PATHOGENICITY OF DRECHSLERA AVENAE (EIDAM) SCHARIF TO SELECTED OAT GENOTYPES (AVENA SATIVA L.)

Małgorzata Cegiełko
Phytopathology Department, University of Agriculture in Lublin, Poland

ABSTRACT

Investigations with artificial inoculation of soil and grain of 12 oats genotypes with Drechslera avenae isolate no 1 were carried out in years 2000-2002 on experimental plots near Zamość. In each year the number of 7-weeks seedlings, number of plants and panicles before harvest, and grains yield from the individual plot were calculated. The greatest mean seedling loss after three years of investigations when compared to the control was 47.8% (‘Akt’), and the lowest 13.0% (‘Bajka’), while the loss of plants before harvest ranged from 15.8% (‘Bajka’) to 52.6% (‘Bachmat’). The mean decrease in panicle number compared to the control ranged from 4.2% (‘Bajka’) to 45.5% (‘Jawor’) and mean grain yield loss was lowest in ‘Borowiak’ (18.4%) and ‘Bajka’ (22.8%), while highest in ‘Akt’ (70.3%). Mycological analysis of grains obtained from oat plants developed from caryopses subjected previously to artificial infection with Drechslera avenae under field conditions revealed a considerable number of this pathogen isolates. On average isolates of Drechslera avenae accounted for 59.0% of the total number of fungi isolated from surface-sterilized grains and 48.7% from non-sterilized grains. From both surface-sterilized and non-sterilized control grains, most frequently were isolated: A. alternata, B. sorokiniana, F. culmorum, F. graminearum, F. oxysporum, F. poae, F. sporotrichioides and P. verrucosum var. cyclopium.

Key words: oat, Drechslera avenae, pathogenicity, genotypes.

INTRODUCTION

Oat, in spite of its natural protective barrier in rhizosphere due to the presence of saponins in the root system and leaves in the glycoside form [21,31], just like other cereals is infected by fungi damaging the roots, straw base, leaves and panicles [9,17,19,26,30].

Drechslera avenae belongs to specialized pathogens infecting various oat species (Avena spp.) and occasionally species of some grasses [4,6,8,13,16,20,25,32,33]. Species Drechslera avenae occurs universally in the majority of oat cultivation. It may be a cause of black root rot and leaf spot disease but only sporadically causes epidemics [13,30]. This fungus was found in the U.S.A. and Canada [13] and in Argentina and Brazil [25]. It has also been heard about the occurrence of Drechslera avenae in oat cultivation in Europe [2,7,18].

Species D. avenae settles in oat glume and caryopsis [6,20] and embryo [8]. Spreading of D. avenae takes place through the mycelium located in the testa and inside the lemma and palea. Mycelium of D. avenae may live up to ten years in stored grains [30].

Species Drechslera avenae shows an ability to form secondary metabolites such as: pyrenophorol, pyrenophorin, or dihydropyrenophorin [3,16,37] as well as anthraquinone derivatives – cynodontin and helminthosporin [12].

Scarce information in national literature on the pathogenicity of Drechslera avenae in relation to oat and proven unlike susceptibility of the cultivars of different species of cereals to infections by Drechslera spp. [23,40], suggested the possibility of similar differentiation also in the case of oat genotypes.

MATERIAL AND METHODS

The present research were carried out in years 2000-2002 on experimental plots near Zamość on brown, leached, loess like soil where tuber crops were forecrop. Every year the recommended fertilization NPK doses [24] and manual weed control were applied. The investigations included 12 oat genotypes (‘Akt’, ‘Bachmat’, ‘Bajka’, ‘Bohun’, ‘Borowiak’, ‘Cwał’, ‘Jawor’, ‘Polar’, CHD 2099, STH 4298, STH 4599, STH 4699) and isolate Drechslera avenae no 1 singled out from oat grains, which in laboratory tests carried out using the Mishra and Behr method [27] showed the greatest pathogenicity.

The experiment was set up using the fully randomized block method. In each year the experiment included a block with plots sowed with grains and bedding artificially infected by D. avenae and a block with control plots without grain and bedding artificial infection. 100 grains of each cultivar or breeding line were sown in four reps on plots with the area of 1.25 m² (2.5 x 0.5 m) (25 caryopses were sown in a row with a 10-cm-long distance).

In a laboratory 24 hours before the sowing, well-developed oat grains, with no symptoms of sickness and surface-sterilized (for 1 min in 50% C₂H₅OH and for 1 min in 0.1% HgCl₂) were infected by suspension of D. avenae spores (6 x 10⁴ conidiums in 1 ml sterile distilled water). Sterilized caryopses were submerged individually in unsolidified agar maltose nutrient solution (a ready-made product by Difco) and put into Petri dishes. A drop of D. avenae conidiums suspension was put on grains covered with a layer of nutrient solution with an automatic VE-100 pipette, and drops of sterile distilled water were put on the control grains also covered with a layer of nutrient solution. Grains were sown individually in 3-cm-deep holes, into which infective material prepared according to the Nol’s method [22] was introduced. The control grains were put in holes and covered with regular soil instead of infective mixture.

During the vegetation period, the number of 7-week-old seedlings as well as plants and panicles was determined before the harvest on individual plots. After the harvest, the grain yield from the plot was determined. The obtained results were verified with the Tukey test [41], applying the 3-way model (genotype, fungus, year of studies).

Mycological analysis of grains obtained from the plants grown from caryopses artificially infected by D. avenae and from the control was carried out on maltose nutrient solution (bioMérieux) with an addition of streptomycin (1 mg·dm^-3). For every genotype from the particular combinations of the experiment, 100 grains were analyzed (50 non-sterilized and 50 sterilized for 1 min in 50% C₂H₅OH and for 1 min in 0.1% HgCl₂). The grains put in Petri dishes were kept in a thermostat for 8 days at 22°C. Fungus colonies grown after that time were split off slantwise. For the marking of fungi species monographies and keys by Booth [5], Domsch et al. [10], Ellis [11], Gilman [15], Munk [28], Nelson et al. [29], Ramirez [34], Rifai [36], and Thom and Raper [38] were used.

2000 vegetation period was characterized by higher than the multi-year average temperature in April, May, June, July, and August (from 0.4 to 4.3°C) and higher than multi-year average precipitation in April, May and June. During vegetation period 2001 temperature was higher than the multi-year average by 0.7 to 3.7°C. In 2001 only in April and July the percentage of the precipitation norm exceeded the multi-year average, respectively by 27.9 and 56.8. In vegetation season 2002 the temperature was higher comparing to the multi-year average from 1.9°C in April and June to 4.6°C in May. The percentage of the precipitation norm was higher from the multi-year average in May, June, and July, respectively by: 41.7, 69 and 2.52 (Table 1).

RESULTS

In each year of the investigations a decrease in the number of plants grown from oat caryopses artificially infected by the studied isolate D. avenae no 1 was noted (Table 2). The greatest mean seedling loss as a result of D. avenae infection compared to the control equaled 47% (‘Akt’), and the smallest 13% (‘Bajka’). Significant differences in the number of seedlings compared to the control were found in 7 oat genotypes in 2000, 5 in 2001 and 7 in 2002.

Mean decrease in the number of plants before harvest compared to the control as a result of artificial infection of oat caryopses by D. avenae strain no 1 ranged from 15.8% for ‘Bajka’ to over 50% in ‘Akt’ (51.1%) and ‘Bachmat’ (52.6%) (Table 3). Significant differences in the number of plants before the harvest in 2000 compared to the control were found in six oat genotypes, in 2001 in two genotypes, and in 2002 in six genotypes. After three years of investigations, significant differences in the number of plants before harvest compared to the control were found in two oat genotypes (‘Bachmat’, STH 4298).

Decrease in the number of panicles compared to the control ranged from 4.2% in ‘Bajka’ to 45.5% in ‘Jawor’ (Table 4). Significant differences in the number of panicles compared to the control were found in four oat genotypes in 2000 and in ‘Akt’ in 2001.

Statistical analysis of the results from three years of investigations into grain yield showed significant differences in the grain yield compared to the control in ‘Akt’ (Table 5). In 2000, significant differences in the yield between the combination with artificial infection of the caryopses and the control were found in six oat genotypes, in 2001 in three genotypes, and in 2002 in eight genotypes. The lowest percentage decrease in grain yield compared to the control was 18.4% in ‘Borowiak’ and 22.8% in ‘Bajka’. Over 60% decrease was found in genotypes: ‘Akt’, ‘Bachmat’, ‘Jawor’ and CHD 2099 (Fig. 1).

As a result of the mycological analysis of grains obtained in 2000-2002 from oat plants grown from caryopses artificially infected by D. avenae strain no 1, 1287 isolates of fungi from sterilized grains and 1330 isolates of fungi from non-sterilized ones were obtained (Table 6). On average D. avenae isolates accounted for 59.0% of the colonies grown from sterilized grains and 48% from non-sterilized grains (Fig. 2). This fungus was more often obtained from non-germinating grains. In each year of the investigations, significant quantities of the following species were obtained: Alternaria alternata, Bipolaris sorokiniana, Fusarium sporotrichioides, and Penicillium verrucosum var. cyclopium.

As a result of the mycological analysis of grains obtained from control plants of the studied oat genotypes 928 fungi isolates from sterilized caryopses and 1362 isolates from non-sterilized caryopses (Table 7) were singled out. From both sterilized control as well as from non-sterilized caryopses most often were isolated: A. alternata, B. sorokiniana, F. culmorum, F. graminearum, F. oxysporum, F. poae, F. sporotrichioides, and P. verrucosum var. cyclopium.

DISCUSSION

The results of the investigations in years 2000-2002 in the region of south-east Poland show that Drechslera avenae was a cause of seedling black root rot in oat that occurred in every vegetation season. This pathogen also played a significant economic role in damaging oat seedlings and leaves in the United States and Canada [8,13]. Weather conditions in 2002 turned out to be the most advantageous to D. avenae infections because humid and warm weather. To such conditions as the most advantageous to D. avenae development and oat seedling infections by this fungus points Obst [30].

In the case of seedling infections, the major criterion for the assessment of susceptibility of oat cultivars and breeding lines to D. avenae was the decrease in the plant number as a result of seedling black root rot pre- and after-germination. The fungus D. avenae introduced to the grain surface and into the soil in the form of infective mixture assured close contact between the pathogen and the plants of particular oat genotypes. Taking into account changing strain virulence within the Drechslera type fungi [1,14], for the filed investigations, strains of verified pathogenicity were applied using the Mishra and Behr method [27]. The decrease in number of plants on the experimental plots in the case of D. avenae infections resulted mainly from seedling necrosis in the first 7 weeks from the sowing of artificially infected grains. During the subsequent growth single plants died, and therefore there was a difference between the number of plants set during both inspections. For the assessment of genotype susceptibility, a decrease in the number of seedlings, plants and panicles before the harvest as well as the grain yield from the experimental area were analyzed.

Assuming a 50% plant decrease before the harvest and an over 48% decrease in grain yield from the experimental area, on average after three years of investigations, ‘Akt’ and ‘Bachmat’ were recognized as the most susceptible to D. avenae infections while in ‘Bajka’ and ‘Borowiak’ the smallest average plant number decrease, not surpassing 30% and a grain yield decrease slightly surpassing 40% were found.

A great number of isolates of D. avenae obtained from the sowing material originating from plants obtained from caryopses artificially infected by this species points out to the grain as a significant source of infection for plants grown from it. About the increase in the significance of D. avenae for infecting oat grains cultivated in Canada informs Clear et al. [8]. In Poland the existence of D. avenae on oat grain from natural infections was noted by Truszkowska et al. [39].

Surface grain sterilization only partly eliminated D. avenae, which indicates a close contact of this fungus with grain and inhabiting the inside of caryopses. Obtaining D. avenae in a greater percentage from non-germinating caryopses proves that this pathogen is a cause of a reduction in germination ability of oat caryopses.

Application of maltose solution with an addition of streptomycin for the isolation of D. avenae from the oat grain turned out to be effective and allowed obtaining many isolates of this fungus. In addition to maltose solution, for the isolation of D. avenae from infected oat caryopses also osmotic method, breeding on Reis’ solutions an oat agar, as well as the method with the application of increased temperature are recommended [20,35].

CONCLUSIONS

1. For the studied oat cultivars and breeding lines no occurrence of genotypes fully resistant to seedling infection by Drechslera avenae was found.

2. Oat grain infection by Drechslera avenae may inform about an increase in seedling black root rot, although weather conditions had an influence on the occurrence of seedling black root rot.

3. Oat ‘Bajka’ may be recommended as test cultivar in investigations into oat susceptibility to Drechslera avenae infections because its resistance to this pathogen was a recurrent quality.

4. Cultivar ‘Akt’ was of the higher susceptibility to Drechslera avenae infection.

REFERENCES

1. Arabi M.I., Barrault G., Sarrafi A., Albertini L., 1992. Variation in the resistance of barley cultivars and in the pathogenicity of Drechslera teres f. sp. maculata and D. teres f. sp. teres isolates from France. Plant Pathol. 41, 180-186.

2. Aresnijević M., Draganić D., Kenzević T., 1996. Verste nekadasnjeg roda “Helminthosporium” utvrdene u Jugoslaviji [Species of previous genus Helminthosporium detected in Jugoslavia]. Zastita bilja 47(2), 93-119.

3. Barco A., Benetti S., De Risi C., Pollini G.P., Zanirato V., 1995. A [3+2] nitrile oxide cycloaddition approach to (-)- pyrenophorin, and rosefuran. Tetrahedron 51(28), 7721-7726.

4. Bocchese C.A.C., Martinelli J.A., Matsumura A.T.S., 2001. Specificity of Pyrenophora avenae for grain tissues of Avena sativa and its enzymatic activity. Fitopathol. Bras. 26(2), 180-184.

5. Booth C., 1971. The genus Fusarium. Comm. Mycological Institute Kew, Surrey England.

6. Carmona M.A., Zweegman J., Reis E.M., 2004. Detection and transmission of Drechslera avenae from oat seed. Fitopathol. Bras. 29(3), 319-321.

7. Cegiełko M., 2002. Wstępne badania nad podatnością genotypów owsa (Avena sativa L.) na Drechslera avenae (Eidam) Scharif. [Introductory investigations into oat (Avena sativa L.) genotypes susceptibility to Drechslera avenae (Eidam) Scharif.]. Ogólnopolska Konf. Nauk. Perspektywy rozwoju ochrony roślin w Polsce w XXI wieku. Zesz. Nauk. AR w Krakowie, Rolnictwo 82, 55-58 [in Polish].

8. Clear R.M., Patrick S.K., Gaba D., 2000. Prevalence of fungi and fusariotoxins on oat seed from western Canada, 1995-1997. Can. J. Plant Pathol. 22, 310-314.

9. Cunfer B.M., 2000. Stagonspora and Septoria diseases of barley, oat and rye. Can. J. Plant Pathol. 22, 332-348.

10. Domsch K.H., Gams W., Anderson T.H., 1980. Compendium of soil fungi. Academic Press London, New York, Toronto, Sydney, San Francisco.

11. Ellis M.B., 1971. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew Surrey, England.

12. Engström K., Brishammar S., Svensson Ch., Bengtsson M., Andersson R., 1993. Anthraquinones from some Drechslera species and Bipolaris sorokiniana. Mycol. Res. 97(3), 381-384.

13. Frank J.A., Christ B.J., 1988. Rate limiting resistance to Pyrenophora leaf blotch in spring oats. Phytopathol. 78(7), 957-960.

14. Gacek E., 1979. Badania nad odpornością jęczmienia na plamistość siatkową powodowaną przez Pyrenophora teres (Died.) Drechsl. [Investigations into barley resistance to leaf net disease caused by Pyrenophora teres (Died.) Drechsl.]. Hod. Rośl. Aklim. Nasienn. 23(2), 73-83 [in Polish].

15. Gilman J.C., 1957. A manual of soil fungi. The Iowa State College Press-Ames, Iowa, USA.

16. Kastanias M.A., Chrysayi-Tokousbalides M., 1999. Comparative phytotoxicity of pyrenophorin and pyrenophorol isolated from a Drechslera avenae pathotype. Brighton crop protection conference: Weeds. Proc. Inter. Conf., Brighton, UK, 2, 581-582.

17. Kiecana I., 1998. Występowanie Fusarium spp. na owsie (Avena sativa L.) [Occurrence of Fusarium spp. in oat (Avena sativa L.)]. Post. Ochr. Rośl. 38(2), 541-543 [in Polish].

18. Kiecana I., Kocyłak E., 1999. Pathogenicity of Fusarium spp. on oats seedlings (Avena sativa L.). Plant Breed. Seed Sci. 43(1), 91-99.

19. Kiecana I.,. Mielniczuk E., Cegiełko M., Pszczółkowski P., 2003. Badania nad chorobami podsuszkowymi owsa (Avena sativa L.) z uwzględnieniem temperatury i opadów [Investigations into oat (Avena sativa L.) stem base diseases considering temperature and precipitation]. Acta Agrobot. 56(1-2), 95-107 [in Polish].

20. Lângaro N.C., Reis E.M., Floss E.L., 2001. Detection of Drechslera avenae in oat seeds. Fitopathol. Bras. 26(4), 745-748.

21. Lüning H.U., Schlösser E., 1976. Saponine in Avena sativa. Angew. Botanik 50, 49-60.

22. Łacicowa B., 1964. Badania mikoflory materiału siewnego pszenicy uprawianej na obszarze woj. lubelskiego, uwzględniające szczególnie grzyby patogeniczne [Investigations into mycoflora of the sowing material of wheat cultivated in Lubelskie province, taking into account particular pathogenic fungi]. Ann. Univ. Mariae Curie-Skłodowska, Agricultura 19 E, 381-406 [in Polish].

23. Łacicowa B., Pięta D., 1991. Podatność różnych odmian jęczmienia jarego na porażenie przez Drechslera sorokiniana (Sacc.) Subram. et Jain. [Susceptibility of different varieties of barley to infections by Drechslera sorokiniana (Sacc.) Subram. et Jain.]. Hod. Rośl. Aklim. Nas. 35(5/6), 53-59 [in Polish].

24. Mazurek J., Mazurek J., Król M., 1993. Wpływ odmiany gleby i agrotechniki na plonowanie owsa [Influence of soil variety and agronomic practices on oat yielding]. [W:] Biologia i agrotechnika owsa. IUNG Puławy, 247-308 [in Polish].

25. Mehta Y.R., 2001. Molecular and pathogenetic variability of Drechslera isolates form oats. Fitopathol. Bras. 26(3), 590-596.

26. Mielniczuk E., Kiecana I., Perkowski J., 2004. Susceptibility of oat genotypes to Fusarium crookwellense Burgess, Nelson and Toussoun infection and mycotoxin accumulation in grains. Bratislava, Biologia 59(6), 809-816.

27. Mishra C.B.P., Behr L., 1976. Der Einfluss von Fusarium culmorum (W.G. Sm.) Sacc., Fusarium avenaceum (Fr.) Sacc. und Fusarium nivale (Fr.) Ces., Griphosphaeria nivalis Müller et Arx auf die Keimung des Weixen. Arch. Phytopatol. Pflanzenschutz 12(6), 373-377.

28. Munk A., 1957. Danish Pyrenomycetes. A. Preliminary Flora. Copenhagen Ejnar Munksgaard.

29. Nelson P.E., Toussoun T.A., Marasas W.F.O., 1983. Fusarium species. An Illustrated Manual for Identification. The Pennsylvania State University Press University Park and London.

30. Obst A., 1995. Seedling blight and leaf spot of oats caused by Drechslera avenae. [In:] Helminthosporia metabolites, biology, plant diseases Bipolaris, Drechslera, Exserohilum. Ed. J. Chełkowski, 161-174.

31. Osbourn A., 1996. Saponins and plant defense – a soap story. Trends Plant Sci. 1, 4-9.

32. Paul V.H., 1995. Grass diseases caused by Drechslera spp. [W:] Helminthosporia metabolites, biology, plant diseases Bipolaris, Drechslera, Exserohilum. Ed. J. Chełkowski, 175-186.

33. Prończuk M., 2000. Choroby traw – występowanie i szkodliwość w uprawie na nasiona i użytkowaniu trawnikowym [Grass diseases – occurrence and harmfulness in cultivation for seeds and lawn use]. Rozpr. Nauk. IHAR, Monografie 4 [in Polish].

34. Ramirez C., 1982. Manual and atlas of the Penicillia. Elsevier Biomedical Press. Oxford.

35. Reis E.M., Reis A.C., Casa R.T., Blum M.M.C., 1999. Comparison of methods to detect leaf and head blighting fungi in small grain seeds. Summa Phytopathologica 25, 364-367.

36. Rifai M.A., 1969. A revision of the genus Trichoderma. Kew Surrey, England.

37. Sugawara F., Strobel G.A., 1986. (-) – Dihydropyrenophorin, a novel and selective phytotoxin produced by Drechslera avenae. Plant Sci. 43, 1-5.

38. Thom Ch., Raper K.B., 1945. A manual of the Aspergilli Baltimore. The Williams & Wilkins Company.

39. Truszkowska W., Dąbrowska J., Dorenda M., Kita W., Pląskowska E., 1988. Choroby powodowane przez grzyby występujące w mieszance pastewnej owsa (Avena sativa L.) z peluszką (Pisum arvense L.) [Diseases caused by fungi occurring in oat (Avena sativa L.) and field pea (Pisum arvense L.) fodder mixture]. Rocz. Nauk Rol. 18 E (2), 95-107 [in Polish].

40. Wakuliński W., 2004. Reakcja form ozimych Triticum aestivum L. i x Triticosecale Wittmack na porażenie przez Pyrenophora tritici – repentis (Died.) Drechsler oraz charakterystyka wybranych cech z zakresu biologii patogena [Reaction of winter forms of Triticum aestivum L. and x Triticosecale Wittmack to infection by Pyrenophora tritici – repentis (Died.) Drechsler and characteristics of chosen pathogen biology features]. Wyd. SGGW Warszawa, Rozpr. Nauk. i Monografie 281 [in Polish].

41. Żuk B., 1989. Biometria stosowana [Applied biometry]. PWN Warszawa [in Polish].

Accepted for print: 27.03.2008

Responses to this article, comments are invited and should be submitted within three months of the publication of the article. If accepted for publication, they will be published in the chapter headed 'Discussions' and hyperlinked to the article.