461 Effect of powdery mildew (Erysiphe graminis f.sp. tritici) on spring wheat in Finland Oiva Nissinen The Hankkija Plant Breeding Institute, Hyrylä Received April 2, 1973 Abstract. In 1970 —72 the effect of powdery mildew on Finnish spring wheats with different field resistance was studied. For the mildew control 1 kg/ha Karathane WD (22.5 % Dinocap) was used. These investigations showed that mildew control increased grain yields in susceptible varieties by 2.4 to 6.6 %. The 1000-grain weight increased by 2.2 to 5.3 %, respectively. On the more field resistant spring wheats mildew control had no particular effect. Mildew control evened out the relative yield differences between the varieties. The paper includes notes on the occurrence of mildew in Finland while the need for resistance breeding is also discussed. Reports from various Scandinavian countries indicate that powdery mildew is considered a very important plant disease, which causes great yield losses in wheat and barley (Hermansen 1968, Johansen 1963, Leijerstam 1962, 1965, 1972b, Svensson 1971). In Finland the amouts of yield losses caused by mildew are not known. Mildew is, however, frequent in most wheat fields every year, and many varieties display a high percentage of infection (Nissi- nen 1969). In the present paper an attempt is made to clarify the effect of powdery mildew on spring wheats and to discuss the importance of mildew resistant varieties in Finnish conditions. Material and methods The tests were carried out at The Hankkija Plant Breeding Institute. The trial fields and the varieties used in the tests are presented in Table 1. The method used was split plots with 4—6 replicates. Each plot measured 8 sq.m. The plots were fertilized with 1000 kg/ha of compound fertilizer. Thus 150 kg N, 88 kg P and 126 kg K were applied per hectare. https://www.c-info.fi/en/info/?token=BuVfn9ckCzyQNgZc.Yw4Tw--LuJqQ_QYyr1oM2w.RhZu3Yt2_zGtwRfPrV8-LA8P9mGV8gHexXtmyvlFXeABDCH1zlhiB7de9oJitqKU45FBfMrVb-C4XEl3DqSZuc7eoT8hHNwIPwbMBicQFZzs-myaa1Iro884LbwdifKMkS-YBrZcQd4-fRHHGDED1wInETH-7Rrz7rx6 462 Table 1. Effect of mildew control (spraying with Karathane 1 kg/ha) on the yields of some spring wheats in 1970 1972 in Finland, Trial field T t t v ' t Mildew Grain yield Yield increase 1000-grain weight and year reamen ane -v % kg/ha Ratio Change kg/ha % g Change Increase (%) Unsprayed Ruso 9 2945 100 2760-3055 38.4 37.8-38.9 * Touko 9 2896 98 2740-3062 36.3 35.5-37.0 Tammisto (60°) » Veka 4 2658 90 2603-2731 33.7 32.5-34.9 1970 Sprayed Ruso 5 3017 100 2940-3180 +72 +2.4 40.1 38,2-41.8 +4.4 » Touko 5 3020 100 2755-3261 +124 +4.2 37.4 36.3-38.1 +3.0 » Veka 1 2661 88 2472-2830 +3 +O.l 33.7 33.1-34,2 +O.O Unsprayed Ruso 12 4728 100 3840-5270 46.7 45.7-47.7 » Hja a 376 13 4610 94 4040-5120 48.4 47.0-50.7 Tammisto (60°) » Hja a!45 5 4912 104 4560-5320 43.2 43.0-43.7 1971 Sprayed Ruso 7 4925 100 4150-5560 +2OO +4.2 48.3 47.1-49.2 +3.4 » Hja a 376 7 4742 96 4550-5120 +132 +2.8 51.0 50.3-52.1 +5.3 » Hjaa 145 1 4895 99 4060-5350 -17 -0.3 42.7 42.1-43.5 —l.l Unsprayed Ruso 25 3950 100 3187-5425 45.8 45.0-46.9 i) Hja a 376 30 3727 94 3325-4887 46.5 45.6-48.0 Nikkilä (61°) » Hja a 145 5 4300 109 3562-5875 42.3 41.7-43.0 1971 Sprayed Ruso 10 4212 100 3437-5100 + 262 + 6.6 47.6 46.8 - 48.5 + 3.9 * Hja a 376 12 3919 93 3287-4650 +192 +5.1 47.8 46.1-50.4 +2.8 » Hja a 145 3 4360 103 3212-5362 +6O +1.4 43.0 42.9-44.8 +1.6 Unsprayed Ruso 10 4700 100 4312-5150 40.8 40.5-41.0 * Hjaa 1416 10 4796 102 4500-5075 36.2 35.9-36,5 Anttila (60°) » Hja a 145 3 5158 109 5050-5275 36.7 36.0-37.1 1972 Sprayed Ruso 6 4881 100 4575-5225 +lBl +3.8 41.9 41.5-42.2 +2.6 » Hjaa 1416 5 4933 101 4500-5212 +137 +2.8 37.0 36.9-37.2 +2.2 »Hja a!45 1 5062 103 4500-5300 -96 —l.B 36.7 36.0-37.1 +1.6 F-values for grain yields in 1972 t-values for grain yields in 1972 Karathane spraying 2.073° Unsprayed Karathane spraying Variety 5.146* Ruso —Hja a 145 3.129*** 1.224° Variety—Karathane spraying I.olB° Ruso —Hjaa 1416 <1 <1 (USDs % 217 kg/ha) Hja a145-Hjaa 1416 2.449* <1 463 For mildew control, 1 kg/ha Karathane WD (22.5 % Dinocap) in 1000 liters of water was used (Crosier and Szkolnik 1956, Smiljakovic 1966). Spraying was repeated three times with two weeks intervals, as from the appearance of mildew pustules, on June 21—26. The incidence of mildew was estimated at the time when it reached its maximum. The persentage of the leaf area covered by mildew on the upper four leaves was calculated. Results Karathane spraying increased the grain yields of Ruso, Touko, Hja a 376 and Hja a 1416, changing 2.4 to 6.6 %. The 1000-grain weight increased by 2.2 to 5.3 %, respectively. The mean increases in grain yield and 1000-grain weight in the Ruso variety were 4.2 and 3.6 %. On more field resistant varieties, Veka and Hja a 145, the effect of mildew control was not particularly noticeable (Table 1). The relative yield differences between susceptible varieties were same in both treatments. On the other land, the field resistant line Hja a 145 yielded 4—9 % more than Ruso on unsprayed plots. However, Karathane spraying increased the grain yields of Ruso so that the ratio of Hja a 145 was not more than 99—103 (Table 1). Owing to drought, there were some difficult- ies in shooting, and that may explain the great differences in yields between the replications. The occurrence of mildew was not very intensive in these years, perhaps because of the rather late occurrence and drought whichretarded the vigorous growth of the wheat stands. Karthane was not able to keep the stands completely free from mildew. Discussion In most years, high incidence of mildew in spring wheat is due to abundant mildew pustules on winter wheats in spring and early summer. Winter wheat is the main source of mildew infection on spring wheat. In South Finland the first traces of mildew in spring wheats occur around mid-June and the heaviest contamination takes place from the end of June to the end of July. Usually the best crops are most severely attacked. In many cases, however, mildew exhibits greatest damages with crop yields that are below average (Pollhamer 1965). For instance, drought increases the injuriousness of mildew because the fungus increases the transpiration and adds to the need for water. Finnish varieties are susceptible to mildew and show in many years a relatively high level of infection (Nissinen 1969, Fig. 1). The marked yield increases in the susceptible variety Ruso achieved by mildew control agree with the assumption that mildew must even in Finland be considered one of the minimum factors influencing specific yielding capacity. According to Large and Doling (1962, 1963), yield losses in barley in British circumstances could be expressed as 2.5 (/M %, where M means per cent green leaf area covered by mildew on the upper four leaves at heading stage. The corresponding scheme for winter wheat is 2 j/M%- Although too much stress should not be 464 laid upon these figures, they have been found to agree to a fairly large extent with the estimate of total yield loss in spring wheat formed on the basis of official varietal trials e.g. under Swedish conditions (Leijerstam 1962, 1972 b). Thus, if the mildew percentage is 1 to 10, the theoretical yield losses are 2 to 8 % of the total yield. In Finnish conditions the figures must be lower owing to the late occurrence of the mildew infection and the fast development of crops. It is also worth noticing that mildew control evens out the yield diffe- rences between varieties with various mildew infections. There are, however, some difficulties in studying the real effects of mildew on the total yield in field conditions. Mildew mainly affects grain development decreasing the 1000-grain weight. This is likely to be a good basis for estimating losses caused by mildew in different years. In Table 1 the figures of 1000-grain weight conform quite credibly to those of grain yields. Fig. 1. shows the differences in the development of mildew infection on varieties due to various levels of field resistance. The results stress the importance of this kind of resistance. It is likely that in Finnish conditions the specific field resistance of different varieties is brought about quite clearly by the short growing season and the fast development of crops. From the plant breeder’s point of view, choosing field resistant lines is, however, no solution to breeding mildew resistant varieties. According to Fajersson and Lundin (1969), combining a gene for mildew resistance into the field resis- tance variety Ring increases the grain yield in the new variety Rang in many cases by 10—15%. One reason for mildew control not having any distinct effect on the more field resistant varieties Veka and Hja a 145 in trials in 1970 72 could have been the fact that mildew in those years was quite late and Fig. 1. Development of mildew infection in some spring wheats at Tammisto Experimental Farm in 1968 (Nissinen 1971). Veka, Kara II x Tammi Hja a145, Veka X (Kärn II x Kimmo) Hja a3OB, Ruso x (Kimmo x Aurore) 465 infection was relatively low. It must also be noticed that Karathane is not effective enough to control mildew (Svensson 1971). Table 2. Reaction of test varieties to powdery mildew (Erysiphe graminis f.sp.tritici) in 1971 1972 in Finland. Trial field Variety Tammisto Anttila Nikkilä Lieto 60°N 60°N 61°N 60°N Ulka 2-3 2-3 1 2 Hope 3-4 3-4 3 4 Chul 3-4 3 3 4 Axminster 3 3 4 3 3—4 Normandie 0 1 0 1 1 0 1 Salzmiinde 14/44 1 0— 1 0 0 Halle 13471 0-1 0-1 0-1 0 Weihenstephan Mj 0— 1 0— 1 0— 1 0— 1 C.I. 12633 0-1 0 0 0 Idaed 598 0-2 111 FAO 163 b 0-2 0-2 2 1-2 Kenya x Lemphi 50 13596 0 0 0 0 Amphidiploid 15 AD 4/14-2/6 0 0 0-1 0-1 Norin 29 0-2 2 0, immune, no sign of infection 1, very resistant, minute lesions 2, moderately resistant, small lesions with slight necrosis 3, moderately susceptible, lesions medium in size, no necrosis 4, very susceptible, great pustules without necrosis Test varieties with different combinations of genes for resistance are also used in order to follow the variation of aggressiveness of mildew (Table 2). The racial population in Finland has not been examined very extensively and probably it is not worth while here to study different races individually. It is more important for the breeder to note which of the test varieties are attacked by fungus in order that he can select proper resistant genes in preparing breed- ing programs. According to Leijerstam (1962, 1965, 1972 a, 1972 b) the racial population does not deviate greatly in the different Scandinavian countries. Up to now, breeding for the race-specific resistance has been generally preferred. Risk of a rapid break down of resistance by new races of fungus is a great disadvantage connected to that kind of resistance. New efforts have also been made to improve the level of field resistance and to utilize it with race- specific resistance, because a certain level of field resistance is the best guarantee in various growing conditions. As Fig. 1 shows, breeders in Finland also have an opportunity to select more field resistant lines from their material. Table 1 also indicates that field resistance can be a relatively important characteristic in Finnish conditions and shows a valuable basis for breeding mildew resistant spring wheat varieties. 466 REFERENCES Crosier, W. and Szkolnik, M. 1956. Sulfur, Karathane and Actidione for Control of Powdery Mildew of Wheat. PI. Dis. Reptr. 40: 337 339. Fajersson, F, and Lundin, P. 1969. Weibulls Rang, ny mjöldaggsresistent värvetesort med hög kvalitet. (Weibull’s Rang, a new mildew' resistant, high-quality spring wheat variety.) Agri Hort. Gen, 27:1 28. Hermansen, J. E. 1968. Studies on the spread and survival of cereal rust and mildew diseases in Denmark. Friesia. Nordisk mykologisk Tidskrift 8; 1 206. Johansen, H. B. 1963. Loss of yield in spring barley due to attacks of powdery mildew (Ery- siphe graminis DC). Kgl. Vet.- & Landbohojskole. Arssk. 1963: 54 63. Large, E. C. and Doling, D. A. 1962. The measurement of cereal mildew and its effect on yield. PI. Path. 11:47-57. * 1963. Effect of mildew on yield of winter wheat. PI, Path. 12: 128 130. Leijerstam, B. 1962. Studies in powdery mildew on wheat in Sweden. I. Physiological races in Scandinavia in 1960 1961. Stat. växtskyddsanst, 94: 279 293. » 1965. Studies in powdery mildew on wheat in Sweden. 11. Physiological races in Scan- dinavia in 1962 and 1963 and the resistance in a number of wheats to Scandinavian races. Stat. växtskyddsanst. 103:169—183. » 1972 a. Studies in powdery mildew on wheat in Sweden. IV. Inventory of sources of resistance to the Scandinavian race population complex. Stat. växtskyddsanst. 145: 249-270. » 1972 b. Race-Specific Resistance to Wheat Powdery Mildew. Stat. växtskyddsanst, 146; 273-277. Nissinen, O. 1969. Notes on the incidence of mildew (Erysiphe graminis f.sp.tritici) and leaf rust (Puccinia recondita) in spring wheat at Tammisto, summer 1968. Peat & Plant News 3: 38 40. * 1971. Härmänkestävyysjalostuksen merkityksestä syys- ja kevätvehnällä. Hankkijan Saroilta 3: 9. Pollhamer, E. 1965. The mildew-resistant summer barley variety MK 42. Acta Agr. Hung. Tomus 14: 65 77. Smiljakovic, H. 1966. Investigation of the Biology, Ecology and Control of Erysiphe graminis DC. on Wheat in Serbia. Inst, small Grains, Kragujevac 1: 5 76. Svensson, L. 1971. Försök med bekämpning av mjöldagg pä sträsäd. Växtskyddsnotiser 1: 17-20. 467 Selostus Viljahärmän merkitys kevätvehnällä Suomessa vuosina 1970—1972, Oiva Nissinen Hankkijan kasvin]alostuslaitos, Hyrylä Kemiallisen torjunnan avulla pyrittiin selvittämään viljahärmän vaikutusta kevätvehnän satoon. Kokeet järjestettiin Hankkijan kasvinjalostuslaitoksen koekentillä vuosina 1970 1972. Härmäntorjuntaan käytettiin 1 kg/ha Karathane WU-valrnistetta, jossa vaikuttavana aineena on dinokappi (22.5 %). Karathane-ruiskutus lisäsi härmänalttiiden jalosteiden. Ruso, Touko, Hja a376 ja Hja a!416 satoa, sadonlisäyksen vaihdellessa 2.4 —5.6 %. Vastaavasti lisäykset 1 000-jyvän pai- noissa vaihtelivat 2,2 —5.3 %. Keskimääräinen sadon ja 1 000-jyvän painon lisäys Ruso- kevätvehnällä oli 4.2 ja 3.6 %. Kenttäkestävillä jalosteilla, Vekalla ja Hja a!45;11ä härmän- torjunnalla ei saatu mainittavia sadonlisäyksiä. Härmänalttiilla lajikkeilla suhteelliset satoerot olivat samansuuruiset sekä ruiskuttamatto- milla että ruiskutetuilla koejäsenillä. Ilman härmäntorjuntaa Hja a!45 oli 4 9 % Rusoa sa- toisampi. Karathaneruiskutus kohotti kuitenkin Ruson jyväsatoja niin, että satoero Hja Hja a!4s:n hyväksi oli parhaimmillaan enää 3 %. Tulokset antavat aihetta olettaa, että myös meillä härmänkestävyys voi muodostua yh- deksi minimitekijäksi lajikkeen sadontuottokyvyn kannalta. Näin ollen härmänkestäyys on katsottava yhdeksi lajikeominaisuudeksi, johon tulevaisuuden vehnänjulostuksen tulee kiin- nittää huomiota.