 spores ml -1 was prepared.Wheat seedlings were evenly sprayed with spore suspension (20 ml) per pot by means of hand sprayer.The leaves were left to dry for 30 min.before 3 cm sections were cut from the middle of the primary leaves.Technique of detached seedling leaves placed on water agar according A r r a i a n o et al. ( 2001) were used.Water agar (10 g l -1 ) containing 80 mg l -1 benzimidazole was dispensed into non-sterile clear polystyrene boxes (10,5x19,5 cm with 12 small boxes 3x5 cm).Rectangular sections (2x5 cm) were cut from the centre of the agar.Leaf segments were lied upper section across the gap so that the cut ends rested on the agar.Strips of agar from the gap were placed over cut ends of the leaf segments so that they were not exposed, thereby delaying senescence.Boxes were closed and covered with aluminium foil.After incubation at 20°C for 48 h in the climate chamber the boxes were uncovered.The percentage leaf area covered by lesions bearing pycnidia was scored five times during period of 19-24 days after inoculation.Experiments were made in four replications.

RESULTS AND DISCUSSION
Several specific interactions, i.e. resistance or susceptibility of cultivars to the isolate UH105 were observed.The breeding line OOST022 (Tab. 1) was susceptible.The line SG-U8044C was middle resistant.The cultivars Charger and F1463 were resistant.The cultivars Šárka, Vlasta, SG-U2113B and SG-U 7157A were specific resistance resistant to this isolate.On the contrary the cultivar Šárka and the line SG-U8044C were medium susceptible to the isolate BR331.Specific resistance with low levels of pycnidial lesions covering the leaf had the cultivars Vlasta, Charger and lines OOST022 and SG-U2113B.The isolate R116 shoved low levels of pycnidial lesions in tested cultivars and breeding lines.The cultivar Šárka counted among the most susceptible cultivars in field experiments in 1997-2000 to M. graminicola (Š í p et al., 2001).The cultivar Vlasta was middle resistant.Means of single isolates to produce the disease in single cultivars indicate different virulence of used isolates.The isolate R116 bring about lower disease severity in all cultivars.Likewise cultivar mean show differences in resistance to M. graminicola.Most resistant was Charger and most susceptible was OOST022.Our results indicate different virulence of M. graminicola isolates to single cultivars and breeding lines of winter wheat.The detached leaf technique could be a useful component to field trials and an alternative to whole seedling assays in assessing cultivar resistance and investigating the genetics of the host-pathogen interaction (A r r a i a n o et al., 2001).

REFERENCES
A r r a i a n o L. S., B r a d i n g P. A., B r o w n J. K. M., 2001.A detached seedling leaf techni que to study resistance to Mycosphaerella graminicola (anamorph Septoria tritici) in wheat.Plant Pathology 50: 339 346.K e m a G. H., A n n o n e J. H., S a y o u n d R. S., Va n S i l f h o u t C. H., Va n G i n k e l M., de B r e e J., 1996a.Genetic variation for virulence and resistance in the wheat Myco sphaerella graminicola pathosystem.I. Interactions between pathogen isolates and host cultivars.Phytopathology 86: 200 12.K e m a G. H. J., S a y o u s R. S., A n n o n e J. H., Va n S i l f h o u t C. H., 1996b.Genetic variation for virulence and resistance in the wheat Mycosphaerella graminicola pa thosystem.II.Analysis of interactions between pathogen isolates and host cultivars.Phytopathology 86: 213 20.Š í p V., S t u c h l í k o v á E., C h r p o v á J., 2001.The response of selected winter wheat culti vars to artificial infection with Septoria tritici under field conditions.Czech J. Genet.Plant Breed.37: 73 81.

Table 1 .
Percentage area of leaves segments of wheat cultivars and breeding lines covered by lesions bearing pycnidia of Mycosphaerella graminicola isolates 2003