Milan Pospišil

Environmental and management effects on grain quality of maize hybrids

Maize yield and quality responses to N and plant populations were significantly affected by environmental conditions. However, hybrid-specific differences in grain protein and oil contents were consistent in all environments and regardless of contrasting N fertilization rates and plant populations, showing the importance of hybrid selection for Croatian farmers.

Influence of sowing density on agronomic traits of lupins (Lupinus spp.).

The aim of the research conducted on eutric brown soil on the experimental facility of Faculty of Agriculture, University of Zagreb in 2012 and 2013, was to determine the optimal sowing density for two cultivars of white lupin (Teodora and Energy) and a cultivar of narrow-leafed lupin (Arabella). The study included three sowing densities: 60, 75 and 90 germinated seeds/m2. The cultivars of white lupin achieved significantly higher seed yield, higher 1000 seed weight, higher weight of seeds per plant and higher protein content in the seed, compared to the cultivar of narrow-leafed lupin. The sowing density had no effect on seed yield, but the increase in sowing density above 60 germinated seeds/m2 significantly reduced the number of pods, the number of seeds and seed weight per plant.

The influence of stages of maturity on the agronomic traits of fibre flax introduced varieties

The harvest time of fibre flax is influenced by climatic conditions, varieties, stages of maturity and the crop’s final use. In addition, the time of harvesting of fibre flax affects the quality of the fibres. Fibre flax can be harvested in few stages of maturity. So, this paper presents the influence of three stages of maturity (green, yellow and full ripening) on the agronomic traits (stem yield, stem yield after retting, total fibre yield, share of total fibre, long fibre yield, share of long fibre) of five fibre flax varieties. Varieties trials with fibre flax were set up in two years (2010-2011) and in two locations: at the experimental fields of the Faculty of Agriculture in Zagreb on eutric cambisol and of the College of Agriculture at Križevci on pseudogley on level terrain. The trials were carried out according to the randomized complete block design (RCBD) with four replications. According to the results of the two-years research into the agronomic traits of fibre flax, significant differences were established among the varieties and among the stages of maturity under study. The varieties Agatha, Viola and Electra recorded higher values of investigated traits. All varieties achieved higher values of investigated traits at Križevci (production on heavier soil in which some of winter moisture remained available in spring months). The highest values of investigated traits were recorded when the fibre flax were harvested in the green ripening.

First Report of Beet yellows virus (BYV) on Sugar Beet in Croatia

Sugar beet (Beta vulgaris var. saccharifera L.) is the main crop used for the production of sugar in Croatia. Beet yellows virus (BYV), type member of the genus Closterovirus, is characterized by flexuous, filamentous particles which are transmitted by several aphid species in a semipersistent manner (Agranovsky and Lesemann 2000). This widely spread virus is reported from most of the sugar beet-growing areas of the world, including Europe. In the geographic region that was once the former Yugoslavia, the presence of BYV was suspected based on field symptoms reported from Serbia (Nikolic 1951) and Croatia (Panjan 1951). During the 2013 and 2014 growing season, the presence of sugar beet plants with symptoms of yellowing was sporadically observed in commercial fields located in eastern Croatia (i.e., Tovarnik, Bosnjaci, and Virovitica). In late July 2014, a significant number of sugar beet plants, located mainly on the field edges, with the aforementioned symptoms were noticed in experimental fields of various sugar beet cultivars located at the University of Zagreb, Faculty of Agriculture. In total, 102 plants collected from commercial fields and 12 plants from the university experimental fields with cvs. Torda and Libero were selected and screened using ELISA for the presence of Beet necrotic yellow vein virus (BNYVV), Beet mosaic virus (BtMV), Beet mild yellowing virus (BMYV), Beet western yellows virus (BWYV), and BYV. To conduct the diagnostic assays, commercial ELISA kits from Loewe Biochemica GmbH (BNYVV, BtMV, and BYV) and Sediag (BMYV and BWYV) were used. BYV was confirmed in five plants from commercial fields and in all the plants from Zagreb. Due to the presence of single infections in plants from Zagreb, and in order to determine the detrimental effects of BYV, all plants from the study field control plots (104 of Torda and 103 of Libero) were tested by ELISA. Tests revealed the presence of BYV in 18 (17.3%) plants of Torda and in 34 (33%) plants of Libero. BYV infections averaged a 9 to 10% reduction of pure root yield and sugar content in both cultivars compared with BYV-free plants. One ELISA-positive plant per cultivar was chosen for the extraction of total RNA using the QIAGEN RNeasy plant mini kit according to manufacturer’s instructions. In both plants, the presence of BYV was confirmed by RT-PCR using four set of diagnostic primers (Kundu and Rysanek 2004). PCR products from both samples, named BYV- CRO-T from Torda and BYV-CRO-L from Libero, were purified and sequenced in both directions (Genbank Accession Nos. KP704263 to KP704268). Nucleotide sequence alignment of the DNA fragments for both Croatian isolates, including the C-terminal part of L-Pro and N-terminal part of MET and HSP70, showed 99.2, 99.7 and 100% similarity, respectively. Nucleotide comparisons of Croatian isolates with Californian (Genbank Accession No. AF056575) showed a 97% similarity for L-Pro and HSP70 and a 99% for MET. To our knowledge, this is the first report of Beet yellows virus in Croatia and its detrimental effect on actual sugar beet cultivars grown under Croatian environmental conditions.

Use of the bacteria Pseudomonas fluorescens in the control of sugar beet root decay agent — Rhizoctonia solani

In Republic of Croatia sugar beet is grown on approximately 30 000 ha, with an average yield of 37 t/ha and sugar content of 14, 4% Reasons for such a low production results after the Patriotic War are found in inadequate soil management, devastated soil structure, and climatic conditions. The result of the stated is high degree of disease development. Apart from beet leaf spot (C. beticola) and the disease induced by Rhyzomanie virus, the most serious issue is root rot of beet induced by pathogenic fungi (P. betae, P. ultimum, P. debarianum, R. solani, Fusarium spp., and A. cochlioides). Depending on the soil and climatic conditions, 10-50% of plants have been decaying being attacked by the pathogenic fungi. Growth of the surviving plants is slowed significantly giving them no possibility to reach normal size, which finally reflects on yield and sugar content values. Major measure in the control of sugar beet root decay agent is application of fungicides in the course of seed processing. However, though chemical fungicides prevent development of the fungi to some degree, they are at a disadvantage affecting human health and environment (being exposed to washing out, they give rise to underground water eutrophication). Moreover, pathogenic fungi have ability to rapidly develop resistance to the fungicides applied. Acceptable alternative to the application of chemical pesticides is seed inoculation with the bacteria P. fluorescens and T. harzianum that express antagonism against pathogenic fungi. Since the benefit bacteria do not express sensitivity to the low fungicide doses, on the soils heavily infected with the fungi – the root decay agents on sugar beet, positive effect was accomplished by combining seed inoculation with the bacterium P. fluorescens and the seed treatment with low doses of fungicides. Pathogenic fungi R. solani is found to be the most serious issue, so the influence of the bacterium P. fluorescens to the pathogenic fungi – the root decay agent of sugar beet, has been investigated.