Components of quantitative resistance in sunflower (Helianthus annuus) to Plasmopara halstedii, the pathogen causing downy mildew, were investigated. Percentage infection, latent period, sporulation density and reduction of hypocotyl length were compared on two sunflower lines showing different levels of quantitative resistance in the field infected with different P. halstedii strains of races 100, 300, 710 and 714 in controlled conditions. The inbred line BT, rather susceptible in the field, showed a higher percentage infection, a higher sporulation density, a shorter latent period and less reduced hypocotyl length than inbred line FU, which showed a greater resistance in the field. The very good resistance of inbred line FU observed in the field was confirmed by the measurements of quantitative resistance criteria described in this study. Percentage infection of FU was 1.4% less than BT, latent period of BT was 12.4% less than FU, sporulation density of FU was 22.3% less than BT and reduced hypocotyl length of BT was 15.3% less than FU. It seems that the criteria such as latent period, sporulation density and reduction of hypocotyl length may be used to measure quantitative resistance in sunflower to P. halstedii.
The present study was carried out to investigate the compression loading behaviour of five Indian sunflower varieties (NIRMAL-196, NIRMAL-303, CO-2, KBSH-41, and PSH-996) under four different moisture levels (6-18% d.b). The initial cracking force, mean rupture force, and rupture energy were measured as a function of moisture content. The observed results showed that the initial cracking force decreased linearly with an increase in moisture content for all varieties. The mean rupture force also decreased linearly with an increase in moisture content. However, the rupture energy was found to be increasing linearly for seed and kernel with moisture content. NIRMAL-196 and PSH-996 had maximum and minimum values of all the attributes studied for both seed and kernel, respectively. The values of all the studied attributes were higher for seed than kernel of all the varieties at all moisture levels. There was a significant effect of moisture and variety on compression loading behaviour.
Changes in shoot length during development of two hybrid cultivars and one population cultivar of oilseed sunflower were compared in 3-year trials. Effects of cultivar, climatic factors, sowing density, and fertilization on plant height were analysed. In the conducted experiments, hybrid cultivars had higher shoots than cultivar ‘Wielkopolski’ since the first studied developmental stage (star stage). However, the large plant height does not have a positive effect on their agronomic value. Results of this study show that sunflowers were the highest in 1999 at all developmental stages, which resulted from more favourable weather conditions and soil type. The lowest final plant height was recorded when sunflowers were grown on brown-earth soil. This study confirms that increased sowing density caused a stronger elongation of shoots since the earliest developmental stages.
The paper reports results of a morphological study of pollen grain of three varieties of Helianthus annuus: Wielkopolski population variety and two interline hybrids Frankasol and Coril. The viability of the pollen grain was also determined. No significant differences were found between the population variety and the two interline hybrids.
Field experiments were carried out over 2002-2004 at the Experiment Station of the University of Technology and Agriculture at Mochełek, in the vicinity of Bydgoszcz, on a very good rye complex soil. High biomass yields were recorded for all the nonpapilionaceous plants researched, grown in stubble intercrop. Upon no nitrogen fertilization, sunflower showed to be most productive. The treatments which involved a high nitrogen dose (90 kg·ha-1) oil radish yielded significantly higher that phacelia. The plant produced also significantly more post-harvest residue mass than sunflower and phacelia, and also used nitrogen applied prior-to-sowing most considerably. An increase in the dose from 0 to 90 kg of nitrogen resulted in an increase in its accumulation in the plant biomass by 74.4 kg (82.7% of the nitrogen applied), as compared with the non-fertilized treatments. Sunflower used only 49.0 kg (54.4%), while phacelia – 48.2 kg (53.6%). The nitrogen fertilization applied in the experiments significantly increased the overground plant biomass yield of the crops researched. The greatest reaction to N fertilization was demonstrated by oil radish. The dry matter yield of this plant increased by 26.5% due to the application of 45 kg·ha-1, as compared with the yield collected from unfertilized objects. Increasing the nitrogen dose from 45 to 90 kg·ha-1 resulted in an 18.4% increase in the dry matter yield of radish. The effectiveness of nitrogen fertilization of sunflower was definitely lower and was, respectively, 14.6 and 7.0%. There was observed a relatively low infection with fungal pathogens in sunflower and phacelia, much higher in radish. A significant effect of the fertilization dose on the health status of the plant roots was found. Sunflower roots were most healthy when 45 kg·ha-1 was applied, and the most heavily infected when treated with 90 kg N·ha-1. Radish fertilization with nitrogen, irrespective of the dose, increased the root infection with fungi. There was found no clear effect of the nitrogen fertilization dose on the health status of phacelia roots. The pathogenic fungi isolated from infected roots of plants grown as intercrops were dominated by Alternaria alternata, as well as Fusarium spp., especially F. solani, F. avenaceum and F. culmorum.