Figure 1 - uploaded by Regina Maria Villas Bôas de Campos Leite
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The expansion of sunflower can be affected, among other factors, by the presence of diseases, since it hosts over 30 phytopathogenic microorganisms, mostly fungi, which may, depending on climatic conditions that favor the occurrence of pathogens and the infective process, lead to a significant reduction on yield and quality of product. Alternaria l...
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... initial symptoms on leaves are small necrotic lesions with 3 to 5 mm diameter, variable color from brown to black, and round to angular chlorotic halo ( Figure 1). Characteristic lesions exhibit concentric circles, similar to a target. ...
Citations
... It is well known that a large number of species of pathogens of various origins are parasitic on sunflower. The most numerous are fungal diseases, the number of which is constantly growing (Gulya et al., 1997;Leite, 2014). ...
The genus and species composition of the micromycete complex in the root zone (rhizoplane, rhizosphere and edaphosphere) of sunflower at the beginning of flowering and full maturity stages during its cultivation on leached chernozem was studied. It was established that representatives of the genera Aspergillus, Botrytis, Gliocladium, Fusarium, Paecilomyces, Penicillium, Rhizopus and Trichoderma formed the complex of typical fungi of the rhizoplane and rhizosphere. At the stage of flowering in the mycocenosis, the species Paecilomyces lilacinus, Paecilomyces variotii and Trichoderma viride dominated, and in the maturity stage Rhizopus nigricans, Penicillium nigricans, Botrytis cinerea and Fusarium moniliforme var . subglutinans prevailed. The phytopathogenic complex at the flowering stage formed the species of the genera Fusarium and Rhizopus , and by the end of the vegetation the variety of potential pathogens was expanded by representatives of the genera Alternaria, Botrytis and Gliocladium . A comparative analysis of the micromycete complex revealed a similarity of the dominant species of the rhizoplane and rhizosphere in different stages of sunflower development. However, by the end of the vegetation in the rhizosphere, compared to rhizoplane, the abundance of fungi of the species Fusarium moniliforme var. subglutinans and Penicillium nigricans increased significantly. As for edaphosphere, Rhizopus nigricans, Trichoderma viride and Penicillium nigricans dominated during sunflower flowering, and by the end of the crop vegetation the number of micromycetes of the genus Fusarium was reduced while the proportion of micromycetes of the genus Rhizopus increased significantly.
The foliar fungal disease Septoria leaf spot is economically important for sunflowers. It develops most intensively during the wet and warm season. However, the genetic nature of sunflower resistance to Septoria leaf spot is still not clear. The purpose of our work was to identify some inheritance patterns of sunflower resistance to this disease based on the assessment of lines and hybrids of the first and second generations. The studied material was sown in 2020 and 2021 and subsequently grown on a stationary artificial infectious plot enriched with Septoria helianthi pathogen. The frequency of infection and the severity of infection of each sample were taken into account. The two-factor variance analysis revealed a significant influence of genotype on the frequency of infection in six sunflower lines and confirmed the effect of individuality of the response of individual genotypes to disease damage. It was shown that about 65 % of the total variation of the trait is due to the genetic nature of the line, and only a little more than 20 % and about 11 % – to the influence of the environment and the “genotype × environment” interaction respectively. Based on disease damage data in 2020 and 2021, the lines were classified as susceptible, moderately susceptible, moderately resistant and resistant. Differentiation of lines according to sensitivity to Septoria leaf spot made it possible to obtain hybrids with different manifestations of the trait in their parents. The nature of inheritance of infection frequency in F1 sunflower hybrids was determined by the degree of dominance. As a result, it was revealed intermediate inheritance, as well as positive and negative overdominance of the trait. The severity of infection by S. helianthi pathogen in F1 hybrids was inherited according to the type of parental form with greater resistance to the disease. F2 populations were found to inherit infection frequency from the more resistant parent, showing a proportion of infected plants similar to that of the more resistant line from a given cross combination. It has been shown that the frequency of infection of the F2 population with Septoria leaf spot can be affected by the severity of infection of F1 plant with the pathogen S. helianthi.
The investigation was carried out at Dobrudzha Agricultural Institute – General Toshevo, Bulgaria, and encompassed the period 2009–2010. The experiment involved four double haploid fertility restorer lines (DH-R-2, DH-R-7, DH-R-116 and DH-R-128), which have shown in our previous studies various degree of resistance to Sclerotinia sclerotiorum de Bary under artificial infection conditions. Ten plants from each investigated line were inoculated by the Straw-method at stage 5-6th pair of leaves. The plants were self-pollinated and the seeds obtained from them, as well as the seeds from the check plants (not infected), were analyzed for the traits 1000 seed weight, % of kernel, oil in kernel and protein content in kernel. Variations in the quality characteristics of the sunflower seeds were found in all investigated lines, the degree of quality “deterioration” having different expression according to the tolerance of the line to the pathogen. Lines DH-R-2 and DH-R-7 formed seeds with lower seed weight and percent of kernel. These seeds had lower oil and protein content. The established variations in the quality of the seeds between lines DH-R-116 and DH-R-128 and the check variants were not statistically significant.
