Fungal nonribosomal peptide synthetases (NRPSs) are responsible for the biosynthesis of numerous metabolites which serve as virulence factors in several plant-pathogen interactions. The aim of our work was to investigate the diversity of these genes in a Fusarium graminearum sequence database using bioinformatic techniques. Our search identified 15 NRPS sequences, among which two were found to be closely related to peptide synthetases of various fungi taking part in ferrichrome biosynthesis. Another peptide synthetase gene was similar to that identified in Aspergillus oryzae which is possibly responsible for the biosynthesis of fusarinine, an extracellular iron-chelating siderophore. To our knowledge, this is the first report on the identification of a putative NRPS gene possibly responsible for the biosynthesis of fusarinine-type siderophores. The other NRPSs were found to be related to peptide synthetases taking part in the biosynthesis of various peptides in other fungi. Transcription factors carrying ankyrin repeats were observed in the vicinity of four of the identified peptide synthetase genes. Additionally, NRPS related genes similar to putative long-chain fatty acid CoA ligases, acyl CoA ligases, ABC transport proteins, a highly conserved putative transmembrane protein of Aspergillus nidulans, and alpha-aminoadipate reductases have also been identified. Further studies are in progress to clarify the role of some of the identified NRPS genes in plant pathogenesis.
Garlic was examined in field experiments conducted in central Serbia (Belgrade). Spring garlic was examined. The objective was to examine the effect of plant density on photosynthesis productivity (LAR-Leaf Area Ratio, NAR- Net Assimilation Rate) and the yield of garlic. The analysis involved the following plant densities: 300 (G1), 450 (G2), 600 (G3), 750 (G4) and 900 (G5) thousand plants ha-1. The garlic exhibited better results in denser crop establishment. It is clearly indicated by the yield of garlic attained in the experiments. Average yield rates range from 5.6 (G1) to 12.5 t ha-1 (G5). The results demonstrate that the garlic should be grown in high density establishment.
Results of our experiments prove that pear is more or less sensitive to the reduced bee pollination period. However, the reaction (or the sensitivity) of cultivars may be different to the reduced bee pollination. Most cultivars produce much less yield under reduced bee pollination or no yield with the exclusion of bees but in the case of some cultivars total exclusion of bees does not prevent the yield formation and what is more sometimes reduced bee pollination can be resulted in somewhat higher yield than open pollination. Typical reaction, however, is a significant yield reduction with reduced bee pollination. Pear seems to be somewhat less sensitive to the partial reduction of bee pollination period than apple or quince. The first half of the flowering period seems to be more important in yield formation because usually higher yield was resulted when pear cultivars received open pollination in the first than in the second half of the blooming period. Based on our experimental results no definite relationship between parthenocarpic capacity of cultivars and the yield under reduced bee pollination can be established. So reduced bee pollination does not seem to contribute the parthenocarpic fruit formation in pear.
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