455 JOURNAL OF THE SCIENTIFIC AGRICULTURAL SOCIETY OF FINLAND Maataloustieteellinen A ikakauskirja Vol. 50:455-467. 1978 Fungus diseases of field bean in Finland during 1975—1977 Anna-Liisa Ruokola and Mauritz Vestberg University of Helsinki, Department of Plant Pathology, SF-00710 Helsinki 71 Abstract. During 1975 1977, studies were carried out on the fungus diseases of field bean and attempts were made to find, through seed-dusting trials, suitable methods for their control. The fungal flora in a total of 43 seed lots containing 140 200 seeds each were determined. In addition, plant samples collected from farms where field beans were under cultivation and field bean cultivar trials in seven localities were anal- ysed. The weather conditions in the growing seasons of 1975 and 1977 were rather ex- ceptional, the former being dry and warm and the latter rainy and cool. Ripe crops were obtained from the control experiments, in which the seeds of 3—4 field bean cultivars were dusted with thiram and benomyl preparations, only in 1975 and 1976. Ascochyta fabae Speg. was rare in all the seed samples apart from those from Länsi- Hahkiala, where the degree of infection varied, depending on the cultivar, from 1.3 20 %. Botrytis fabae Sard, was rare in the seeds, B. cinerea Pers. ex Fr. quite common in 1976 and especially in 1977. The frequency of the Fusarium fungi were very great on the seeds in 1977, F. culmorum (W. G. Sm.) Sacc. and F. avenaceum (Fr.) Sacc. being the most common. A. fabae was quite common in the stand samples collected at Länsi-Hahkiala in 1975 and 1976. The chocolate spot-causing agents, B. fabae and B. cinerea, were rela- tively rare in all years except 1977, when some cultivars were heavily infested by B. cinerea. Introduction Cultivation of the field bean (Vida faha L.) has greatly increased in the Nordic countries since the last decade. Attention has thus been focused on the fungus diseases affecting the cultivation of this plant and on the possibilities of controlling them. Information about fungus diseases of V. faha is available from, for instance, China (Yu 1947), Argentina (Spegazzini 1899), the Soviet Union (Chekalins- kaya 1963), Iran (Kaiser et al. 1967), England (Hewett 1973) and Norway (Sundheim 1973). The most important pathogens of this plant have been found to be Ascochyta fabae Speg., Botrytis cinerea Pers. ex Fr. and B. fahae Sard, (all causing leaf lesions), the last mentioned one being more damaging than B. cinerea (Deverall and Wood 1961, Sundheim 1973). The cultivation of field bean in Finland is restricted by the length of the growing season. Almost all the foreign cultivars require too long a growing period to be grown under the conditions prevailing in Finland. Breeding work https://www.c-info.fi/en/info/?token=fAdmYFoBAG2rEeJB.ZRL7gxVnzRIgx-1_PbIcJw.oqADEKzHqQSmtl0aMMPndga4kHvPsZlniFy-QZ1d2Bw96d7cE5V3m4ciJjUjm5SE1_KFZf0P7EfRetLjS5sRW-MqsBnLwr-GTh-T9PGzjeXrDzMXXvqWktkEp3R8cGHXcJlN8N_PT1rVOV1FQDC0fnz70I_PoztVkdF6N3Vf8WywZGX0rkbW-0Oqf_vxr7tXA2wfAC8 456 using old native varieties from Southeast Finland was therefore started in 1969 at Hankki] a’s experimental station in Anttila (Hovinen and Kivi 1976). As a result, one improved cultivar is already on the market the early and small-seeded Mikko. The aim of this study is to determine the species of fungi causing diseases in stands and seeds of field bean under Finnish conditions and their practical importance. Material and methods During 1975—77 a seed-dusting experiment was carried out on the Viikki Experimental Farm. The field bean cultivers Mikko and the native variety Pirhonen were grown throughout the duration of the experiments, the Swedish varieties Sving and Primus in 1975 only, and Aria in 1976 and 1977. Dusting was carried out with benomyl and thiram preparations, in 1975 with the latter only. The dusting trial was combined in 1975 with a cultivar trial which included the cultivars Aria, the German Herz Freya and Hankkija lines 70006 and 70028. When the seeds were checked for healthiness the number of seeds in each lot was found to vary from 140 to 200. Untreated and surface sterilized seeds were used in 1975, but in subsequent years surface sterilized seeds were used almost exclusively. Seed treatment and incubation was carried out using the same methods as described earlier (Ruokola and Kössi 1977), with slight modifications. The seeds were soaked for 10 min. in NaCIO- (1 % clorine) solution to destroy saprophytic fungi. In addition to cellulose discs, the seeds were also incubated on weak CM- (12 g/I corn meal (Difco) + 300 ppm strep- tomycin/1) agar (WCMA) to induce growth of the pathogenic fungi. Plant samples were taken from 7 different localities (Fig. 1), most of them, however being from the experimental field of the Institute of Plant Pathology. Sampling took place during different growth stages. The microbes were isolated from infected parts of the plants using the method described earlier (Ruokola and Kössi 1977). CMA, PDA (Difco) and Czapec-Dox agar were used as the growth media. Most of the transfers were soaked for one hour in streptomycin solution (300 ppm 1) to inhibit bacteria. Weather conditions In 1975 the growing season at the southern sites, i.e. Viikki, Tikkurila and Tuusula, was on average very warm with only slight rainfall. The summer was cooler in Länsi-Hahkiala than at the other localities. Total precipitation here during the growing season was lower than normal. In 1976, the growing season, apart from in May, was cooler than normal. The monthly precipitation sums were also generally lower than normal. The rather heavy rain in Länsi-Hahkiala in July was exceptional. In 1977, the start of the growing season at Viikki and Tuusula was warmer than normal and less rain than normal fell in Viikki. The rather cool period which started in the middle of the summer continued up until October and precipitation, especially in July, was heavy. 457 Results Seed-dusting trials A combined seed-dusting and cultivar experiment was set up in Viikki in 1975. A total of eight field bean cultivars were used, four in the dusting ex- periment and four in the cultivar experiment. Owing to the severe dry period which occurred during the growing season, the early cultivar, Mikko, was harvested already at the beginning of August and the rest during August. Of these, Primus was the latest, its growing period lasting for 103 days. Seed yields were overall rather low, varying from 1 128 to 1 977 kg/ha, which is rather a lot less than the normal yield of 3 000 kg/ha. There were no significant differences between the yields, weight of 1 000 seeds, volume weight and plant density of the dusted and correspond- ing undusted test units. The growing season in 1976 was favourable for the development of Vida faba and hence the seed yields of two of the cultivars used in the dusting ex- periment, Mikko and Pirhonen, were rather good. The seed yields for Mikko ranged from 4 722 to 5 026 kg/ha and for Pirhonen from 4 085 to 4 511 kg/ha. However, no reliable differences as regards yields were found between different treatments. No crop was obtained from Aria owing to the poor germination of the seeds. The weather conditions prevailing at Viikki in 1977 were unfavourable for the development of field bean since ripened seeds were not obtained from any of the cultivars used in the experiment. Identifications of the fungi Seeds Altogether a total of 43 seed lots comprising 5 040 seeds were analysed. A total of 3 315 fungus determinations were carried out on these seeds, either the species or at least the genus to which the fungi belonged being determined (Table 1). The fungal species and the frequency of occurrence of certain species of fungi varied considerably depending upon site type, cultivar and experimental year. In the analyses carried out in 1975, the most diverse microflora were found in the seed lots representing the yields obtained in Länsi-Hahkiala and Viikki (Table 2). The most pathogenic fungi, especially A. fabae, were found in the samples from Länsi-Hahkiala. It was most common in the native variety Pirhonen. Hardly any A. fabae or B. fabae fungi were found in the sample lots from Viikki in 1976 and 1977 (Table 3). On the other hand, B. cinerea and Fusarium fungi were exceptionally common in the seed lots in 1977. The Fusarium fungi determined from all the seeds were, in order of frequency, as follows; F. culmorum (W. G. Sm.) Sacc., F. avenaceum (Fr.) Sacc., F. sambucinum Fuckel, F. poae (Peck) Wollenw., F. semitectum Berk, et Rav., and F. gram- inearum Schw. 458 Table 1. Determined fungi, no. of infected seeds and their percentage out of all seeds investigated. Fungus No. % Absidia sp 1 0.02 Acremoniella atra Corda 19 0.4 Alternaria alternata (Fr.) Keissl 120 2.4 Arthrinium phaeospermum Fuck 5 0.1 Ascochyta fabae Speg 98 1.9 Aspergillus spp 31 0.6 Aureobasidium pullulans (de Bary) Arnaud 76 1,5 Botrytis cinerea Pers. ex Fr 177 3.5 B. fabae Sard 6 0.1 Cephalosporium spp 6 0.1 Chaetomium spp 5 0.1 Chrysosporium pannorum Link 93 1.8 Cladosporium spp 947 18.8 Epicoccum nigrum Link 1 0.02 Fusarium spp 188 3.7 Fusidium sp 1 0.02 Gliocladium spp 4 0.1 Mucor spp 290 5.8 Ostracoderma state of Peziza ostracoderma Korf 1 0.02 Paecilomyces sp 1 0.02 Penicillium spp 583 11,6 Phoma spp 133 2.6 Rhizoctonia sp 1 0.02 Rhizopus nigricans Ehrenb 433 8.6 Scopulariopsis brevicaulis (Bain.) Thom 1 0.02 Sordaria fimicola (Roberge) Ces. & de Not 1 0,02 Trichoderma viride Pers. ex Fr 57 1.1 Trichothecium roseum Link 2 0.04 Ulocladium consortiale (Thiim.) Simm 33 0.7 Verticillium tenerum (Nees ex Pers.) Link 1 0.02 Total 3 315 In 1977, the Phoma species, P. herbarum Westend and P. eupyrena Sacc., were also isolated from very many samples, in one lot of Mikko seeds about 40 % of the seeds were infected with P. eupyrena. When seed lots with germination percentages of less than 20 were excluded, the germination percentage of the seeds varied from 25 to 100. In 1975, germ- ination clearly decreased as the proportion of seeds in the seed lots from different cultivars which were infected with fungi or bacteria increased, r = 0.718*. In 1976, the correlation between germination percentage and the number of bacteria and fungi isolated from the different cultivars was similar to that found the previous year, r = —0.712*. The seed lots, apart from Mikko ones, were 100 % infected in 1977. Plant samples Altogether 39 different species of fungi were isolated from the field bean stands, but part of them were classified only at the genus level. The number 459 Table 2. Germination of Vida faba seeds and microflora isolated from yield during years 1973-1975. Number of seeds per sample: 1973 1974 40, 1975 120; WCMA medium; untreated seeds and seeds treated with NaCIO and streptomycin, Results combined. Microorganisms d. % § 8 8* O. S Oh O* - "S n s w Site, year g 5* » & »> S —"S 73O .s 0) ~ n. ~ +J rt « 13and cultivar +3 g « v> s -2 1 .c +e o •S g> £ S 1118. § a K 3 g -gE 2 b c o r ~ o o «o ovi w öf) o £ 2 ® S § aI ’g § ‘8 •» SIS’ ? g> tJ 4) d O S o 10 c SO Oh m Bqh,OmTsO§ n, ft; 555 5 (n w Anttila 1973 Primus 43 12 18 1 12 43 9 Mikko 95 2 6 8 Herz Freya 80 2 9 4 15 Hja 70028 95 2 3 6 11 Sving 100 1 4 4 9 Aria 83 111 3 Hja 70006 88 1 2 1 Pirhonen 1974 ... 60 21 2 1 13 37 2 Viikki 1975 Primus 51 1 2 2 13 20 71 3 9 121 4 Mikko 95 2 6 22 2 32 1 Pirhonen 83 1 2 64 3 70 1 Herz Freya 46 1 11 11 2 15 60 3 16 119 10 Hja 70028 87 4 1 2 26 3 36 1 Sving 59 11 10 15 80 5 9 130 6 Aria 77 1 2 3 2 44 2 2 56 Hja 70006 91 6 11 23 9 49 2 Länsi-Hahkiala 1975 Primus 85 4 6 2 1 1 11 5 16 11 7 64 1 Mikko 67 42 1 5 24 2 22 16 17 129 Pirhonen 64 50 5 2 4 23 2 23 53 162 2 of isolates of the most important fungi was 130 (Table 4). In 1975, leaf sample transfers were taken in the proportion of 2.5: 1 to other types of sample (stem, root and pod); in other years the proportion was 3: 2. AUernaria alternata, which is considered to be a saprophyte, was frequently found together with pathogens causing spot diseases. Sometimes, however, it also' grew as the only fungus transferred from stems or leaf spots. In 1977, when the weather conditions prevailing during the growing season were rather unfavourable for the ripening of field bean, the condition of the plants in the dusting experiment was estimated at the end of August using the scale 0—5. 0 indicated a healthy plant and 5 a completely infected plant. The following mean values were obtained; Arla Mikko Pirhonen 3.451.951.50 1,95 Cultivars F 7.21* LSD, 1.18 *0.06 460 Table 3. Frequency of occurrence of microorganisms in seed crop of dusting experiments at Viikki 1976-1977. Samples: 100 seeds/test unit, 400/cultivar; WCMA medium, treated with NaCIO and strepto- mycin. d o/ a 9* d/o « o, S 9< ö « o. :s 2 . 0 S m Z S d, s d *.73 1 -SYe*r and % gi®S | s, I§iMS-J g g| ig I dcultivar c m £-2 | | * S « |g. . g ‘g E I i£ * I 111 si| | |-s I .S-c Hi ~ 01 ta 8 o • s §5“~« s s ~ 5 S .Jy 72 B o s 3 O ft, § ft, n, 05 sd .S ft) ft, m 1976 Mikko 92 12 5 18 6 59 1 7 5 12 125 25 Pirhonen 75 1 16 2 12 12 21 72 8 13 4 10 4 175 83 1977 Arla - 40 72 4 236 98 11 18 4 3 5 491 400 Mikko 32 65 46 21 43 167 39 10 89 1 23 8 512 379 Pirhonen 30 32 4 2 177 79 3 16 4 3 5 355 400 Table 4. Most important fungi isolated from field bean stands in 1975 1977. No. of isolates Cfl 2 5“ a.iQ » tr1 Q Cl,'S, S Q, « O.*s& g ” .2 « I 8 I £ -a. I' g s «o o . O S O5 05 05 ft, ft, o, 5 rt