Kevätvehnän Septoria nodorum -resistenssi taudinkestävyysjalostuksen näkökulmasta

Host-pathogen interaction between spring wheat and Septoria nodorum Berk. with applications for wheat breeding were studied. Ultrastructure of interactions was studied using electron microscopic techniques. Following inoculation, conidia of S. nodorum germinate, form appressoria anda penetration peg which directly penetrates through the cell walls. It is suggested that most penetration attempts fail because of cellular defence reactions, formation of papillae and cell wall alterations. Inoculation with low spore concentration reduced grain yield of Hankkija’s Taava cultivar by 10 % and 1000-grain weight by 14 %. Inoculation with high spore concentration on large plots of Tähti cultivar reduced grain yield by 32 % and 1000-grain weight by 18 %. Inoculation with high spore concentration on normal breeding plots of Tähti cultivar reduced grain yield by 35 % and 1000-grain weight by 21 % and the grain yield of Kadett cultivar by 27 % and 1000-grain weight by 20 %. Inheritance studies on F2 progenies of spring wheat crosses involving susceptible and moderately or highly resistant parents suggest that heredity component of symptom expression is moderate level and breeding success depends mainly on efficient screening techniques. Resistance was associated with tallness in crosses, and cultivar trials suggest that resistance is positively associated with late maturation time. Field screening techniques based on small plots and artificial inoculation showed that the most resistant entries were wild Triticum species and late and tall cultivars. Seedling plant tests based on attached seedling leaves and detached leaves revealed easily the most resistant and most susceptible cultivars. The overall correlation between seedling tests and field tests was quite high. The results are discussed in relation to wheat breeding strategies for resistance to S. nodorum.Tutkimuksessa tarkastellaan Septoria nodorum Berk. -sientä, joka aiheuttaa kellanruskeita laikkuja vehnän lehtiin ja varsiin sekä ruskettaa tähkän kaleita. Viime vuosina Septoria-tauti on lisääntynyt eri puolilla maailmaa ja aiheuttanut tuntuvia satotappioita. Suomessa sitä esiintyy koko vehnän viljelyalueella, ja sateisina kasvukausina sen lisääntyminen on ollut silmiinpistävää. Tautia voidaan osittain torjua kylvösiemenen peittauksella, vuoroviljelyllä ja fungisidiruiskutuksilla. Ulkomaiset kokemukset kuitenkin osoittavat, että resistenttien lajikkeiden viljely on tehokkain ja halvin torjuntamuoto. Tämän tutkimuksen tarkoituksena oli selvittää niitä perusedellytyksiä, joilla vehnän Septorian kestävyysjalostusta voitaisiin tehostaa. Elektronimikroskoopilla tutkittiin Septorian infektioprosessia ja osoitettiin, että sieni tunkeutuu kasviin suoraan soluseinän läpi. Sienen tunkeutuminen resistenttiin kasviin estyy osittain sen vuoksi, että resistentti solukko muodostaa tunkeutumiskohtaan tiiviin suojakerroksen, joka estää sienen etenemisen. Septorian vaikutusta kevätvehnän satoon tutkittiin useassa kokeessa. Vuoden 1981 kokeessa kohtalainen infektio alensi Hankkijan Taava-lajikkeen satoa 10 % ja 1000-siemenen painoa 14 %. Vuonna 1984 voimakas infektio alensi suurilla koeruuduilla tehdyssä kokeessa Tähti-lajikkeen satoa 32 % ja 1000-siemenen painoa 18 %. Toisessa vuonna 1984 tehdyssä kokeessa voimakas infektio alensi Tähti-lajikkeen satoa 35 % ja 1000 siemenen painoa 21 % sekä Kadett-lajikkeen satoa 27 % ja 1000-siemenen painoa 20 %. Tulokset osoittavat selvästi, että jo kohtalainen infektio alentaa tuntuvasti vehnän satoa. Septoria-taudin resistenssin periytyvyyttä tutkittiin F2-risteytysjälkeläistöstä, joka oli saatu risteyttämällä alttiita ja kestäviä lajikkeita. Tulokset osoittavat, että ympäristövaihtelu selitti toisissa risteytyksissä yli puolet taudin ilmenemisestä, mutta risteytyksissä, joissa toinen vanhempi oli erittäin kestävä, periytyvien osien määrät olivat sangen korkeita. Resistenssin havaittiin korreloivan positiivisesti kasvin pituuden ja myöhäisyyden kanssa, mikä vaikeuttaa jalostustyötä. Tämä tutkimus kuitenkin osoittaa, että kestävyysaineistoissa on kohtalaisen kestäviä aikaisia linjoja ja lajikkeita, joita voidaan hyödyntää pohjoisten alueiden kevätvehnän jalostuksessa. Kevätvehnälajikkeiden ja jalostuslinjojen Septoria-taudin kestävyyttä selvitettiin kenttä- ja laboratoriotestein. Kenttätestit osoittivat, että kestävimpiä olivat villit vehnät ja hyvin myöhäiset sekä pitkät lajikkeet. Eräät Pohjoismaissa viljellyt lajikkeet kestivät tautia kohtalaisesti, mutta suurin osa kotimaisista oli hyvin alttiita. Kasvihuoneessa testattiin kahdella menetelmällä lajikkeiden ja linjojen taudinkestävyyttä taimivaiheessa. Molempien testien avulla kyettiin nopeasti ja luotettavasti seulomaan altteimmat ja kestävimmät lajikkeet. Taimitestit korreloivat melko hyvin kenttätestien kanssa. Tutkimus osoittaa, että taimitestit voivat merkittävästi helpottaa jalostuslinjojen testausta, koska testit voidaan tehdä talvella. Keinotekoiseen saastuntaan perustuva kenttätesti on luotettava ja tehokas keino seuloa jalostuslinjoja ja jakautuvia varhaisia populaatioita

Benzothiadiazole induces the accumulation of phenolics in strawberry

We have studied the potency of benzothiadiazole against powdery mildew disease in strawberry under greenhouse conditions, where the disease can be a problem. The results show that, in addition to other cultivation techniques, BTH-induced resistance could be exploited to obtain fruits with higher amount of beneficial health compounds

Organic production: does it enhance the health-promoting compounds in berries?

We have analyzed phenolic compounds from organically and conventionally grown blackcurrants and strawberries to test the idea if organically grown berries contain a higher amount of health-promoting phenolic compounds

Yield reduction of spring wheat in relation to disease development caused by Septoria nodorum

Effects of Septoria nodorum on the grain yields and yield components of three spring wheat cultivars were studied in Finland using artificial field inoculation over three years. At low infection level, in 1986, grain yield was reduced in all cultivars by 2—10 %, but statistically insignificantly. In 1984 severe infection reduced the grain yields of cultivars Kadett and Tähti by 27 % and 32 %, respectively, while in 1985 the yield of Tähti was reduced by 16 % and that of Kadett by 18 %. Grain weights were reduced under low disease stress by 3—5 %, while under severe disease stress the reductions were 7—20 %. Disease strongly reduced the green-leaf area duration compared with fungicide-treated plots. Examination of single tillers showed that all yield components were significantly reduced. The disease amount on second leaves correlated best with grain weight loss. Implications of these results for controlling the damage caused by S. nodorum in spring wheat are discussed

Host-pathogen interaction between spring wheat and Septoria nodorum with reference to resistance breeding

Host-pathogen interaction between spring wheat and Septoria nodorum Berk. with applications for wheat breeding were studied. Ultrastructure of interactions was studied using electron microscopic techniques. Following inoculation, conidia of S. nodorum germinate, form appressoria anda penetration peg which directly penetrates through the cell walls. It is suggested that most penetration attempts fail because of cellular defence reactions, formation of papillae and cell wall alterations. Inoculation with low spore concentration reduced grain yield of Hankkija’s Taava cultivar by 10 % and 1000-grain weight by 14 %. Inoculation with high spore concentration on large plots of Tähti cultivar reduced grain yield by 32 % and 1000-grain weight by 18 %. Inoculation with high spore concentration on normal breeding plots of Tähti cultivar reduced grain yield by 35 % and 1000-grain weight by 21 % and the grain yield of Kadett cultivar by 27 % and 1000-grain weight by 20 %. Inheritance studies on F2 progenies of spring wheat crosses involving susceptible and moderately or highly resistant parents suggest that heredity component of symptom expression is moderate level and breeding success depends mainly on efficient screening techniques. Resistance was associated with tallness in crosses, and cultivar trials suggest that resistance is positively associated with late maturation time. Field screening techniques based on small plots and artificial inoculation showed that the most resistant entries were wild Triticum species and late and tall cultivars. Seedling plant tests based on attached seedling leaves and detached leaves revealed easily the most resistant and most susceptible cultivars. The overall correlation between seedling tests and field tests was quite high. The results are discussed in relation to wheat breeding strategies for resistance to S. nodorum

Spring wheat mixtures in northern crop production: ability of mixtures to buffer disease development and yield loss caused by Septoria nodorum

Epidemic development of Septoria nodorum was studied in pure stands and mixtures of two spring wheat cultivars Tähti (susceptible) and Kadett (moderately resistant) in 1983—1985. Apparent infection rates in the mixture were similar to that of the more resistant pure stand. In all three years, disease levels in mixed stands were lower than the arithmetic mean of the pure stands. The yield experiments indicated that under low or moderate disease stress mixtures can buffer yield reduction effectively. However, when disease levels were high, mixtures appeared to be less effective in that respect. The results are discussed in relation to possible mechanisms of intraspecific mixtures to retard non-specialized pathogens. The use of wheat mixtures to prevent disease induced yield losses caused by S. nodorum is also discussed

Yield reduction of spring barley in relation to disease development caused by Rhynchosporium secalis

Effects of barley scald caused by Rhynchosporium secalis on grain yield were studied in three spring barley cultivars under field conditions using artificial inoculation over three years. The disease strongly reduced the green-leaf area duration compared with fungicide-treated leaves. At low infection level, R. secalis reduced the grain yield of barley by 3—5 %. Moderate and severe infection reduced the grain yields of susceptible cultivars by 10—12 %. Single-tiller analysis of yield components indicated that grain weight and ear weight were most affected, but the number of grains was only insignificantly reduced by the disease. Implications of these results for controlling scald disease in Finland are discussed

Variation in protein content of peas under Finnish conditions

The variation of protein content and correlations between protein content and agronomic traits were studied on materials in variety trials over five years and at two locations in southern Finland. Protein content and protein yield of a given genotype varied widely in different years. High temperature during the growing season was the main climate factor influencing protein content. Statistically significant variation in protein content was found between different genotypes. Correlations between protein content and seed yield were weak, negatively significant in only two years. The relationship between seed weight and protein content was negative in all years. Late maturity was positively associated with protein content in all years and at both locations. It is suggested that breeding for protein productivity in northern conditions it is more effective to improve seed yield and yield stability than to attempt improving protein content

Environmental and genetic variation in protein content of peas under northern growing conditions and breeding implications

Association of protein content in peas with climatic factors was studied on data based on official cultivar trials at six locations in southern Finland in 1978—1985. Correlation and step-wise multiple linear regression methods were used to define the main climatic variables affecting protein content. Correlation studies showed that protein content was significantly and positively associated with temperature sum and mean June temperature and significantly negatively correlated with July precipitation. Regression analysis indicated that climatic factors accounted for 25 %—70 % of the total variation in protein content. Temperature sum and precipitation in July were the most important independent variables explaining protein variation. The role of environmental factors for protein variation and its implications for the improvement of protein content by plant breeding is discussed