V01.4:407^t18. Annual variations in the microflora of some varieties of Finnish malting barley Tapani Tuomi and Heikki Rosenqvist Helsinki University of Technology, Department of Chemical Engineering, Laboratory ofBiochemistry and Microbiology, FIN-02150 Espoo, Finland. Three major Finnish malting barley varieties were studied for annual variations in the incidence of seed-derived fungi, bacteria and actinomycetes. In 1990-1992, 114 characterized fungal, 59 unchar- acterized bacterial and 12 uncharacterized actinomycetal isolates were extracted from samples of seed intended for use in malting. When the yield of the plant hormone, indole-3-acetic acid (lAA), from enriched microbial cultures was weighed against the microbial biomass and the endogenous lAA concentration of the barley harvests, it was concluded that potential exists for bacterial lAA production in biologically signifi- cant amounts, given some minor annual variations. As expected from the average rainfall and temperature during the growing season, microbial counts in all cultivars were highest in 1992. Most of the fungal species found were of saphrophytic charac- ter, and field fungi were dominant in the samples. On the whole, microbial counts and spectra in all samples confirmed that each harvest of all cultivars was of good vigour and well suited for malting purposes. Strains of plant pathogenic character included species of Septoria nodorum (Berk) Berk, Drechlera teres (Sacc) Subraim & Jain, D. sorokiniana (Sacc) Subram & Jain and D. graminea (Rab.) Shoem. A consistent difference was noted in the microbial infection severities of the cultivars. Key words: Hordeum vulgare, plant-microbe interactions, indole-3-acetic acid Abbreviations: cfu, colony-forming units; lAA, indole-3-acetic acid ntroduction A wide range ofbacteria, yeasts and moulds col- onize the surface and outer layers of mature bar- ley kernels both in the field and during storage (Briggs 1978, Flannigan 1974). Germination in moist soil exposes the grain to an additional spec- trum of microorganisms under conditions favour- able for microbial growth. Penetration of micro- organisms is usually arrested by cuticularized layers and highly lignified walls of the surface layers of the grain. Microbial growth appears to extend to the testa-nucellar cuticle, which acts as a barrier to further penetration. However, these mechanical barriers to microbial invasion may © Agricultural Science inFinland Manuscript received January 1995 407 AGRICULTURAL SCIENCE IN FINLAND https://www.c-info.fi/en/info/?token=XQuRHeDDdEdNS3F4.UBvRpHdIezZ6An7KLIQURQ.y8U2BxguBrWfHtnS1bPEpTPIO8o4s6a9ZowsJdeANLxTANwLf5nwZXLyP0r1DFWBkc2uH5_A_jdCEWPouIQeeeYrUUQqI6Q3EYR6BIvtZF3InLW0HWaykE6yomqApyyy7OEUlHO0wL4k-o7Y77xjf8d6-CBWZ2Ab_aA-OtRfNyQRP70NmCnYTK62J5035O6lMLaj6zbm4XZxTHib4uP8QHIZfYxERhRnwHYF9d5PcCJVaszOjoQcP_ty7HMBsqDC3hdYMyMcOo53-bXOKP0lWl0xhyTDvXGp_w Tuomi, T. & Rosenqvist, H.: Fungi and bacteria in malting barley be weakened when grains crack during drying or harvesting or when the surface layers soften at the high moisture contents required for ger- mination (Briggs 1978). Microflora associated with the grain can cause gushing of undesirable flavours in beer and produce harmful mycotox- ins (Amaha and Kitabatake 1981, Chelkowski 1991). These microbes influence the enzymatic activity of wetted grain and alter the quality of malted grain, and on several occasions microbi- al activity has been noted to interfere with ger- mination (Briggs and McGuinness 1992). Much remains to be learnt about the mecha- nisms of microbial action on cereals. In normal circumstances, microbialproduction ofenzymes such as P-glucan solubilase(Yin et al. 1989) and cellulases (Hoy et al. 1981) is of importance, as are reduced oxygen contents due to microbial activity (Doran and Briggs 1993). One factor that tends to have been overlooked is the microbial production of the plant hormones that influence the germination and growth of the grain. In plants, absolute and relative levels of hormones are instrumental in controlling phenomena such as growth, differentiation, structural organisation and passage from the vegetative to the reproduc- tive phase, as well as other developmental and dynamic events. The effect of endogenous hor- mone gradients on plants can often be mimicked by applying hormones to plants externally, and thus also by microbes producing and excreting hormones (Davies 1990, Gogola 1991, Haahtela et al. 1990, Loper and Schroth 1986, Rademacher 1992, Rademacher and Graebe 1979,Serrada et al. 1982). Microbe-derived plant hormones of potential interest for the development, germination and growth of barley kernels include compounds from all main classes of plant hormones, but only bacterial indole-3-acetic acid (lAA) has been estimated to occur in amounts of any significance (Tuomi et al, 1994, 1995). In screening barley grain for microbial lAA production, we previ- ously used three Finnish malting grade barley cultivars of the 1990 harvest. As would be ex- pected, the microbial population of barley var- ies not only from cultivar to cultivar, but also from year to year. In an effort to see how our results hold up to annual variations in the mi- crobial flora, we in the present study examined variations in the incidence of bacteria, and also of fungi and actinomycetes, in the same three malting barley cultivars in 1990, 1991 and 1992. Our main objective was to evaluate the annual variability in microbial plant hormone produc- tion in barley, but in doing so we concurrently acquired additional information on the variations in the microbial spectra and counts of barley. Previous investigations have given us a good picture of the spectra of epiphytic moulds on the roots, stem bases and leaves of Finnish barley (Mäkelä 1972, 1977 a,b, Mäkelä and Mäki 1980, Mäkelä and Parikka 1980). Less is known, how- ever, about the seed-borne fungi of malting bar- ley, and the few studies that have been published on this subject have used a different methodolo- gy and different barley varieties from us (Haikara et al. 1977, Ylimäki 1970, 1981). As a result, several species not heretofore reported in Finn- ish barley seeds are introduced here, while at the same timemany previously encountered species were not found. Since our findings complement the overall picture of the mycoflora of Finnish barley grain, we focus on the general microbiol- ogy of the barley samples, which is of interest to all those involved with the processing and cul- tivation of Finnish barley varieties. Barley plants grown in temperate, humid re- gions are parasitized by about ten economically harmful bacterial and fungal foliar pathogens, some of which also attack parts other than foli- age. Except for rusts and powdery mildew, most of the foliar-attacking parasites, as well as many of the pathogens causing diseases in roots, are seedborne, and kernel infections frequently dis- colour kernels and cause loss of quality and crop value (Kiesling 1985, Mathre 1982). All barley foliar pathogens with the exception of rusts have associations with infected crop refuse from pre- vious barley crops. The importance of infected seed in the disease cycle is inversely proportional to the amount of inoculum produced from in- fected crop refuse. When cultural practices in- volving little or no tillage and monoculture are 408 AGRICULTURAL SCIENCE IN FINLAND Vol. 4: 407^18. combined, the new crop may have extremely high inoculum potential. Under favourable climatic conditions this may cause severe early outbreaks of foliar diseases on plants in the first of the four leaf stages (Kiesling 1985). With this in mind - and since the data were at hand - we also look briefly at the pathogenicity of the isolated spe- cies, and on the incidence of plant pathogenic species amongst the seeds of different cultivars from harvest to harvest. Material and methods Barley samples Dry (moisture content ca. 8 wt %), making-grade grains of the cultivars Kymppi, Kustaa and Hjan Pokko were used. These cultivars are among the four most important barley varieties used by Finnish malt producers (cv. Kilta being the fourth). Kymppi is a two-rowed variety that is also used as fodder (since 1987). Kustaa (mar- keted in 1980) is reasonably good in yield and has a shorter growing season than other two- rowed barley varieties cultivated in Finland. Hjan Pokko (introduced in 1980) is a multi- rowed variety that gives high yields and is well suited to the production of high-enzyme-content malt (Lampinen 1989). Fungi and bacteria were isolated from all three cultivars of the 1990, 1991 and 1992 har- vests. The samples were taken directly from a malting plant as soon as the new harvests be- came available. Microbes were isolated within one year of harvesting in 1991-1993. Five par- allel plates were prepared at each isolation and enumeration step. Isolation and enumeration of fungi and bacteria Fungi, other than Fusaria , and bacteria were iso- lated from spread plates prepared from milled (Frithsch Pulverisette 14, sieve size 0.5 mm) grains suspended in physiological salt solution. Potato dextrose agar (PDA, Biokar Diagnostics) containing 0.5 g/litre ampicillin was used for iso- lating the fungi, and Plate-count agar (Merck) with 0.01 g/litre cycloheximide for isolating the bacteria. Fungi were inoculated in both daylight and under near-UV radiation from a black light (Philips, TLD 36W/08) with a 12 h light-dark cycle to induce sporulation. To distinguish iso- lates, fungi were grown on Malt extract (Merck), Czapek-Dox (Oxoid) and Wort (Difco) agars, as well as on PDA, in both darkness and light. Viable counts offungi and bacteria in grains were calculated from dilution plates. Fusarium spp. failed to show up on spread plates and were thereforeisolated by direct plat- ing of kernels on Modified Czapek-Dox agar containing iprodione and dichloran (CZID me- dia) according to the method described by Abildgren et al. (1987). Plated kernels were in- cubated under a daylight lamp (Sylvania, 36W Activa 172). Fungal isolates were identified at the Centraalbureau voor Schimmelcultures in Baarn, The Netherlands. Isolates belonging to the same species were treated separately if they had been isolated from different cultivars. The percentage ofkernels contaminated with isolates served as a quantitative measure of Fusarium contamination. Actinomycetes were isolated and enumerat- ed on spread plates prepared on Starch-casein agar (10 g/l soluble starch; 0.3 g/1 casein; 2.0 g/I KNO s; 2.0 g/l NaCI; 2.0 g/l K,HP0 4; 0.05 g/l MgSQ 4 x 7H 20; 0.02 g/l CaCO,; 0.01 g/l FeS0 4 x 7H,0; 15.0 g/l Bacto agar, Difco), con- taining 0,0125 mg/ml cycloheximide, as de- scribed by Rand et al. (1976). Analysis of lAA The lAA content of barley grain was analysed according to the method described by Tuomi and Rosenqvist (1995). The method involves purifi- cation by solvent partitioning and thin layer chro- matography, preparation of trimethylsilyl deri- 409 AGRICULTURAL SCIENCE IN FINLAND Tuomi, T. & Rosenqvist, H.: Fungi and bacteria in malting barley Table 1.Variations inaverage rainfall and temperatures (T) in the 1990-1992growing seasons. Values have been summed over cultivation regions I and II as covered by Mustonen et al. 1994, and summed values divided by the number of observation points to get average values forcombined cultivation regions I and 11. Data from The Finnish Meteorological Institute. Period 1990 1991 1992 Rainfall T Rainfall T Rainfall T (mm) (C°) (mm) (C°) (mm) (C°) 01.05- 9 9 12 7 4 11 31.05- 5 15 12 12 7 16 30.06- 16 16 17 17 26 16 30.07- 20 16 30 17 31 14 30.07- 13 17 16 20 14 16 09.08- 31 17 58 15 39 15 19.08- 16 13 16 16 39 12 01.05-28.08 218“ 107h 253* 99b 205“ 110b a Total rainfall during period b Deviation of the termic period of growth from reference value (100%). vates with /V,O-his(trimethyl-silyl)trifluoro- acetamide (BSTFA) and analysis by gas chro- matography-mass spectrometry (GC-MS), using selected-ion monitoring (SIM). Results and discussion lAA production in bacteria Nine out of ten bacteria (88%) in cultivars Kus- taa, Kymppi and Hjan Pokko of the 1990 har- vest were previously shown to produce lAA (Tuomi et al. 1994, 1995). To estimate the phys- iological significance of the presence of lAA- producing bacteria, lAA production per bacteri- al cell in the liquid growth media of the cultured bacteria was weighed against the bacterial counts and the endogenous lAA concentration of bar- ley grains. On the basis of these calculations, we estimated the bacteria in steeped barley to be capable of lAA production in amounts of bio- logical significance (Tuomi et al. 1994, 1995). Bacterial counts in the 1991 and 1992 harvests further support this assumption, since the counts in all samples were higher than the lowest ones found in the 1990 harvests (Fig. 1). As a conse- quence, bacterial lAA production would fall within the limits estimated for the crop of 1990. To further clarify this point, the endogenous lAA concentration in dry kernels (cv. Kymppi, 1992 harvest) was analysed. The result, 123 ± 63 g/g fresh wt, corresponds well with the lAA concen- tration on which the 1990 estimates were based (195 + 99 g/g fresh wt). Counts of fungi, on the other hand, were too low in both 1991 and 1992 - as they were in 1990 (Tuomi et al. 1994, 1995) - for fungal lAA production to be a factor of significance. Total counts of fungi and bacteria In 1992, August was inclined to be a damp and relatively cold month (Table 1). Just before har- vesting then, at a very crucial time in the devel- opment of the grain microflora, conditions were wet, and the water taken up by the seeds could not evaporate. As expected, the highest bacteri- al and fungal counts in all cultivars were there- fore found in 1992 (Fig. 1), when the weather favoured the attachment and proliferation of these organisms. In 1990 and 1991 no clear dif- ferences were seen in the profiles of the total counts of fungi and bacteria. This, too, was to 410 AGRICULTURAL SCIENCE IN FINLAND Vol. 4: 407—418. be expected since there were no marked differ- ences in either average temperatures or rainfall between these years. In all, 59 uncharacterized bacterial isolates were extracted. Eighteen of these isolates were from the crop of 1990 (6 in cv. Kymppi, 7 in Kustaa and 5 in Hjan Pokko), 24 from that of 1991 (8 in cv. Kymppi, 6 in Kustaa and 10 in Hjan Pokko) and 17 from that of 1992 (6 in cvs. Kymppi and Kustaa and 5 in Hjan Pokko). As seen in Figure 1, cv. Kymppi was clearly richest and cv. Hjan Pokko poorest in both bacteria and fungi. The reasons for this are not clear, although one may be that cv. Hjan Pokko has, in terms of surface area, the largest kernels and consequently less surface of attachment per grain than culti- vars Kymppi and Kustaa. Viable counts of actinomycetes in all sam- ples were low in comparison with both bacterial and fungal counts (< 102 cfu/g fresh wt of grain). No attempt was made to characterize these spe- cies. Fungal spectra A confusing array offungi, 114 isolates of yeasts and moulds belonging to 48 different species, were extracted from the three cultivars in 1990- 92 (Table 2). The commonest classes are listed in Figure 2, which shows that most of these spe- cies were present in all three cultivars and some of them in all three harvests of the cultivars. Xerophilic storage fungi, namely Aspergil- lus and Penicillium spp., were in a minority in all samples (Fig. 2) even though the isolation meth- od whould have favoured the appearance of these sporulating species. The levels of both Aspergil- lus and Penicillium spp. appear to rise, howev- er, when barley is steeped (Douglas and Flanni- gan 1988, Haikara et al. 1977) and it is there- fore important to note that they were present in most of the samples (Fig. 2). As well as harmful mycotoxins, members of both Aspergillus and Penicillium genera are known to produce vari- ous plant hormones (Pegg 1984, Tuomi et al. 1994, 1995). Aspergillus spp. and Penicillium spp. also produce many spores that are dissemi- nated by air and can cause respiratory diseases in people and animals (Mathre 1982). Counts of these organisms in the grains would have to be higher than those reported here, however, before they would give any cause for concern. On the contrary, the relatively low counts of these harm- ful storage fungi indicate that the grains were of good vigour and well suited for malting. One likely reason for the relatively low percentage of storage fungi is that the samples were all tak- en within a year of harvesting, and the mycoflo- ra would still be dominated by field fungi (Briggs 1978, Burger and Laßerge 1985). The most conspicuous field fungi were spe- cies of Rhodotorula, Cryptococcus and Aureo- basidium (A. pullulans), all yeastlike organisms of widespread occurrence (Jay 1986), and spe- cies of Drechslera , Cladosporium and Mycelia sterilia (Figs 2-3). Drechslera spp. include spe- cies ofplant pathogenic interest (see below) and even though not normally cited as occurring in high numbers in barley (Briggs 1978, Douglas and Flannigan 1988, Flannigan 1974, Flannigan Fig. 1.Total annual viable counts (cfu/g fresh wt of grain) of fungi and bacteria in cvs. Kymppi, Kustaa and Hjan Pok- koin 1990-1992. 411 AGRICULTURAL SCIENCE IN FINLAND Tuomi, T. & Rosenqvist, H.: Fungi and bacteria in malting barley Table 2. Fungal species isolated from cvs. Kymppi, Kustaa and Hjan Pokko in harvests of 1990, 1991 and 1992. Strain Number of isolates cv. Kymppi cv. Kustaa cv. Hjan Pokko ’9O ’9l ’92 ’9O ’9l ’92 ’9O ’9l ’92 Acrodontium crateriforme (v. Beyma) de Hoog - - - - - - - 1 Altemaria altemata (Fr.:Fr.) Keissler 3-1 ___ - - 2 Altemaria infectoria Simmons 1 - - - - - 1-1 Aspergillus flavus Link:Fr. 1 2 - - - 1 - 1 Aureobasidium pullulans (de Bary) Amaud 1 2 - - 2 2 - I 2 Botrytis cinerea Pers.:Fr. - - - - - 1 Candida spp. 1 - - Chalara austiaca (Faut. & Lamb.) Nag Raj & Kendrick - 1 Cladosporium cladosporioides (Fres.) de Vries 1-1 - -1 - II Cladosporium herbarum (Pers.:Fr.) Link - - 1 Cryptococcus albidus (Saito) Skinner var. albidus - - 1 - - 1 1-1 Cryptococcus infirmo-miniatus (okuniki) Phaff & Fell - - - - - - - 1 Cryptococcus laurentii (Kufferath) Skinner - - 1 - - 1 Drechslera anam. ofPyrenophora graminea - 2 1 Drechslera cf. sorokiniana - - - I__ ___ Drechslera sorokiniana (Sacc) Subram & Jain - 1 - 2-3 - - 1 Drechslera teres (Sacc.) Shoemaker - 1 Epicoccum nigrum Link 1-1 - - - - - 2 Fusarium spp. 5 n.i n.i 1 n.i n.i - n.i n.i Heterobasidium annosum (Fr.:Fr.) Bref - - - - 1 Hypocrea pulvinata Fuckel, isol. from Piptoporus betulinus - - - - 1 Mycelia sterilia 42 - 221 - -2 Penicilliumaurantiogriseum ___ - - - __l Penicillium cf. commune I 1 - I - - Penicillium corylophilum Dierckx 11 Penicillium crysogenumThom - - - 2 I - - 1 Pichia anomala (Hansen) Kurtzman - - - - - - - 1 Rhodolorula glutinis (Fres) Harrison 1 - - - - I - 1 1 Rhodotorula mucilaginosa (Jorgensen) Harrison - - 1 - - - - 1 Septoria nodorum (Berk) Berk - - - 1-1 Sordariafimicola (Rob.) Ces. & De not. - - - - - - - I Sporobolomyces roseus Kluyver & van Niel. - 1 - II Trichoderma viride Pers:Fr. 1 Ucladium botrytis Preuss ___ ___ __l Unidentified spp. 2-2 - - 5 1 Williopsis californica (Lodder) Krasil’nikov - - - 1 "' not isolated and Healy 1983, Haikara et al. 1977), these fun- gi appear to be of special importance and spread in Finnish barleys (Mäkelä 1972). The other groups mentioned, A. pullulans and Cladospo- rium spp. in particular, are more frequent ac- quaintances among the mycoflora of healthy barley grain (Briggs 1978, Douglas and Flanni- gan 1988, Flannigan 1974,Flannigan and Healy 1983. Haikara et al. 1977). The Cladosporium spp, found were either isolates of C. cladospo- rioides Fres. de Vries or C. herbarum (Pers.iFr.) Link. C. herbarum (Pers.:Fr.) Link, which was 412 AGRICULTURAL SCIENCE IN FINLAND Vol. 4: 407-^lB. Fig. 2. Viable counts of the fourteen most prominent fungal groups in cvs. Kymppi, Kustaa and Hjan Pokko in 1990-1992, 413 AGRICULTURAL SCIENCE IN FINLAND 2 Tuomi, T. & Rosenqvist, H.: Fungi and bacteria in malting barley found only in cv. Kymppi of the 1992 harvest, is a saprophyte that frequently parasites weakened or damp grain but, much like C. cladosporio- ides Fres. de Vries, is relatively unimportant as a seedborne infectant (Flannigan and Healy 1983). Many of the fungal groups listed in Table 2 have previously been found in barley varieties grown in Finland. Haikara et al. (1977) isolated fungi from four Finnish barley varieties (not cv. Kymppi, Kustaa or Hjan Pokko), and among the seven most common fungal genera listed by them all but Cephalosporium are included in Figures 2 and 3. Clearly, however, most of the fungal groups listed in Figures 2 and 3 are not specific for Finnish barley, most having been cited as common fungi in malting barley by workers us- ing both directplating and spread plating in dif- ferent countries the world over (Briggs 1978, Douglas and Flannigan 1988, Flannigan 1974, Flannigan and Healy 1983, Haikara et al. 1977).Ylimäki (1970, 1981) has also investigat- ed the mycoflora of several Finnish barley vari- eties (not cv. Kymppi, Kustaa or Hjan Pokko), but even though his studies spanned several years and covered grain fresh from harvest as well as samples of stored grain, he does not mention many of the species listed in Table 2. He did, however, list even more species of various gen- era than are given in Table 2. The reason for this spread in the results is probably that these pre- vious studies utilized direct plating of intact ker- nels on solid media. Direct plating of fungi on agar or filter paper is an efficient way of isolat- ing filamentous fungi (moulds) from intact seeds but, in our experience, is less suitable for ex- tracting bacteria and yeast-like organisms, which tend to be overgrown and displaced by moulds. Hence, the number of yeasts that showed on our media was higher than would be expected from direct plating. Our results are altogether more compatible with those of, for instance, Flanni- gan (1974), who used spread plating as well as direct plating to investigate the fungal flora of Bulgarian barley. In all samples, contamination with Fusari- um spp. was too rare for them to appear on dilu- tion plates. Direct plating ofcorns from the 1990 crops gave a maximum of 10% of grains con- taminated with Fusaria (in cv. Kymppi) and a minimum of 0% (in cv. Hjan Pokko) (Tuomi et al. 1995). Fig. 3. Mean values of viable countsof the fourteen most prominent fungal groups in cvs. Kymppi, Kustaa and Hjan Pokko in 1990-1992, expressed as percentages of total cfus. 414 AGRICULTURAL SCIENCE IN FINLAND Vol. 4: 407^18. Incidence of plant pathogenic fungi All samples contained only smut-free, apparently healthy grain. No reports of outbreaks of major epidemics of economic importance that would concern the harvests of the three cultivars stud- ied here have come to our attention. Neverthe- less, some species of plant pathogenic impor- tance were found whose incidence is difficult to link to harvesting yields (Mustonen et al. 1994). Septoria nodorum (Berk) Berk was present in cv. Kustaa of the 1990 and 1992 harvests. S. nodorum, cited as moderately common on two- rowed barley in Finland (Mäkelä and Mäki 1980), causes darkening of stems and leaf spots as well as foot and root rot (Mäkelä and Parikka 1980). Seeds are a known source of primary in- oculum for this fungus and can harbour S. nodo- rum for up to three years. Other plant pathogenic species found include species of Drechslera, which occurred in all three cultivars and sometimes in more than one crop (Table 2, Fig. 2); they were, in fact, among the ten most abundant fungi found (Figs 2-3). The 1991 crop of cv. Kymppi contained Drechslera teres (Sacc) Subraim & Jain (an- amorph of Pyrenophora teres), the causal organ- ism of net blotch (Kiesling 1985). This fungus persists from one growing season to the next as seedborne mycelium or as pseudothecia in in- fested host residue. Seedborne mycelium prob- ably serves to introduce the pathogen into fields previously free of net blotch (Mathre 1982). In Finland, the fungus has been observed to cause leaf spot on barley, but is probably of minor eco- nomic significance (Mäkelä 1972). Drechslera sorokiniana (Sacc) Subram & Jain (synonym of Helminthosporium sativum and Bipolaris sorokiniana, anamorph of Cochliobo- lus sativus) was found in all three cultivars and all three harvests (Table 2, Fig. 2). This fungus is, together with Fusarium culmorum and F. graminearum, cited as a cause of root rot and seedling blight in barley (Mathre 1982). A com- mon fungus in Finnish barley seed, it may have economic significance, as yield losses of up to 11%, with a mean of 6.3%, have been reported in field experiments (Kurppa 1984, 1985b). Seedborne inoculum is the most severe form of primary inoculum and may result in dead or stunted seedlings (Kiesling 1985, Mathre 1982). The infection incidence ofFinnish barleys (cvs. Kymppi, Kustaa and Hjan Pokko not considered) and invasion of D. somkiniana to the internal cell layers ofkernels is known to vary consider- ably, and not all varieties are susceptible to pathogenesis (Kurppa 1985a). Since no notable losses have been reported (Mustonen et al. 1994), it is possible that none of these three cultivars is susceptible to D. sorokiniana. The causal organism of barley stripe, Drechslera graminea (Rab.) Shoem. (anamorph ofPyrenophora graminea), was isolated from the 1991 and 1992 crops of cv. Kymppi. This seed- borne disease has been common in Finland for a long time and continues to be so (Mäkelä 1972, Mäkelä and Mäki 1980). The primary source of inoculum of this disease, too, is mycelium in infected seed producing systematically infected plants (Teviotdale and Hall 1976). Infected plants produce few seeds, and those that are formed are shrivelled. Losses are therefore directly propor- tional to the percentage of infected plants in a field. A number of spring barleys have been re- ported as resistant to the disease, whereas most winter barleys are susceptible (Mathre 1982). Like all malting barleys cultivated in Finland, cv. Kymppi, from which isolates of P graminea were found, is a spring barley. Conclusion In addition to the action of the above plant path- ogenic fungi, fungi of the genera Penicillium, Aspergillus, Fusarium, and Alternaria are known to have deleterious effects on the quality ofFinn- ish barleys owing to the production of various toxins. For these species to be of significance, though, higher counts than those reported here (Fig. 2) are required (Hietaniemi and Kumpu- lainen 1993). In damp years, the infection of Finnish barleys with Fusarium species in par- ticular has caused problems in the processing of 415 AGRICULTURAL SCIENCE IN FINLAND Tuomi, T. & Rosenqvist, H.: Fungi and bacteria in malting barley the grain (Haikara 1983). The small percentage of grains contaminated withFusaria in our sam- ples does not, however, give cause for concern and, on the whole, all samples seem to have been drawn from barley that - at least in terms of fun- gal and bacterial counts - were well suited for malting. Depending on the amounts released, the role of the bacterial lAA reported here might be to inhibit or stimulate germination while also stim- ulating enzymatic activity (Doran and Briggs 1993, Kieninger 1983, Kieninger and Blohm 1983, Li and Rehmanji 1991, Yamada 1984). In malting trials, similar amounts of added lAA have been noted to enhance the effect of added GA3 (Kieninger 1983, Kieninger and Blohm 1983,Palmer 1971). 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Annales Agriculturae Fenniae 20: 74-88. 417 AGRICULTURAL SCIENCE IN FINLAND Tuomi, T & Rosenqvist, H.: Fungi and bacteria in malting barley SELOSTUS Vuosittaisia vaihteluja suomalaisten mallasohrien pieneliöstössä ja niiden vaikutus liotetun ohran indoli-3-etikkahappopitoisuuteen Tapani Tuomi ja Heikki Rosenqvist Teknillinen korkeakoulu Kolmen yleisimmän suomalaisen mallasohralajikkeen jyvien bakteeri-, mikrosieni- (hiiva ja home) ja sä- desienipopulaatioiden vuosittaisia vaihteluita tutkit- tiin vuosina 1990-1992. Työn aikana mallastukseen käytetyistä ohraeristä eristettiin yhteensä 114 karak- terisoitua mikrosieni-, 59 tunnistamatonta bakteeri ja 12 tunnistamatonta sädesieni-isolaattia. Kasvihormonin, indoli-3-etikkahapon, saantoa jyväperäisten mikrobien rikastetuissa puhdasviljel- missä verrattiin mikrobien biomassaan jyvissä ja jy- vien indoli-3-etikkahappopitoisuuteen. Todettiin, että ottaen vuosittaiset vaihtelut huomioon, bakteereilla on kyky tuottaa indoli-3-etikkahappoa biologisesti merkittävissä määrin. Kuten satokausien aikaisten keskilämpötilojen ja sadesummien perusteella saattoi odottaa, bakteeri-, hiiva- ja homemäärät olivat kaikissa lajikkeissa kor- keimmillaan vuonna 1992. Suurin osa eristetyistä hii- voista ja homeista lukeutuvat saprofyytteihin. Domi- noivia lajeja olivat pellolta peräisin olevat Rhodoto- rula, Cryptococcus, Aureobasidium, Drechslera, Cla- dosporium ja Mycelia sterilia. Varastosienet olivat täten vähemmistönä ja kaiken kaikkiaan vaikuttaisi, että kunkin kolmen lajikkeen kaikki kolme vuosiker- taa koostuivat mikrobiologisesti hyvälaatuisesta, hy- vin mallastukseen soveltuvasta viljasta. Kasvipato- geeneiksi luettavia mikrosienilajeja olivat Septoria nodorum (lehti-ja tähkälaikku) sekä Drechlera teres, D. sorokiniana ja D. graminea (aiheuttavat mm. juu- rimätää ja taimituhoa). Mikrobi-invaasioiden määrän havaittiin poikke- avan selvästi ja johdonmukaisesti lajikkeesta toiseen. 418 AGRICULTURAL SCIENCE IN FINLAND