Vol. 6 (1997): 199-205. Research Note Drought response of modern and old oat lines in greenhouse and long-term field trials Pirjo Mäkelä, Leena Väärälä, Riikka Rajalahti, Ari Rajala, Pirjo Peltonen-Sainio Department afPlant Production, Section ofCrop Husbandry, PO Box 27, FIN-00014 University ofHelsinki, Finland, e-mail: pirjo.pellonen-sainio@helsinki.fi This study compares the response of old and modern oat (Avena sutiva L.) lines to pre-anthesis pre- cipitation in long-term field trials, and to pre- and post-anthesis drought in the greenhouse. Long- term field trials were carried out at the Experimental Farms of Hankkija Plant Breeding Institute and the University of Helsinki between 1965 and 1988. Grain yield of 12 oat lines (released since 1959) was compared with that of the check lines. The effect of differences in May-June precipitation on grain yield was established for different lines. Greenhouse experiments included 19 oat lines (re- leased since 1921) and three wild species of oat (A. barbata L., A. sterilis max. L. and A. fatua L.). The data from greenhouse experiments were analysed using discriminant analysis in groups of old (released before 19705), modern, and wild oat types. Ranking of the oat lines according to results from long-term field trials and greenhouse experiments was not consistent; contrary to the field ex- periments, the old lines tended to be the most drought sensitive when tested in the greenhouse. There- fore, the simple and non-laborious methods used in this study for ranking of drought sensitivity of oat lines are not recommended. Key words'. Avena ssp., cultivar ranking, drought tolerance, grain yield, physiology ntroduction The results from long-term oat cultivar trials in Finland have indicated that grain yield has in- creased through plant breeding by 30-40% (Rekunen 1988, Peltonen-Sainio and Karjalai- nen 1991). This can be attributed to a higher grain to straw ratio following selection for short straw, and high weight and filling rate of the panicle (Peltonen-Sainio 1990). This may con- tribute to drought sensitivity because plant height often correlates with root depth, and most root mass of the short-strawed cultivars is concen- trated in the topsoil (Mac Key 1988). Postulated changes in drought sensitivity are emphasized due to early summer drought that is characteris- tic in southern and south-western Finland (Mukula and Rantanen 1989). Considerable effort has been made to devel- op reliable and rapid methods for screening for cultivar differences in drought tolerance. Expres- sion ofdrought resistance is associated with nu- merous changes in plant phenology, morpholo- © Agricultural and Food Science in Finland Manuscript received November 1996 199 AGRICULTURAL AND FOOD SCIENCE IN FINLAND https://www.c-info.fi/en/info/?token=X9t-BHB-e5M3O46B.quBu1pjGo9nkVyO3HkP4_g.QWLXXPTOmkew5p5Peces4nEufJQxnTB37mUWQIBGvB81SeewjiDemrUaQzL4sM3ne0hPTeEmrVgdoX-RHmwuEJoxgPpN0CPI0DnXZ01lmFQo6LTHp1vl0AKRrfXD3ZSrzW1kGqIlOlzKw7DckDF2CAX5DAVzhVXLSiNoHn-T0LO_6yeSn1Z5cQQv1TjV0SN8n3beVFY5ThTVVqn_kf3Nn3DChjBGNCPEWs543i1qXBCsvbQIqbxIQh2nw2QtwOK5IT3ps3ycYgLeDNzcYYUjpjtPxNALCxXLfJV5E9kJ9zZFt0yY2CZ7Kgn9Cm7jKir2zwmSWG9fMm9psCdnmJ0_GYDBJfl0bGE0WA64mXbKoaGZDuUYkbeivHwmjmYG_e81WGuy-vI Mäkelä, P. et al. Drought response ofoat lines gy, and physiology (Larsson and Gorny 1988), which makes its evaluation very complex and ranking of cultivars often inconsistent. Extrapo- lation of drought tolerance from long-term field experiments is a rapid method for evaluating cultivar differences, but differences may be masked due to numerous factors other than pre- cipitation which cause variation in grain yield. Comparison of grain yields produced in favour- able versus drought-stressed environments, simulated in a controlled environment, possibly represents a more accurate method for evaluat- ing differences in drought tolerance. This study compares the response of old (released before 19705) and modern oat lines to pre-anthesis pre- cipitation in long-term field trials and to pre- and post-anthesis drought simulated in the green- house. Material and methods Long-term field trials were carried out at Antti- la (60°25’N), Nikkilä (61°33’) ; and Viskaali Ex- perimental Farms (64°53’), Hankkija Plant Breeding Institute, Finland, in 1965-1988 (Hankkijan kasvinjalostuslaitos 1965-1989), and Viikki Experimental Farm (60°13’N), Universi- ty of Helsinki, Finland, in 1988-1993. Grain yield (g nv2 , at 15% moisture content) of eight Finnish [Hankkijan Vouti (released in 1982), Hannes (1964), Kyrö (1959), Puhti (1978), Ryhti (1970), Sisu (1948), Veli (1981), and Virma (1988)] and three Scandinavian [Pol (1974), Svea (1979), and Karhu (=Stil, 1985)] oat cultivars in addition to one breeding line (Hja 76416), were compared with the long-term check lines Ryhti (1961-1973) and Puhti (1974-1988). Ratio be- tween Ryhti and Puhti in grain yield was estab- lished with >3OO experiments. The number of experiments included in this comparison varied between oat lines (from 70 to 200 experiments). May and June precipitation (mm) was recorded at each trial site and ranged from 40 to 188 mm during the study period. Three greenhouse experiments were conduct- ed at the Department of Plant Production, Uni- versity of Helsinki, Finland. Day-length was 18 hours at light intensity (PAR) of about 200 |imol m' 2 s l . Day and night temperatures were respec- tively 20°C and 17°C. The same oat lines that were included in the long-term field experiments and seven additional lines [Esa (1922), Jalostet- tu maatiainen(1921), Kytö (1925), Osmo (1921), Pellervo (1935), and breeding lines Hja 76420 and Hja 77200] were tested in the greenhouse. Wild species of oat Avena sterilis max. and A. abyssinica were included in all experiments and A. fatua ('Laihia') in experiment (exp) 3. Seeds were pre-germinated on moist blotting paper for two days at 20°C before sowing. In total 22 pre- germinated seeds were placed in a 7.5 1 plastic pot containing peat-vermiculite mixture (1:1). Following emergence, seedlings were thinnedto 20. The pots were fertilized by top-watering eve- ry 14 days with a nutrient solution (500 ml 1%, N-P-K, Kemira Oy, Finland). The experiments included two treatments: 1) a control, where plants were continuously well- watered (200 to 500 ml per pot), and 2) drought stress. When simulating temporary and moder- ate pre-anthesis drought (exps 1 and 2), the oat stands were subjected to a water deficit for two weeks which was followed by adequate water- ing until yellow ripening. When severely drought stressed (exp 3), plants were subjected to water deficit for two days close to pollination and thereafter they were slightly stressed through- out grain-fill. The severity ofdrought was meas- ured using a test-tube (0 2 cm) to remove a soil core from each pot and determine the water con- tent. pF-values were determined based on soil water retention curves. Physiological measure- ments were carried out in exps 1 and 2 at the four-five leaf stage on the two uppermost fully expanded leaves, and in exp 3 on the flag leaf close to pollination. Photosynthetic parameters were measured on two plants per treatment, three measurements per leaf, with a LI-COR LI-6200 portable photosynthesis system (Licor Inc., NE, USA). The two uppermost fully expanded leaves of six plants in exps 1 and 2 and 15 flag leaves 200 AGRICULTURAL AND FOOD SCIENCE IN FINLAND Vol. 6 (1997): 199-205. in exp 3 were collected and endogenous absci- sic acid (ABA) concentration was measured as described by Peltonen-Sainio and Mäkelä (1995). Similarly, accumulation of proline was measured as described by Troll and Lindsley (1955) and Hanson et al. (1977). Relative water content (RWC) was evaluated on three and two uppermost fully expanded leaves in exps 2 and 3, respectively, according to Ritchie et al. (1990). Mature oat plants (14 per treatment, exps 1 and 3) were cut at soil-level, air-dried, and the total weight of grains per main shoot panicle (i.e., panicle weight) of each cultivar was measured. Statistical analyses Average grain yields over different field trials, in which May and June precipitation differedby < 5 mm, were calculated. To establish the culti- var response to early summer precipitation in long-term field trials, the grain yield ofeach line was calculated relative to the check cultivar in as many experiments as possible, and the results were interpreted according to Larsson (1982). In greenhouse experiments, response of oat lines to drought was compared by calculating indices. The index of each physiological trait was calcu- lated for each line by dividing the value for the trait measured under water deficitby thatrecord- ed under adequate watering. The greater the de- viation of each physiological index from 1, the greater the response of the specific line to drought stress. The data from greenhouse exper- iments, arranged in a groups of old (released before 19705), modern, and wild oat types, were analyzed by discriminant analysis (Statgraphics 1992). Results and discussion Differences among oat lines in response to early summer precipitation were moderate when ex- trapolated from long-term field trials (Fig. I). The regression coefficients for different oat lines ranged from -0.041 to 0.093. Therefore, 100 mm decrease in May-June precipitation resulted in 4.1% higher to 9.3% lower grain yield relative to Puhti (i.e., from ca. 180kg more to 400 kg ha’ 1 less grains, respectively). Grain yields of the modern lines Hankkijan Vouti, Karhu, Pol, Ryh- ti, and Veli, were reduced more than that of the long-strawed old cultivars Kyrö and Hannes due to reduced early summer precipitation. Virma and Sisu were exceptions to this tendency. Hja 76416 is a short-statured breeding line, characterized as one of the most stable in northern growing conditions (Peltonen-Sainio et al. 1993) but showed, however, average responsiveness to ear- ly summer precipitation. Discriminant analysis demonstrated differ- ences among the modern, old, and wild oat types in theirresponse to moderate pre-anthesis (exps 1 and 2) and severe post-anthesis drought (exp 3) simulated in the greenhouse. In exp 1, the re- sponse to pre-anthesis drought was recorded immediately after the first signs of loss of tur- gidity and in exp 2, after prolonging the effects of drought. The response of wild species (A. barbata and A. sterilis max.) differed from those of the cultivated oats (Fig. 2). In exp 1, this was mainly due to fewer drought-induced changes in their relative water content and stomatal conduct- ance of the uppermost fully expanded leaf blades, in exp 2, due to lower accumulation ofABA and proline, and more constant stomatal resistance and leaf temperature, and in exp 3, due to more constant stomatal resistance and better ability to fill grains under inadequate watering (Tables 1 and 2). Old oat lines tended to be least able to maintain high water content during early stages ofdrought, but according to discriminant analy- sis there were no differences between modern and old lines subsequently (see exps 1 and 2 in Fig. 2). However, mean values of indices for ABA and proline content, stomatal resistance, and leaf temperature (Table 2) indicated that, in general, the modern lines were slightly more ef- ficient than the old lines underdrought stress also in exp 2. When drought-stressed close to head- ing (exp 3), weight of grains per panicle was 201 AGRICULTURAL AND FOOD SCIENCE IN FINLAND Mäkelä, P. et al. Drought response ofoat lines Fig. 1.Effect ofearly summer pre- cipitation on grain yield of oat lines relative to long-term check cultivar Puhti. Means of grain yield for different precipitation values are calculated as running means over five successive data points. 202 AGRICULTURAL AND FOOD SCIENCE IN FINLAND Vol. 6 (1997): 199-205. Table 1,The results of discriminant analysis for indices of morpho-physiological traits in modem and old oat culti- vars and wild species of oat. Indices* Standardized coefficient DFI DF2 Exp 1: PWEI 0.44 -0.69 ABAI 0.57 -0.20 RWCI 1.40 0.22 CERI 0.55 1.31 RESI 0.32 0.57 CONI -0.87 -0.55 II Ml 0.10 -0.25 Relative percentage 72.8 27.2 Significance level 0.003 0.068 Exp 2: PWEI 1.70 0.89 ABAI -5.43 -0.14 PROI 6.67 -0.77 RWCI 2.77 0.56 CERI -2.98 0.11 RESI 4.68 1.30 CONI 1.05 2.30 11 Ml 4.94 -1.74 Relative percentage 89.3 10.7 Significance level 0.012 0.494 Exp 3: PWEI 8.83 2.77 ABAI -5.00 8.97 PROI -1.72 -3.00 CERI -1.01 3.68 RESI -8.04 1.61 CONI 4.06 -6.48 TEMI -1.65 5.24 Relative percentage 93.9 6.1 Significance level 0.050 0.855 # indices for RWCI, relative watercontent; CONI, stomat- al conductance; ABAI, abscisic acid concentration; PROI, proline concentration; RESI, stomatal resistance; TEMI, disparity between air and leaf temperatures; PWEI, panicle weight most reduced in the modern cultivars, but dif- ferences between the modern and old cultivars were modest. A. fatua did not shown any signs of improved drought tolerance. Larsson (1982) and Larsson and Gorny (1988) concluded that the most reliable ranking of oat lines according to theirresponse to water deficit is established by combining the results from field trials and greenhouse experiments. However, ranking of the oat lines according to long-term field trials and greenhouse experi- ments differed. For example, Hannes and Kyrö Fig. 2. Discriminant analysis plots forold, modern, and wild oat types. Discriminant functions, DFI and DF2 are char- acterized in Table 1.Wild oat: \=A. abyssinica, 2=A. steri- lis max., 3=A.fatua (exp 3 solely); Modern: 4=Hankkijan Vouti,s=Hja 76416,6=Hja 76420,7=Hja 77200,8=Karhu, 9=Pol, 10=Puhti, ll=Ryhti, 12=Svea, 13=Veli, 14=Virma; Old: 15=Esa, 16=Hannes, 17=Jalostettu maatiainen, 18=Kyrö, 19=Kytö, 20=Osmo, 21=Pellervo, 22= Sisu. 203 AGRICULTURAL AND FOOD SCIENCE IN FINLAND Mäkelä, P. et al. Drought response ofoat lines Table 2. Mean values of indices with highest loadings according to discriminant analysis for modem, old, and wild oat types. The greater the deviation of each index from 1, the greater the response of the specific oat type to inadequate watering. Indices* Oat type Modern Old. Wild Exp 1: RWCI 0.92 0.83 0.99 COM 0.14 0.09 0.15 Exp 2: ABAI 2.70 3.67 0.80 PROI 89.07 93.25 8.24 RESI 7.24 8.49 1.26 TEMI 0.25 0.1') 0.56 Exp 3: PWEI 0.36 0.42 0.67 RESI 7.81 15.00 2.08 # indices for RWCI, relative water content; CONI, stomatal conductance; ABAI, abscisic acid concentra- tion; PROI, proline concentration; RESI, stomatal resistance; TEMI, disparity between airand leaf temper- atures; PWEI, panicle weight identified as the most drought tolerant oat lines according to field trials, were among the most sensitive lines (exp 1) or were of average per- formance (exps 2 and 3) when tested in the green- house. Probably the main reason for the inabili- ty of the old cultivars to cope with pre-anthesis drought when tested in the greenhouse, is that growing them in pots masks the effect of root depth as a tolerance mechanism. However, evi- dently it is difficult to rank cultivars reliably based solely on the results from field trials, de- spite some differences in response of oat lines to pre-anthesis precipitation. Numerous factors other than precipitation cause variation in grain yield. This is possibly emphasized when testing modern cultivars solely and lacking such large intrinsic differences in plant stand structure as included in this study. Furthermore, comparing drought response of the most recently released cultivars may be restricted due to too few data points. Therefore, the simple and non-laborious methods represented in this study seem to be biased and are not suggested for use when rank- ing drought tolerance of oat lines. Acknowledgements. The authors are grateful to professor Erkki Kivi and directorgeneral Voitto Koskenmäki for kind- ly allowing us to use the data from field trials carried outat Hankkija Plant Breeding Institute References Hankkijan kasvinjalostuslaitos 1965-1989. Trial Results. Rekunen, M. (ed.). Hankkija Plant Breeding Institute. Hanson, A.D., Nelsen, C.E. & Evertson, E.H. 1977. Eval- uation of free proline accumulation as an index of drought resistance using two contrasting barley cul- tivars, Crop Science 17: 720-726. Larsson, S. 1982. A simple, rapid and non-destructive screening method useful for drought resistance breeding in oats (Avena sativa L). Zeitschrift fur Pllanzenzuchtung 89: 206-221. - & Gorny, A.G. 1988. Grain yield and drought resist- ance indices of oat cultivars in field rain shelter and laboratory experiments. Journal of Agronomy and Crop Science 161: 277-286. Mac Key, J. 1988. Shoot:root interrelations in oats. In: Mattsson, B. & Lyhagen, R. (eds.). 3rd International 204 AGRICULTURAL AND FOOD SCIENCE IN FINLAND Vol. 6 (1997): 199-205. Oat Conference. Lund, Sweden, July 4-8 1988. Svalöf, Sweden, p. 340-344. Mukula, J. & Rantanen, O. 1989. Climatic risks to yield and quality of field crops in Finland. VII. Oats 1969- 1986. Annates Agriculturae Fenniae 28: 37-43. Peltonen-Sainio, P. 1990. Genetic improvements in the structure of oat stands in northern growing conditions during this century. Plant Breeding 104: 340-345. - & Karjalainen, R. 1991. Genetic yield improvement of cereal varieties in northern agriculture since 1920. Acta Agriculturae Scandinavica 41: 267-273. - & Mäkelä, P. 1995. Comparison of physiological meth- ods to assess drought tolerance in oats. Acta Agri- culturae Scandinavica 45: 32-38. - , Moore, K., & Pehu, E. 1993. Phenotypic stability of oats measured with different stability analyses. Jour- nal of Agricultural Science, Cambridge 121: 13-19. Ritchie, S.W., Nguyen, H.T. & Holaday, A.S. 1990. Leaf water content and gas-exchange parameters of two wheat genotypes differing in droughtresistance. Crop Science 30: 105-111. Rekunen, M. 1988. Advances in the breeding of oats, comparative trials with historical varieties in 1977- 87. Journal ofAgricultural Science in Finland&o: 3o7- 321. Statgraphics 1992. Statistical Graphics System, Version 6.0. Troll, W. & Lindsley, J. 1955. A photometric method for the determination of proline. Journal of Biological Chemistry 215: 655-660. SELOSTUS Vanhojen ja uusien kauralajikkeiden reagointi kuivuuteen kasvihuone- ja peltokokeissa Pirjo Mäkelä,Leena Väärälä, Riikka Rajalahti, Ari Rajala, Pirjo Peltonen-Sainio Helsingin yliopisto Kasvinjalostus ja tutkimus kaipaavat nopeita ja yksinkertaisia menetelmiä kuivuudensiedon arvioi- miseksi. Tutkimuksessa verrattiin vanhojen (las- kettu kauppaan ennen vuotta 1970) ja uusien kau- ralajikkeiden kuivuudenkestävyyttä monivuotisten peltokokeiden ja kolmen kasvihuonekokeen perus- teella. Peltokokeissa kunkin lajikkeen jyväsato laskettiin suhdelukuna mittarilajikkeisiin. Kokeet jaettiin eri ryhmiin touko-kesäkuun sademäärän perusteella ja kullekin ryhmälle laskettiin suhdeluvun keskiarvo. Touko-kesäkuun sademäärän vaikutusta lajikkeiden suhteelliseen jyväsatoon kuvattiin käyrillä. Kasvihuo- nekokeissa kauralajikkeet altistettiin kuivuudelle pen- somisvaiheessa tai röyhylle tulon yhteydessä. Lajik- keiden herkkyyttä reagoida kuivuuteen verrattiin fy- siologisten ominaisuuksien perusteella lasketuista in- dekseistä (kuivuusstressioloissa saatu tulos jaettuna kontrollikoejäsenen tuloksella). Mitä enemmän in- deksi poikkesi arvosta yksi, sitä voimakkaammin ky- seinen lajike reagoi kuivuuteen. Peltokokeet osoittivat, että useat uudet lajikkeet reagoivat vanhoja herkemmin alkukesän kuivuuteen. Virma ja Sisu olivat poikkeuksia. Kasvihuonekokei- den perusteella vanhojen ja uusien lajikkeiden erot- telu oli vaikeaa ja suuntaus näytti olevan jopa päin- vastainen kuin peltokokeissa. Kasvihuonekokeessa kaurat kasvatettiin 7,5 litran purkeissa, jolloin syvä- juurisuus kuivuudensietomekanismina jäi huomiotta. Myös peltokokeista saatu tieto lajikkeiden reagoin- nista alkukesän sademäärään saattaa olla harhainen, koska sademäärän lisäksi useat muut tekijät vaikut- tavat sadontuottoon. Koeaineiston tuleekin olla laaja luotettavan käsityksen saamiseksi, mikä usein rajoit- taa jalostusaineiston kuivuuden siedon arvioimista. Näistä syistä tässä tutkimuksessa käytettyjä yksinker- taisia menetelmiä ei voida suositella käytettäväksi lajikkeiden kuivuusherkkyyden selvittämiseksi. 205 AGRICULTURAL AND FOOD SCIENCE IN FINLAND