FUNGAL DISEASES OF IMPORTANT CULTIVATED GRASS SPECIES AND THEIR IMPORTANCE IN SEED PRODUCTION

Átírás

1 PANNON UNIVERSITY GEORGIKON FACULTY OF AGRICULTURAL SCIENCES Ph.D. SCHOOL OF CROP PRODUCTION AND HORTICULTURAL SCIENCES SUMMARY OF Ph.D. THESIS FUNGAL DISEASES OF IMPORTANT CULTIVATED GRASS SPECIES AND THEIR IMPORTANCE IN SEED PRODUCTION By ZSOLT VARGA Certified engineer of agriculture LEADING PROFESSOR: Dr. habil. GÉZA FISCHL Candidate of Agricultural Sciences, University Professor ASSOCIATE PROFESSOR: Dr. KÁROLY IVÁNY Candidate of Agricultural Sciences, Ret. reader Keszthely 2007

2 1. Preliminaries and aims of the research work Based on the ecology and geographical position of Hungary the quality of grass seeds produced in Hungary is worldwide appreciated. Its importance is even increased by the joining of the country to the European Union. The seed importation for itself may be a reason for an increased attention to the questions arising in plant protection. At the same time the plant health situation of natural grasses in Hungary is neglected in the science of plant protection. May I quote VAJNA and OROS (2005): We cannot find any references to the fungal diseases of the grasses even in the otherwise well-detailed Növényvédelmi Enciklopédia (1968) (Encyclopedy of Plant Protection), or in the newest textbooks (like for example Növényvédelem (1997) (Plant protection) and Kertészeti Növénykórtan (1993) (Plant Protection in the Horticulture) respectively. This statement is still valid, and surveying this theme one can state that we do not have proper information on the seed pathology of different grass species and cultivars, either. The Laboratory for Seed Pathology of the Hungarian Variety Testing Institute investigates certified seeds of a number of plant species, however grass seeds are not included in these tests (GERGELY 2005). It is characteristic for the Hungarian grass seed production that except for weed killing no chemicals are used in the plant production to be able to keep the costs lower. Grass seed disinfection is not a usual practice, no methods of disinfection and seed treatment have been developed. Based on a preliminary survey of these aspects we can state that our knowledge on fungal diseases occurring in the grass seed production is still poor. The health condition of seeds of cultivated grasses, the occurrence and frequency of seed-borne fungal pathogens and their effect on seed germination still constitute an unknown part - a white spot -, of our knowledge of plant pathology. Our research work made in frame of my Ph.D. work has revealed also newer questions which we included in the programme and made experiments and tests to give answers in the following topics: We conducted seed pathology investigations to ascertain species composition of fungal pathogens carried by the grass seeds, to ascertain what the dominance relations of these fungi are what possible effects they have on the germination of seeds and on the development of the seedlings. 2

3 We investigated whether there is a correlation between the species composition of pathogenic fungi found on seed surface and those damaging the grasses during production. We investigated whether far ultraviolet irradiation as an alternative seed treatment has an effect on seed germination and fungal infection of seeds. We investigated which pathogenic fungi damage the cultivated grasses. During the season which is the period when the fungal pathogens attack the grasses, and to what extent do they damage the plants? What resistance or sensitivity may different grass species have to the fungal pathogens? In field experiments using fungicides we investigated what possible effects they have on the biomass production and seed production. 2. Material and method 2.1 Places and localities of the investigations The laboratory tests and pot experiments took place in Hungary at the department of plant Pathology of Pannon University, Georgikon Faculty of Agricultural Sciences, and in Austria HBLFA Raumberg-Gumpenstein (Irdning) Research Institute for Plant Production and Agriculture, between The field experiments were conducted in the breeding and demonstration garden of the Department of Plant Science and Biotechnology of Pannon University as well as in its agrobotanical garden. From April to July we collected data and facts on the experimental fields of research Institute of HBLFA Raumberg-Gumpenstein, Irdning, Austria Laboratory investigations 34 cultivars from 22 grass species were collected for some years and beside that also seeds of five cultivated grass species from an uncultivated area and were included in the seed pathological investigations. By this seeds of 56 seed lots were tested. Two methods of seed pathological tests were used: germination test in wet chambers and of Jacobsen-method (DE TEMPE 1963; MATHUR és KONGSDAL 2003). The prescription of Hungarian Standards (MSZ 6354/3, MSZ 6354/5) were also considered in the germination tests. The assesment of 3

4 the mycological condition took place during the determination of germination power and germination rate. A 125 W Hg vapour lamp with a wavelength mainly 254 nm was used for the irradiation of Strand tall fescue seeds seeds in each of the four replications were irradiated with 0,81; 3,24; 6,48; 9,72; 12,96; 14,04, and 16,2 J/cm 2 doses Investigations in pot trials For the seed pathology tests disinfected and not disinfected seeds of Strand tall fescue were used. A Neomagnol solution of 0,5 % was made (1 tablet in 200 ml distilled water ) for seed disinfection. The pots were filled with Ramann s brown forest soil and sandy soil for the germination tests made in four replications at 20 ºC for 18 days or 10 ºC, and the plants were illuminated 12 hrs daily. During the assessment of germination rate and germination power 18 days after sowing also the biomass and length of the seedlings were measured. For the pathogenity tests conidia suspension was made from 90 g symptom-showing cock s-foot (Dactylis glomerata L.) leaves infected with Cercosporidium graminis. The infected leaves were cut into small pieces and shook in 600 ml tap water for 2 hours. After filtering the sap conidia suspension was produced of 11,2x10 3 concentration. With this suspension cock s-foot (Dactylis glomerata L.), red fescue (Festuca rubra L.), common meadow grass (Poa pratensis L.), perennial ryegrass (Lolium perenne L.) and tall fescue (Festuca arundinacea Schreb.) plantlets in pots grown in a glasshouse were inoculated Field observations and experiments Field observations were made on breeding stock material of 13 grass species and cultivars to assess their infection rates caused by Puccinia spp., Cercosporidium graminis and Ramularia pusilla. The severity of the infection was determined several times during the seasons. These were mapped and an index of severity (F i %) was calculated by the following formula: F i % = [ (a i x f i ) / (n x k)] x 100, Where: a i =range value of infection (intensity of infection), f i = the frequency of range value (frequency of infection), n = number of plants examined on the plot k = highest range value (5). 4

5 In a small plot field experiment the effect of fungal infection on yield was tested. Common meadow grass cultivars were sprayed twice (in spring and autumn) against yellow rust (Puccinia striiformis var. striiformis) and cock s-foot cultivars were sprayed against Cercosporidium graminis with the fungicides Falcon 460 EC (a.s. tebukonazol + triadimenol + spiroxamin) combined with Bravo 500 (a.s. chlorthalonil). 3. New scientific results Based on our investigations, observations and considering the literature data we propose to accept the following points as new scientific statements: 1. In Hungary we are the first who made comprehensive investigations on the occurrence and dominance relations of microscopic fungi which may contaminate seeds of 22 grass species and 34 cultivars except for red fescue, tall fescue and smooth brome. We identified 80 fungal species found on grass seed surface out of which 21 species were reported in Hungary for the first time. Beside the fungal species Alternaria alternata which is often mentioned in literature we identified and documented the presence of A. tenuissima, A. infectoria, A. chlamydospora on grass seeds. New data is the identification of two genera Ulocladium and Embellisia found on grass seeds these are related genera to the genus Alternaria. Within these genera the species Ulocladium atrum, U. botrytis, Embellisia dennisii were found. First we could proven the presence of Pithomyces chartarum on seeds of some grass species. 2. For the first time we could identify in Hungary the spreading of the following plant pathogenic fungi by grass seeds: Drechslera andersenii, D. biseptata, D. poae, Bipolaris spicifera, Curvularia inaequalis, C. lunata and Cercosporidium graminis. 3. For the first time we used UV-C irradiation of different dose to desinfect grass seeds as a possible seed treatment method. We demonstrated that far UV irradiation has a stimulating effect on the beginning of germination and shows a positive correlation to the germination rate. We could prove that this treatment has a negative effect on the external fungal contamination of seeds. 4. By data collection made on breeding stocks of several grass species we demonstrated that in the Keszthely area the curve of seasonal epidemic caused by Puccinia species has only one peak with a maximum value in September. 5. We demonstrated that the cock s-foot cultivars Keszthelyi 54 and Amba are very sensitive to the pathogen Cercosporidium graminis. Using pathogenity tests we could proven 5

6 that the fungus C. graminis isolated from cock s-foot can only infect its host and did not cause symptoms on perennial ryegrass, common meadow grass, red fescue and tall fescue. We were the first to report on damage caused by C. graminis on red fescue in Hungary. 6. In Hungary we are the first to report on damages caused by Ramularia pusilla on Lolium species and on their importance. PUBLICATIONS AND LECTURES CONNECTED WITH THE DISSERTATION PUBLICATIONS IN HUNGARIAN LANGUAGE Varga, Zs., Dongó, A. és Fischl, G. (2004): Termesztett fűfajok szemtermésén előforduló mikroszkopikus gombák. Növénytermelés, 53 (1-2): Varga, Zs. és Fischl, G. (2006): Termesztett fűfajok Cercosporidium graminis (Fuckel) Deighton okozta levélfoltossága Keszthely térségében. Növényvédelem, 42 (12): Varga Zs. és Ivány, K. (2007): Adatok a fűféléket károsító Cercosporidium graminis (Fuckel) Deighton biológiájához. XVII. Növényvédelmi Fórum, Keszthely. Összefogl Varga, Zs. (2007): Termesztett Lolium fajok ramuláriás levélfoltossága. Növényvédelem, 43 (5): Varga, Zs. és Fischl, G. (2007): Termesztett fűfajok levélfoltosság tüneteit okozó gombafajok. Gyepgazdálkodási Közlemények, 5: Fischl, G., Ivány, K., Bürgés, Gy., Varga, Zs. és Béres, I. (2007): Magfüvesek növényvédelmi technológiája. Növényvédelem, (lektorált, megjelenés alatt). LECTURES IN HUNGARIAN LANGUAGE Varga, Zs., Ivány, K. és Fischl, G. (2004): Rozsdabetegségek előfordulása termesztett fűfajokon. A gyepek változó szerepe; a gyepterületek aktuális termesztési hasznosítási és növényvédelmi kérdései című Tudományos Ülés, Keszthely. Varga, Zs. (2005): A csomós ebír (Dactylis glomerata L.) szemtermésének gombafertőzöttsége. XI. Ifjúsági Tudományos Fórum, Keszthely. CD-ROM kiadvány, Növényvédelem Szekció 615. Varga, Zs. és Fischl, G. (2005): Termesztett fűfélék szemtermésének gombafertőzöttsége. 51. Növényvédelmi Tudományos Napok, Budapest. Összefogl. 44. Varga, Zs. (2006): Újabb adatok a termesztett fűfajok gombabetegségeihez. VEAB Tudományos Ülés, Keszthely. 6

7 Varga, Zs. és Fischl, G. (2006): Termesztett fűfajok Cercosporidium graminis (Fuckl.) Deighton okozta levélfoltossága. 52. Növényvédelmi Tudományos Napok, Budapest. Összefogl. 66. Varga, Zs., Fischl, G., Ivány, K. és Valent, F. (2006): Fűfélék leveléről és száráról izolált gombafajok. XVI. Növényvédelmi Fórum, Keszthely. Összefogl Varga, Zs. (2007): Termesztett Lolium fajok ramuláriás levélfoltossága. 53. Növényvédelmi Tudományos Napok, Budapest. Összefogl. 41. PUBLICATIONS IN FOREIGN LANGUAGES Varga, Zs. and Fischl, G. (2005): Infection rates of perennial ryegrass seeds (Lolium perenne L.) with different fungi. Communications in Agricultural and Applied Biological Sciences, Ghent University, 70 (3): Nagy, P., Varga, Zs. and Fischl, G. (2005): The effect of far UV radiation on the morphology and the ability of germination of conidia of Fusarium culmorum. Cereal Research Communications, 33 (4): Varga, Zs. and Fischl, G. (2006): Pathogenic fungal species isolated from leaves and seeds of smooth brome (Bromus inermis Leyss.). Communications in Agricultural and Applied Biological Sciences, Ghent University, 71 (3b): Varga, Zs. and Fischl, G. (2006): Fungal infection of cultivated grass seeds. Cereal Research Communications, 34 (4): Varga, Zs. and Nagy, P. (2007): Effect of low dose UV-C radiation on germination rate and fungal contamination of tall fescue (Festuca arundinacea Schreb.) seeds. Acta Agronomica Hungarica, (megjelenés alatt). Varga, Zs., Krautzer, B. und Graiss, W. (2007): Samenübertragbare Pilzkrankheiten der Gräser. Der Pflanzenarzt, 3: Varga, Zs., Krautzer, B. and Graiss, W. (2007): Mycological investigations on seeds of cultivated grasses. Die Bodenkultur, (megjelenés alatt). LECTURES IN FOREIGN LANGUAGES Varga, Zs. (2006): Pathologische Untersuchungen von Gräsern und deren Samen. HBLFA Raumberg-Gumpenstein, Irdning, Ausztria. Varga, Zs., Krautzer, B. and Graiss, W. (2006): Comparative seed pathological investigations on cultivated grass species. Proceedings 4 th International Plant Protection Symposium, Debrecen PUBLICATIONS AND LECTURES ON OTHER TOPICS Varga, Zs. és Fischl, G. (2006): A pompás medinilla Glomerella cingulata okozta antraknózis betegsége Magyarországon. Növényvédelem, 43 (1):

8 Varga, Zs. és Fischl, G. (2006): A pompás medinilla új betegsége. Kertészet és Szőlészet, 55 (8): 15. Cseh, A., Varga, Zs., Taller, J., Cernák, I. és Fischl, G. (2006): Előzetes eredmények Keszthely térségi fehér fagyöngy (Viscum album L.) populációk genetikai vizsgálatairól. XVI. Növényvédelmi Fórum, Keszthely. Összefogl. 21. Varga, Zs. és Fischl, G. (2007): A szelídgesztenye penészedését okozó mikrogombák. Kertészet és Szőlészet, 56 (4): Pál-Fám, F., Keszthelyi, S. és Varga, Zs. (2007): A kukorica mikrogombái kukoricamoly (Ostrinia nubilalis Hbn.) lárvajáratokban. 12. Tiszántúli Növényvédelmi Fórum, Debrecen. Összefogl