Journal of Plant Pathology (2001), 83 (1), 63-67 Edizioni ETS Pisa, 2001 63 SHORT COMMUNICATION OCCURRENCE AND DISTRIBUTION OF FUSARIUM SPP. ASSOCIATED WITH DURUM WHEAT SEED FROM ARGENTINA G.A. Lori and M.N. Sisterna CIDEFI- CIC-Facultad de Ciencias Agrarias y Forestales, UNLP, 60 y 119, CC 31, (1900) La Plata, Buenos Aires, Argentina ABSTRACT In Argentina Fusarium head blight (FHB) caused primarily by Fusarium graminearum is an important disease of bread and durum wheat. The natural occurrence of F. graminearum and other Fusarium spp. in durum wheat seed harvested in the main cropping area was determined during the 1995-97 period. From varietal trials carried out in five locations, 192 seed of 7 cultivars and 17 lines were analyzed following the blotter test (ISTA rules). Seven Fusarium species were recovered, but F. graminearum was the only one isolated from all the. Differences in the cultivar performance among years and locations showed that the pressure of environmental conditions during anthesis would favours the disease expression. Key words: Fusarium graminearum, Gibberella zeae, head blight, scab, Triticum durum. Wheat is a widespread crop in five provinces of the temperate central-eastern zone of Argentina. Durum wheat (Triticum durum Desf.) is only grown in the southern area of the province of Buenos Aires. In the last ten years there has been a great fluctuation in the cropping area due to disease problems, the average of the last three harvests being approximately 80,000 ha. All classes of wheat and small grains are affected by Fusarium head blight (FHB), a devastating disease that can completely destroy a potentially high-yield crop. Many species of Fusarium can cause this disease but F. graminearum Schwabe is the principal pathogen in Argentina and other countries (Reis, 1988; Clear et al., 1996; Rizzo et al., 1997). Frequent rainfall, high humidity, and/or heavy dew coinciding with the flowering and early kernel-fill periods of the crop favour infection and development of the disease. In Argentina, F. grami- Corresponding author: G.A. Lori Fax: +54.221.4252346 E-mail: galori@infovia.com.ar nearum produced epidemics in the 1960s, 1970s, 1980s and 1990s (Moschini and Fortugno, 1996). For durum wheat the epidemics of 1977-78 and 1984-85 caused an important reduction in the cropping area but has increased considerably in the last years. Damage from FHB is multifold: reduced yields, discoloured, shrivelled tombstone kernels, and reduced seed quality. This disease also reduces test weight and lowers market grade. Mycotoxins are frequently associated with the growth and invasion of cereal grains by FHB fungi. The two most important mycotoxins are the estrogenic toxin zearalenone and trichothecene deoxynivalenol (Snijders, 1990; Rizzo et al.,1997). For bread wheat there are many reports about the relationship between FHB and the associated species, but in Argentina no data are available for durum wheat. The occurrence of F. graminearum and other Fusarium spp. in durum wheat seeds harvested from southern Buenos Aires province in 1995, 1996 and 1997 was determined in this work. From varietal trials carried out at Experimental Stations in five localities (Barrow, Balcarce, La Dulce, Miramar and Bordenave) in Buenos Aires Province (Fig. 1), 209 durum wheat seed of 7 cultivars and 17 lines were analyzed in 1995, 1996 and 1997 (Table 1). To determine the percentage (%) of kernel infection by F. graminearum and Fusarium spp., 200 seeds per sample were subjected to the blotter test following the ISTA rules (Neergaard, 1974) and observed after 7 days. Fusarium spp. were identified on the base of cultural features, micromorphology and conidial ontogeny according to Booth (1971). Meteorological data such as temperature, rainfall and relative humidity (RH) were registered from the weather station located nearest each experimental field. The natural occurrence of the pathogens differed according to the years and locations. F. graminearum, F. equiseti (Corda) Sacc., F. moniliforme J. Sheldon, F. oxysporum Schlechtend.: Fr., F. pallidoroseum (Cooke) Sacc (= F. semitectum Berk. and Ravenel), F. poae (Peck) Wollenweb. and F. acuminatum Ellis and Everh. were isolated but F. graminearum was the most fre-
64 Fusarium spp. in durum wheat Journal of Plant Pathology (2001), 83 (1), 63-67 Fig. 1. Buenos Aires Province : locations of durum wheat cropping area.
Journal of Plant Pathology (2001), 83 (1), 63-67 Lori et al. 65 Table 1. Cultivars and lines evaluated in different localities and years. Cultivars and lines 1995 1 1996 2 1997 2 Bonaerense Valverde + + + Bonaerense Quilacó + + + Bonaerense INTA Cumenay + + + Bonaerense INTA Facón + + + Buck Cristal + + + Buck Ambar + + + Buck Topacio + + + Buck 10 + Buck 12 + + Buck 14 + + CBW 32 + + CBW 33 + + CBW 36 + CBW 40 + + CBW 53 + CBW 54 + BF 1776 + VF 001 + VF 002 + VF 003 + VF 008 + VF 010 + + VF 012 + MAR 989 + + Total 64 85 60 1 Barrow, Bordenave, La Dulce and Miramar. 2 Barrow, Balcarce, Bordenave, La Dulce and Miramar. quent over the three years at all locations (Table 2). Also in other countries (Snijders, 1990; Bai and Shaner, 1994), several Fusaria may contribute to the head blight complex but are generally less important than F. graminearum. On the other hand, in cool climates F. culmorum predominates as the causal factor of FHB (Snijders, 1990). In Argentina as in other countries of South America (Reis, 1988), F. graminearum has been reported for many years as the main pathogen in wheat scab. This is supported by its frequency among species identified in regional surveys, chemotaxonomy grouping based on analysis of trichothecene-producing abilities of recovered isolates, and pathogenicity studies (Lori et al., 1992; Galich, 1996). Infection levels of F. graminearum were variable especially according to the year. In 1997 the means were higher than in 1995 and 1996. Although none of the varieties and lines were free of F. graminearum infection, contamination values were related to environmental conditions. According to Moschini and Fortugno (1996) the meteorological conditions have an influence from the beginning of heading to early grain development. Factors such as RH affect F. graminearum infection and fungal invasion. In 1997 from Balcarce and Miramar reached a high percentage of infection (15.12 and 22.54 respectively). In these locations the heading period coincided with RH values higher than 90% (96 and 95, respectively). Love and Seitz (1987) stated that F. graminearum grows ideally at or above 92-94% RH. In contrast contamination showed low levels in the three years recorded in Bordenave where the combination of sandy soil and dry climate (68% mean RH during heading) does not favour F. graminearum infection. In Argentina, cultivars are classified as susceptible to moderately susceptible. Our results do not show differences among genotypes except for Buck Topacio that was less affected than the other cultivars. This particular behaviour could be due to heading at a period unfavourable to infection. Compared to F. graminearum the other Fusarium spp. had a very low frequency and were variably distributed over the years (Table 3). F. poae which was found in a small number of wheat is known to be an important producer of the trichothecene group A mycotoxins. It has been reported on oat seed more often than on seed of other cereals in other regions (Clear et al., 1996). In our country it was recently recorded on barley (personal communication) causing spots in sheaths and grains. In Argentina FHB due to Fusarium spp. and especially to F. graminearum can seriously contaminate the kernels of durum wheat grain when meteorological conditions are favourable. The probable presence of mycotoxins in the finished wheat products can in this case be a potential risk to humans. ACKNOWLEDGEMENTS The authors acknowledge financial support from Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Industrias Fideeras Argentinas.
66 Fusarium spp. in durum wheat Journal of Plant Pathology (2001), 83 (1), 63-67 Table 2. Infection levels of F. graminearum (%), in different localities and years. Localities F. graminearum (% infection) no. of 1995 no. of 1996 no. of 1997 Localities means Balcarce ND ND 17 12 12.690 Maximum 22.500 24.500 Minimum 0.500 5.500 Mean 10.260 15.120 Barrow 16 17 12 1.720 Maximum 1.000 0.500 10.000 Minimum 0.000 0.000 1.000 Mean 0.250 0.029 4.910 Bordenave 16 17 12 0.220 Maximum 0.000 1.000 0.500 Minimum 0.000 0.000 0.000 Mean 0.000 0.520 0.160 La Dulce 16 17 12 1.480 Maximum 3.000 1.000 6.000 Minimum 0.000 0.000 1.500 Mean 0.780 0.230 3.450 Miramar 16 17 12 7.700 Maximum 3.500 1.500 42.000 Minimum 0.000 0.000 8.500 Mean 0.210 0.350 22.540 Total 64 85 60 Mean 0.310 2.270 9.230 ND: no data. Table 3. Natural occurrence of Fusarium spp. in 1995, 1996 and 1997. Fusarium spp. 1995 1996 1997 F. graminearum 17/64 1 ( 0 3.5) 2 40/85 (0-22.5) F. equiseti 5/64 (0 2) F. moniliforme 1/64 F. oxysporum 0 5/85 (0 1) 52/60 (0 42) 0 2/60 (0.5 1) 0 0 6/60 F. poae 0 0 3/60 F. acuminatum 0 0 1/60 (0 0.5) F. pallidoroseum 0 1/85 0 1 no. of with presence of spp./total number of. 2 range of infection (%). REFERENCES Bai G., Shaner G., 1994. Scab of wheat: prospects for control. Plant Disease 78: 760-766. Booth C., 1971. The genus Fusarium. Commenwealth Mycological Institute. Kew, Surrey, England. Clear R.M., Patrick S.K., Platford R.G., Desjardins M., 1996. Occurrence and distribution of Fusarium species in barley and oat seed from Manitoba in 1993 and 1994. Canadian Journal of Plant Science 18: 409-414. Galich M.T.V., 1996. Fusarium head blight in Argentina. In: Dubin H.J., Gilchrist L., Reeves J., McNab A. (eds.). Proceedings of the Workshop Fusarium Head Scab: Global Status and Future Prospects Held at CIMMYT, México 1996, 19-28. Lori G.A., Carranza M.R., Violante A., Rizzo I., Alippi H.E., 1992. Fusarium spp. en trigo, capacidad toxicogénica y quimiotaxonomía de las cepas aisladas en la Argentina. Agronomie 12: 459-467.
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