Bio-ecological relations of sunflower pathogens - macrophomina phaseolina and fusarium spp. And sunflower tolerance to these pathogens

Macrophomina phaseolina, Fusarium solani and F. oxysporum are soil borne species which infect root, stem and collar region of plant host and cause cortical and vascular discoloration. There is need for identification of these pathogens at genus, species and isolate level. Fusarium spp. are mainly cosmopolites while M. phaseolina is prevalent in arid regions, but can be found in moderate climates when high temperature and dry conditions occur. The genera Macrophomina and Fusarium have some common hosts, such as sunflower, and tend to form mixed infections under favourable weather conditions. Coexistence of these pathogens, defining their relationship-type in a community and possibility of their additive pathogen effect, as well as dynamic of necrosis development on sunflower seeds were the aim of this research. Isolates of M. phaseolina and Fusarium spp. obtained from seven localities in Vojvodina (Northern Serbia), were tested in confronted colonies test and in pathogenicity test on three experimental sunflower hybrids. In the research, two types of interaction between M. phaseolina Fusarium isolates were registered. Isolates of M. phaseolina in comparison with Fusarium isolates had faster growth, which resulted in significant growth inhibition of Fusarium isolates during confrontation (41.11-50.36%). Among Fusarium spp. isolates, the least pathogenic were isolates originated from Kustin (41.92% and 40.06%), while the most pathogenic on sunflower seeds of all three hybrids tested was isolate from Pancevo (79.08%). Fusarium isolate from Pancevo was also the most aggressive in the confronted colonies test. The most pathogenic, on all three sunflower hybrids, of all M. phaseolina tested isolates, was isolate from Zrenjanin (68.14%), while the least pathogenic was isolate from Rimski Sancevi (47.37%). No additive pathogenic effect on sunflower seeds in a test with mixed pathogen suspensions was observed. Among three tested hybrids, NS-H-V4 was the most susceptible to Fusarium spp. and combinations of Fusarium + M. phaseolina, while NS-H-P3 was the most susceptible to M. phaseolina. Necrosis development dynamic was more dependent on resistance level of the hybrid than on the pathogen species