Diss. (sammanfattning) Stockholm : Karol. inst., 2001. / Härtill 5 uppsatser.

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The nature of microbial antagonism towards Fusarium culmorum and Microdochium nivale, the primary pathogens implicated in Fusarium seedling blight of wheat, was assessed in laboratory, controlled environment chamber and semi-field experiments. Dual culture experiments, using five different agar media, suggested that three Trichoderma species, Gliocladium roseum, G. catenulatum, Idriella bolleyi and a Finnish fungal isolate, J76, were the most effective of the 30 microorganisms tested in inhibiting mycelial growth of F. culmorum and/or Mnivale. Seedling tests showed that isolates of Gliocladium roseum, G. catenulatum and J76 were the most promising fungi in reducing Fusarium seedling blight on wheat plants. Isolates of these three fungi significantly reduced pre-emergence and post-emergence seedling death and disease severity, measured as the degree of stem base browning. In vitro, Groseum and G. catenulatum culture filtrates were highly inhibitory to mycelial growth of F. culmorum and Mnivale and also reduced germination of pathogen spores by approximately 9 0%. Culture filtrates of J76 partially inhibited F. culmorum and M. nivale spore germination but had no effect on mycelial growth. Thin layer chromatography (TLC) of a G. roseum culture extract showed nine UV-visible bands of which four displayed antibiotic activity towards F. culmorum. A G. catenulatum culture filtrate produced six UV-visible bands of which two significantly inhibited F. culmorumm ycelial growth. Volatile antibiotics inhibitory towards M. nivale in vitro were produced by isolates of G. roseum, G. catenulatum and J76. A scanning electron microscope (SEM) study showed that isolates of G. roseum, G.c atenulatum and J76 were necrotrophicm ycoparasites of F. culmorum and M. nivale, killing host cells by direct hyphal contact and causing localised disintegration of the host, probably by enzymatic attack.

Thesis (M.Sc.) --University of Adelaide, 1949. / Typewr. copy.

The relevance of drought and salinity stress under Mediterranean conditions is reviewed and prospects for crop improvement against these constraints are discussed. Field trials under severe drought in Syria highlighted the importance of earliness to ensure satisfactory yields. Peduncle length and frost tolerance were also important attributes. Under more favourable conditions in Sicily, the yield components per se (number of spikes, number of kernels and kernel weight) had greater influence on genotype performance. At both locations of evaluation high yields were attained through different architectures of traits. Durum wheat genetic resources proved very variable. Genotypes were identified which could be used as donors of adaptive characters in breeding programmes. The CERES-Wheat growth model was used for the two locations, using historical weather data and two genotypes of known adaptation to the region. Early heading was a positive attribute, particularly in Syria. At both sites, lengthening of the grain filling period resulted in higher yields. Three sowing dates were simulated. "Early" sowing (1 November) had the highest simulated yield in both environments, suggesting a possible agronomic means to improve yields under stress. Simulated yields were in most cases within 15% of measured values when a comparison was possible. The ability to adjust osmotically was sought in seedlings artificially exposed to drought stress during early development. One entry appeared to possess this feature. However, another genotype, of known tolerance under real conditions, did not show this ability. Therefore, osmotic adjustment during early stages of ontogeny does not seem unequivocally able to identify the best genotypes under drought. Salt tolerance of durum wheat genetic resources was assessed measuring early growth under controlled environment. The data indicated that the results may be somewhat experiment-specific when using different growing techniques such as hydroponics and sand-culture. Finding tolerant tetraploid entries in terms of plant survival and ion uptake seemed difficult. However, variability existed and some entries, less susceptible than others, were noted. They could be used for breeding. For instance, they could be valuable recipient for the introgression of identified resistance mechanisms from other taxa.

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