Application effects of pathogenic soil inoculation method on resistance evaluation to banana fusarium wilt at seedling stage
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Abstract
【Objective】A stable and reliable method for the identification of banana resistance to fusarium wilt using pathogenic soil inoculation method at seedling stage was established in order to provide references for screening and evaluating banana germplasm resistant to fusarium wilt.【Method】By using Fusarium oxysporum f. sp. cubense 4(Foc4)as the tested pathogen,the susceptible banana cultivar Baxi seedlings were inoculated using irrigation inoculation,root soaking inoculation and pathogenic soil inoculation method. And the best inoculation method was select by comparing and analyzing the dynamic changes of pathogenic spore concentration and the incidence of plant disease. The resistance evaluation effects of the resistant or susceptible germplasms through counting incidence of plant disease were studied by using pathogenic soil inoculation under different Foc4 spore concentrations. The resistances of 31 banana germplasms were identified at seedling stage by pathogenic soil inoculation in order to investigate its evaluation effect.【Result】The changes of Foc4 spore concentration of planting medium,incidence rate and disease index of Baxi banana seedlings were greatly different with different inoculation methods. When taking pathogenic soil inoculation method,the concentration of Foc4 spores in the planting substrate remained stable at the original inoculation concentration of 1.0×106-1.1×106 spore/g soil throughout the experiment. With the root soaking inoculation method,the concentration of Foc4 spore in the planting substrate showed the change trend of increase first and then decrease;and Foc4 spore reached the maximum of 1.0×106 spore/g soil at day 21,decreased to 0.5×106 spore/g soil at day 28,and stabilized at 0.4×106 spore/g soil at day 35. With the irrigation inoculation method,the concentration of Foc4 spore in the planting substrate decreased rapidly from 1.5×106 spore/g soil to 0.5×106 spores/g soil during 0-14 d,and stabilized at 0.6×106 spores/g soil after 35 d. Furthermore,after 42 d of inoculation,the statistical results showed that the incidence rate and disease index of banana seedlings using pathogenic soil inoculation were the highest(98.9% and 67.3 respectively),and followed by root soaking inoculation(86.7% and 51.6 respectively);and those of the irrigation inoculation method showed the lowest(76.7% and 44.1 respectively). With pathogenic soil inoculation method,under the condition of Foc4 spore concentration of 1.1×104,1.1×105,and 1.1×106 spore/g soil,the incidence rates of highly susceptible banana cultivar Baxi were all more than 80.0%,and the incidence rates of highly resistant strain GCTCV-119 were 16.7%,35.6%,and 54.4% respectively. When the Foc4 spore concentration was 1.1×104 spore/g soil,both Baxi and GCTCV-119 had not present obvious appearance disease symptoms. Therefore,considering the incidence of highly susceptible and highly resistant cultivar(strain),the pathogenic soil inoculation method should take the concentration of Foc4 spores of 1.0×105-1.0×106/g soil. According to the evaluation results of 31 banana germplasms by pathogenic soil inoculation,there were 11 moderately resistant germplasms,14 susceptible germplasms and 6 highly susceptible germplasms.【Conclusion】The pathogenic soil inoculation method is stable,accurate, high efficient,simple and operable,and could be used as an optimal method for banana seedling fusarium wiltresistance evaluation and resistant seedling screening.
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