Grain yield, net blotch and scald of barley in Finnish official variety trials Jonathan Robinson AgriculturalResearch Centre ofFinland , Institute ofCrop and Soil Science. Plant Breeding Section, FIN-31600 Jokioinen, Finland, e-mail: jonathan.robinson@mtt.fi Marja Jalli Agricultural Research Centre ofFinland. Institute of Crop Protection, Plant Pathology Section, FIN-31600 Jokioinen, Finland Data on grain yield, and terminal severity of net blotch (Pyrenophora teres f teres) and scald (Rhyn- chosporium secalis) from Finnish official barley (Hordeum vulgare) variety trials were analysed to indicate the pattern of disease incidence over six years and five sites for nineteen barley genotypes, and the effect of the diseases on yield and the genotype by environment interaction for yield. The effect of climatic factors on net blotch severity were also investigated. The genotype by site interac- tion for net blotch severity was not statistically significant, but that for yield was. Net blotch severity differed between years, but was similar across sites and there were statistically significant first order interactions between year, site and genotype. ‘Saana’ and ‘Thule’ had relatively low mean terminal net blotch scores and their reaction to the disease was less sensitive to the environment than was that of ‘Tyra’ for example. Analysis of yield data adjusted for net blotch severity indicated that the mag- nitude of the genotype by environment interaction terms were not accounted for to any significant degree by differences in relative net blotch resistances among the barley genotypes. Overall, mean scores for scald severity were lower than those for net blotch. Terminal net blotch severity was corre- lated with May rainfall and growing degree days. Key words: Foliar diseases, genotype by environment interaction Hordeum vulgare, Pyrenophora teres, Rhynchosporium secalis Introduction Net blotch, caused by the fungus Pyrenophora teres Drechs./ teres Smedeg., and scald, caused by the fungus Rhynchosporium secalis (Oud.) J.J. Davis, are the two principal pathogens of bar- ley, Hordeum vulgare L., in Finland (Mäkelä 1974,Mäkelä 1975). Both diseases have a world- wide distribution and importance, and deploy- ment of barley cultivars resistant to these dis- eases has been a priority in many barley breed- © Agricultural and Food Science in Finland Manuscript received August 1997 399 Vol. 6(1997): 399-JOB. AGRICULTURAL AND FOOD SCIENCE IN FINLAND https://www.c-info.fi/en/info/?token=8bLo6GUj1pHzAPHS.Dmv-y-exkGXiDkCidrmFfg.DeZ6TJnikzEI8lWL9WUr8eDySUs15NkHQZPFya_iPmiFfxZ3PNPx7OPMSQGPnpJNRstip-4IGm8MD0HBkM6Ix2S-5un4L5wYEhIogUPb-BujI_ikhrSFNnxQZ7z0n6tRzR47ER5fmdCHETMnAy0632zgAVtMs9RTc7vqHEUx_E774e4fHXnPZhp0wX_xvKyhZGRnoN1sZ9RULTXwrIjbkSwa8fYMNMUzBxYRHmLK9CJTihazLt4XIFihVhD3Ebf8SpwkqS-C5LcUYpVZD9-AJ1NGbO_U Robinson, J. & Jalli, M. Grainyield, net blotch and scald ofbarley ing programmes (Shipton et al. 1973, Shipton et al. 1974, Vivar et al. 1987). Robinson and Jalli (1996) and Robinson et al. (1996) indicated that in Finland, under artificially induced epidemics of net blotch and scald, there were small reduc- tions in grain yield and reductions in quality characteristics of the grain. Little is known about the effects of naturally occurring epidemics of the diseases on barley grain yield in Finland. Scald is reported to cause very severe yield loss in Norway (Ringlund and Bjprnstad, pers. comm.) and natural epidemics of net blotch can cause up to 40% yield loss (Mathre 1982). In Finland data have been compiled on the disease reaction and grain yield of many barley genotypes grown in a range of environments (sites and years). Using data from official varie- ty trials, the objectives of the investigations re- ported here were to establish the nature of the infection pattern for net blotch and scald over various environments for a range of spring bar- leys, including both six and two-row genotypes. In conjunction with data for yield recorded from the same trials, an attempt was made to estab- lish ifthe genotype by environment interactions for yield could be accounted for in terms of the differential effects of disease resistances among the barley genotypes included in the study. Bak- er (1971) demonstrated that stem rust, Puccinia graminis Pers. f. sp. tritici, and leaf rust, Puc- cinia recondita Rob. Ex. Des., infection of wheat, Triticum aestivum L., in Canada were important considerations in estimating the genotype by environment interaction for yield. Nissilä (1996) indicated that disease resistance of barley in Fin- land had an apparent influence on the relation- ship between the phenotype and genotype by environment interactions for yield under stress conditions. Early summer droughts frequently reduce barley yields in southern Finland (Mukula 1988, Mukula and Rantanen 1989), but the climatic conditions promoting disease development in barley have not been investigated. An additional aim of the work reported here was to establish the effect of rainfall and growing degree days (GDD) on terminal net blotch severity. Material and methods Data on mean grain yields and mean net blotch and scald severities were analysed for 19 Nordic spring barley genotypes grown in replicated (2-4 replicate blocks) official variety trials at five sites over six years (1991 to 1996).All trials were sown in May and fungicide seed dressing was discon- tinued beyond 1991. One site-year combination was missing (sat 1996) and datasets were not com- pletely balanced. The sites included, sat (61°16’N), epo (62°56’N), esa (61°44’N), hja (60°25’N) and lou (60°38’N). The barley materi- al included the six-row genotypes, ‘Arra’, ‘Art- tu’, ‘Arve’, ‘Botnia’, Hja 87061, Jo 1632, ‘Lovi- isa’, ‘Pohto’, ‘Pokko’, and ‘Thule’, and the two- row genotypes, ‘Filippa’, ‘lnari’, ‘Kinnan’, ‘Kus- taa’, ‘Kymppi’, ‘Mette’, ‘Saana’, ‘Tyra’ and ‘Vi- ivi’. The foliar disease severities, arising from natural epidemics, were assessed at around GS 60 (Tottman and Makepeace 1979) for entire plots according to Saari and Prescott (1975) on a scale from zero to ten, where zero indicates no infec- tion, and ten indicates extreme susceptibility, with severe infection on all leaves. Climatic data, dai- ly rainfall and GDD >O°C (Saarikko and Carter 1996), were taken from the central database at the Agricultural Research Centre ofFinland. Analyses of variance of grain yield and net blotch data were done on means over replicates using PROC GLM (SAS Institute 1989). Covar- iance analysis of yield data adjusted for termi- nal net blotch severity was done using the same procedure. The second order interaction, geno- type by site by year, was used as the error term for gauging the genotype main effect and inter- action terms. The year by site interaction was used as the error term in assessing the signifi- cance of the site and year main effects. Stability (sensitivity) analyses for the net blotch data were doneaccording to Finlay and Wilkinson (1963), following establishment of statistical signifi- cance of interaction terms, with mean net blotch scores plotted against environmental means, and regression coefficients plotted against genotype means across environments. 400 AGRICULTURAL AND FOOD SCIENCE IN FINLAND Regression analyses for climatic data and net blotch terminal severities, and homogeneity of slopes and intercepts, were determined using PROC REG (SAS Institute 1989) and PROC GLM (Littell et al. 1991). Components of vari- ance were determined with PROC VARCOMP (SAS Institute 1989). Results The plot of mean barley grain yields from the five sites over six years reveals considerable dif- ferences in yields associated with site and year (Fig. 1). There is, however, a discernible gener- al pattern of yields at the five sites; a drop in yield between 1991 and 1992, with a subsequent increase in 1993, followed by a slight fall in 1994. A similar plot for terminal net blotch in- fection (Fig. 2) indicates a pattern virtually con- sistent at sites over years, with a drop in infec- tion from 1991 to 1992, followed by a levelling off and a subsequent steady rise in infection lev- els up to 1996. There is no immediateevidence, however, of a simple relationship between net blotch and yield from comparison of Figures 1 and 2. The plot for scald incidence (Fig. 3) is very different to that for net blotch. The disease was only evident at two sites (lou and epo), and varied greatly in incidence and severity among years at those sites. Again, there is no obvious relationship between scald incidence and yield, nor between scald and net blotch incidence. The results of analyses of variance of yield and net blotch data are given in Table 1; analy- sis of data for scald incidence were omitted be- cause of low diseases incidence at most loca- tions. It is apparent that for yield, all first order interactions between genotype, site and year are highly significant, the year by site interaction having the largest mean square. The main effect of site was not statistically significant and the annual variation was only significant at P<0.05. For net blotch, the site effect was again not sta- tistically significant, but interaction terms, with Fig. 1.Meanbarley grain yields from 19 spring barley gen- otypes grown in Finnish official variety trials conducted at five sites over six years. Fig. 2. Mean terminal net blotch severity scores from 19 spring barley genotypes grown in Finnish official variety trials conducted at five sites over six years. Fig. 3. Mean terminal scald severity scores from 19 spring barley genotypes grown in Finnish official barley variety trials conducted at five sites over six years. 401 Vol. 6 (1997): 399^08. AGRICULTURAL AND FOOD SCIENCE IN FINLAND Robinson, J. & Jalli, M. Grain yield, net blotch and scald ofbarley Table 1.Analyses of variance (degrees of freedom, mean squares and variance ratios) for grain yield and terminal net blotch severity data from 19barley genotypes grown in Finnish official variety trials conduct- ed at five sites over six years, and of yield data with net blotch data used as a covariate. Yield Net blotch Yield adjusted for net blotch Source df MS F df MS F df MS F site (s) 4 17.96 2.62ns 4 34.86 2.98ns 4 14.39 2.18ns year(y) 5 21.75 3.17* 5 362.67 31.03*** 5 13.32 2.02ns y*s 19 6.86 64.89*** 19 11.69 15.18*** 19 6.59 64.99*** genotype (g) 18 1.26 11.92*** 18 14.05 18.24*** 18 1.24 12.25*** g*y 85 0.28 2.6o*** 83 1.50 I.9s*** 83 0.26 2.56*** g*s 72 0.35 3.3l*** 72 0.61 0.79ns 72 0.34 3.3l*** error 258 0.11 253 0.77 247 0.10 n 462 455 450 ns, not statistically significant, P > 0.05; *, **, ***, statistically significant at P < 0.05, P < 0.01 and P< 0.001 respectively. the exception of that for genotype by site, were statistically significant. Analysis of the yield data adjusted for net blotch indicates that neither site nor year terms were statistically significant, but that the remaining terms all reached significance at P0.20). May ODD regressed on mean terminal net blotch severity was statistically significant (df = 1, 21; F = 27.03; P<0.001) and negative (y = - 16.18 x + 358.5). The data are not presented, but there was again indication of crossover interac- tions for the regressions for individual geno- types, and the line for ‘Arve’ was distinct from the rest. The coefficient of determination (r2 = 0.56) for the mean regression was smaller than that for the mean regression of May rainfall on net blotch severity (r2 = 0.77). Regression for Fig. 5. Regression coefficients plotted against mean termi- nal net blotch severity scores for 19 spring barley geno- types grown in Finnish official variety trials conducted at five sites over six years. Solid circles represent 2-row bar- leys and open circles 6-row barleys. Fig. 6. Regression plots of May rainfall on terminal net blotch severity scores for 19 spring barley genotypes grown in Finnish official variety trials conducted at five sites over six years. The mean regression is represented by the bro- ken line and the equation governing it, and the coefficient of determination are given. 403 Vol. 6 (1997): 399^108. AGRICULTURAL AND FOOD SCIENCE IN FINLAND Robinson, J. & Jalli, M. Grain yield, net blotch and scald of barley the dataset including ‘Arra’, ‘Arve’ and ‘Pohto’, confirmed these results (Fig. 8). There was, how- ever, no statistically significant difference in in- tercept or slopes for the three individual lines (P>0.10). As for the May rainfall, GDD data re- gressed on net blotch severity fit linear models. It was indicated that multiple regressions, incorporating both May rainfall and GDD, pro- vided slightly better fits than simple regressions, but given that the two factors were significantly correlated (n = 53; r = -0.51; PcO.OO 1), a bivar- iate analysis provided no greater insight into the effects than univariate ones. Planting date of the trials did not have a sta- tistically significantly effect on terminal net blotch severity (P>0.05), and there were no sta- tistically significant ties between either rainfall or GDD on terminal net blotch severity for months other than May. Neither May rainfall nor May GDD were correlated with final grain yields (P>0.05). Discussion The principal purpose of the Finnish official bar- ley variety trials is to assess the value of new genotypes and make recommendations to grow- ers, and breeders, on yield and quality parame- ters. Nissilä (1996) analysed datasets of barley yield from official variety trials conducted in Finland between 1970 and 1989, with a view to establishing the significance of genotype by en- vironment interaction and the consequences of it for barley breeding - whether to breed for wide or narrow adaptation. He attempted to establish the determinants of crossover interaction for yield among a range of barley genotypes by ac- counting for the differential effect of biotic and abiotic stresses on barley growth and yield. Fac- tors including soil pH, rainfall during the grow- ing period and temperature patterns were found to be important. Disease resistance was also not- ed to influence the relationship between pheno- type and genotype by environment interaction. The results of the analyses reported here are not in disagreement with the possibility that disease- induced stress is a determinant of yield capacity in barley, but the relationship between disease severity, in this instance net blotch and scald, and expressed as foliar symptoms, using a sim- ple scoring procedure, and yield is not immedi- ately obvious. Fig. 7. Regression plots of May rainfall on terminal net blotch severity scores for three 6-row spring barley geno- types grown in Finnish official variety trials conducted in 53 environments. The equations for each regression and the coefficients of determination are given. Fig. 8, Regression plots of May growing degree days(GDD) on terminal netblotch severity scores for three 6-row spring barley genotypes grown in Finnish official variety trials con- ducted in 53 environments. The equations for each regres- sion and the coefficients of determination are given. 404 AGRICULTURAL AND FOOD SCIENCE IN FINLAND Nissilä (1992) established a highly signifi- cant difference for barley grain yields between years, but no interaction between genotypes and years, and commented that a series of three years (and six genotypes) might not have been suffi- cient to determine its importance. For these data (Table 1) this interaction was important. Baker (1971) in a study of the effect of leaf and stem rust of wheat on yields in Canada indicated the statistical non-significance of the genotype by year interaction term. Nissilä (1992) moreover, proposed that the genotype by site interaction was more important than genotype by year in- teraction in barley breeding for Finnish condi- tions. It is statistically significant in this study also. Scald, although considered an important dis- ease of barley in Finland, was not as severe as net blotch in the variety trials (Fig. 3). Any breed- ing strategy for scald resistance, if the disease were serious enough to affect the economic yield of barley, would have to be done at sites where the disease is important. Robinson et al. (1996) reported that there were differences in quantita- tive resistance among six Nordic six-row spring barleys, when artificially inoculated in the field with scald. However, these data indicate that natural scald epidemics in the 29 environments studied were seldom severe enough to differen- tiate the genotypes sufficiently well to provide useful information to barley breeders and grow- ers. Net blotch appears to be the more prevalent of the two foliar diseases of barley and the data contained in Figure 2 indicate that it occurred at all the five sites studied and that the pattern of net blotch infection was similar at the five sites withinany one year. This is interesting given the distance between the sites, and leads to specula- tion that some macro-climatic factor(s) deter- mine its severity. For scald there are very defi- nitely disease-prone environments, but for net blotch this appears not to be so, given the limi- tations of the sample dataset. This situation is likely to be a result of net blotch being compar- atively less demanding of environmental condi- tions (mostly wind dispersed) than scald (most- ly splash dispersed) for effective spore disper- sal and epidemic development. One of the purposes of looking at this data- set was to determine if a relationship between disease severity and yield could be determined. For net blotch, there was not a significant re- gression of mean disease severity against mean yield for each of the 29 environments (year by site combinations) for specific genotypes, nor overall. However, when the dataset was expand- ed to include 59 environments, although unbal- anced (data not shown), the linearregression was significant (df = I, 56; F = 4.90: P = 0.03), al- though the r 2 value was only 0.06. The nature of the relationship indicated however, that net blotch was more severe at higher yield levels. According to Baker (1990), disease incidence is assumed to be greater under environmental con- ditions conducive to higher yield. This appears to be the case for these data. It might therefore be more beneficial for growers and breeders alike to have yield data from disease-free plots so as to be able to estimate any yield loss associated with natural epidemics of barley diseases. Ro- binson and Jalli (1996) indicated that ‘Arve’ was particularly susceptible to net blotch under con- ditions of artificial inoculation in the field. H6221 (from which ‘Thule’ was derived) was noted to be resistant, and ‘Arttu’ and ‘Pohto’ were intermediate. This pattern appears to be reflected in the data contained in Figure 5 for infection under natural conditions. Baker (1971) determined that the occurrence of two of the major diseases of wheat, stem and leaf rust, had a significant influence on the gen- otype by environment interaction component for wheat yield, and that this was due to differences in disease resistance among the wheat genotypes under study. There is no evidence from these results to suggest that something similar occurs for barley and its two major foliar pathogens in Finnish official variety trials. Whereas Baker (1971) determined that the component of vari- ance for the genotype by site term was reduced considerably from an unadjusted to an adjusted value, this was not the case here and none of the genotype by site component of variance can be 405 Voi 6 (1997): 399-408. AGRICULTURAL AND FOOD SCIENCE IN FINLAND Robinson, J. & Jalli, M. Grainyield, net blotch and scald ofbarley attributed to variation in net blotch resistance among the barley genotypes. The data given in Table 1 indicate that analysis of mean grain yields adjusted for terminal net blotch severity had little effect on the mean squares and vari- ance ratios over those calculated for unadjusted values. The error mean square was reduced from 0.11 to 0.10 and therefore the power of the test was not increased using a covariate as little of the error was due to variation in net blotch. Com- ponents of variance for genotype by year and genotype by site terms accounted for 4.1% and 6.0%, and 3.1% and 5.4% of the total variance for unadjusted and adjusted data respectively. The data indicate that differences in resist- ance to net blotch appear to exist among the 19 barley genotypes included in this study. Howev- er, as they cannot be linked directly with yield, and yield loss, they are not of immediately ap- parent value. For example, ‘Arve’ appears to be tolerant of net blotch; symptom expression is consistently higher on ‘Arve’ across all environ- ments studied, than for any other genotype, and yet its yielding capacity was not diminished in comparison with that of the other barley geno- types. Symptom expression is misleading in this instance, although if the tolerance is real, it is potentially valuable to barley breeders. Dyke et al. (1995) considered that regression diagrams might occasionally be useful in revealing indi- vidual genotypes having special forms ofdisease susceptibility or resistance. ‘Arve’, with its symptomatic susceptibility to net blotch, appears to represent one such instance. May rainfall and GDD influence the extent of terminal net blotch severity. All trials were sown in May, although sowing date as such was not correlated with terminal net blotch severity. Rainfall and temperature are naturally correlat- ed and it can be surmised that sowing barley seed in a cool wet seedbed without a fungicide dress- ing increases the susceptibility of seedlings to infection from net blotch spores, possibly re- leased from infected stubble remaining from the previous season. An additionalpossibility is that such conditionsalso allow seed-borne infection to develop to maximum effect. This, however, according to these data is a less probable expla- nation as seed dressing was discontinued beyond 1991, and reference to Figure 2 indicates that terminal net blotch severity in 1991 was high. There remains the possibility however that cool, wet conditions decrease the efficacy of seed dressings: the seed dressing may simply be washed off during heavy rainfall preceding emer- gence. Useful work which might be done in the fu- ture with these datasets, and similar datasets, is to establish the extent and significance ofcross- over interaction for disease sensitivity, and de- termine the underlying reasons for it in terms of climatic and edaphic factors. In this way it might be established whether crossover interaction can be predicted, and therefore constitute useful in- formation to barley breeders and growers. It may be necessary to modify the method of assessing disease severity in order to be better able to make an association withyield loss resulting from dis- ease incidence. One shortcoming of the disease severity data is that they are collected solely at the end of the growing season and consequently it is impossible to comment on the timing of dis- ease appearance and its progress through the season. If disease build-up occurs early in the season it is more likely to affect yield negative- ly than if it occurs late. An additional possibili- ty is that some replicate blocks in the trials could be kept free ofdisease to allow comparison with yield under conditions of no disease. Disease severity could moreover be measured on sam- ples of individual leaves throughout the grow- ing season to allow identification of barley geno- types on which netblotch build-up is comparatively slow (James et al. 1968, Khan and D’Antuono 1985, Khan 1987). Acknowledgements. These data were collected and com- piled by a large number of staff from the Agricultural Re- search Centre of Finland. A. Kedonperä scored many of the trials for disease severity. S. Hyvärinen supplied the meteorological data. A, Järvi co-ordinated the trials and L. Mäkelä supplied the mean grain yield data with the assist- ance of I. Mattila. R. Aikasaloand E. Nissilä ofBoreal Plant Breeding made useful comments on the work and T. Tur- peinen is thanked for helping with data transfer. 406 AGRICULTURAL AND POOD SCIENCE IN FINLAND References Baker, R.J. 1971. Effects of stem rust and leaf rust of wheat on genotype-environmentinteraction for yield. Canadian Journal of Plant Science 51: 457-461. - 1990. Crossover genotype-environmentalinteraction in spring wheat. In: Kang, M.S. (ed.). Genotype-by- environment interaction and plant breeding. Louisi- ana State University Agricultural Center, p. 42-51. Dyke, G.V., Lane, P.W. & Jenkyn, J.F. 1995. Sensitivity (stability) analysis of multiple variety trials, with spe- cial reference to data expressed as proportions or percentages. Experimental Agriculture 31: 75-87. Finlay, K W. & Wilkinson, G.N. 1963. The analysis of adaptation in a plant breeding programme. Austral- ian Journal of AgriculturalResearch 14: 742-754. James, W.C., Jenkins, J.E.E. & Jemmet, J.L. 1968. The relationship between leaf blotch caused by Rhyn- chosporium secalis and losses in grain yield of spring barley. Annals of Applied Biology 62: 273-288. Khan, T.N. 1987. Relationship between net blotch (Drechslera teres) and losses in grain yield of barley in Western Australia. Australian Journal of Agricul- tural Research 38: 671-679. - & D’Antuono, M R 1985. Relationship between scald (Rhynchosporium secalis) and losses in grain yield of barley in Western Australia. Australian Journal of AgriculturalResearch 36: 655-661. Littell, R.C., Freund, R.J. & Spector, P.C. 1991. SAS Sys- tem for Linear Models. Third Edition, Cary, NC. 329 p. Mäkelä, K. 1974. Occurrence of Rhynchosporium seca- lis (Oud.) J.J. Davis on spring barley and winter rye in Finland. Journal of the Scientific Agricultural Soci- ety of Finland 46: 103-117. - 1975. Occurrence of Helminthosporium species on cereals in Finland in 1971-1973. Journal of the Sci- entific Agricultural Society of Finland 47: 181-217. Mathre, D.E, 1982. Compendium of barley diseases. American Phytopathology Society, St. Paul, Minne- sota, USA. 78 p. Mukula, J. 1988. The effect of climatic variations on bar- ley yield. In: Parry, M L. et al. (eds.). The Impact of Climatic Variations on Agriculture, Vol. 1: Kluwer Academic Publishers, p. 547-583. - & Rantanen, O. 1989. Climatic risks to the yield and quality of field crops in Finland VI. Barley 1969-1986. Annates AgriculturaeFenniae 28: 29-36. Nissilä, E. 1992. Yield stability of barley under Finnish conditions. Acta Agriculturae Scandinavica42: 152- 157. - 1996. Relationships between phenotype and geno- type-environmentinteractions and their influence on yield in highly adaptedbarley germplasm. Ph.D. the- sis, University of Helsinki, Finland. 107 p. Robinson, J. & Jalli, M. 1996. Diversity among Finnish net blotch isolates and resistance in barley. Euphyti- ca 92: 81-87. - , Lindqvist, H. & Jalli, M. 1996. Genes for resistance to Finnish isolates of Rhynchosporium secalis. Eu- phytica 92: 295-300. Saari, E.E. & Prescott, J.M. 1975. A scale for appraising the foliar severity of wheat diseases. Plant Disease Reporter 59: 377-380. Saarikko, R.A. & Carter, T.R. 1996. Phenological devel- opment in spring cereals: response to temperature and photoperiod under northern conditions. Europe- an Journal of Agronomy5: 59-70, SAS Institute Inc, 1989, SAS/STAT User's Guide. Ver- sion 6, Fourth Edition, Volume 2, Cary, NC. 1686 p. Shipton, W.A., Boyd, W.J.R. & Ali, S.M. 1974. Scald of barley. Reviews in Plant Pathology 53: 839-861. - , Khan, T.N. & Boyd, W.J.R. 1973. Net blotch of bar- ley. Reviews in Plant Pathology52: 269-290. Tottman, D.R. & Makepeace, R.J. 1979. An explanation of the decimal code for the growth stages of cereals, with illustrations. Annals ofApplied Biology 93: 221- 234. Vivar, H.E., Burnett, P.A. & Bowman, J.E. 1987. Breed- ing barley for multiple disease resistance. Barley Genetics V, Proceedings of the Fifth International Barley Genetics Symposium, Okayama, Japan, p. 615-623. 407 Vol. 6 (1997): 399-408. AGRICULTURAL AND POOD SCIENCE IN FINLAND Robinson, J. & Jalli, M. Grainyield, net blotch and scald ofbarley SELOSTUS Ohrasato ja verkko- ja rengaslaikku virallisissa lajikekokeissa Jonathan Robinson ja Marja Jalli Maatalouden tutkimuskeskus Suomen virallisten lajikekokeiden ohrakokeiden (Hordeum vulgäre L.) satotulokset ja verkkolaikun (Pyrenophora teres Drechs./. teres Smedeg.) ja ren- gaslaikun (Rhynchosporium secalis (Oud.) J.J. Davis) määrä analysoitiin tautien esiintymisen määrittämi- seksi sekä taudin, genotyypin ja ympäristön satovai- kutuksen selvittämiseksi. Lisäksi tutkittiin sään vai- kutusta verkkolaikun ankaruuteen. Genotyyppi-koepaikka yhdysvaikutus oli tilastol- lisesti merkitsevä sadon mutta ei verkkolaikun esiin- tymisen suhteen. Verkkolaikun ankaruus vaihteli vuo- sittain mutta ei koepaikoittain. Verkkolaikun määrä kasvukauden lopussa oli suhteellisen pieni Saana- ja Thule-lajikkeilla eikä taudin esiintyminen ollut yhtä herkkä ympäristön vaikutukselle kuin esimerkiksi Tyra-lajikkeella. Arve oli oireiden perusteella alttein verkkolaikulle. Sen sato ei kuitenkaan kärsinyt tau- din esiintymisestä, minkä vuoksi sitä voi pitää verk- kolaikun kestävänä lajikkeena. Satotulosten ja verkkolaikun ankaruuden analysointi osoittaa, että genotyypin ja ympäristön yhdysvaikutuk- sen suuruutta ei voi selittää ohragenotyyppien verkko- laikunkestävyyseroilla. Rengaslaikun ankaruuden kes- kiarvolukemat olivat yleisesti pienempiä kuin verkko- laikun, ja sen merkitys näyttää verkkolaikkua vähäisem- mältä. Uusien koepaikkojen tulosten lisääminen verk- kolaikkutuloksiin ei muuttanut tehtyä johtopäätöstä verkkolaikun runsaamman esiintymisen ja suuremman sadon yhteydestä. Toukokuun sademäärä ja lämpötila- summa (yli O°C) vaikuttivat verkkolaikun määrään oh- rakasvustoissa kasvukauden lopussa. Ohran siementä ei Suomen virallisissa lajikekokeissa ole käsitelty kasvi- tautien torjunta-aineilla. Kylvö viileään ja märkään maa- han näyttää edesauttavan ohran orasten verkkolaikku- tartuntaa edellisvuonna tartunnan saaneestakasvijättees- tä vapautuvista verkkolaikkuitiöistä. Tulokset osoittavat, että kasvitautitulosten keräämistä virallisista lajikeko- keista on kehitettävä. 408 AGRICULTURAL AND FOOD SCIENCE IN FINLAND