Reduced Rhizoctonia solani and Streptomyces sp. infection by using combined microbial inocula on organic potato Orsolya Papp, Borbála Biró, Éva Abod, Tímea Jung, Imre Tirczka, Dóra Drexler
Introduction, objectives Organic agriculture: soil biological functioning and proper agrotechnical management are of key importance. Beneficial microbial inocula may help with: plant strengthening or protecting soil structure-improving Which type of microbes should be applied? How the soil microbial status and potato quality might respond?
Location, experiment 6-7 Potato (Solanum tuberosum var. Démon) Organic Research Station of SzIE (Gödöllő) Soil: sandy loam, ph: 7,4-7,8, H%: 3,3-3,6 Pre-crop: chickpea Nutrients: manure 5 t/ha Planting: 8. 4. (6), 7. 4. (7) Plant protection: (colorado beetle:) Bacillus thuringiensis, (Phytophtora:) CuOH Irrigation: spreading watering Harvest: 5. 8. (6), 9. 9. (7)
Treatments: inocula PPS treatment (CFU 8 /ml): - Pseudomonas protegens (PGPR) - Pseudomonas jessenii (PGPR) - Strenotrophomonas maltophylia (Biocontrol) ml/tuber TPB treatment (CFU 8 /ml): - Trichoderma hartianum (Biocontrol) - Pseudomonas putida (PGPR) - Bacillus subtilis (P+) ml/tuber PGPR: Plant Growth Promoting Rhizobacteria (siderophore, iron (Fe)- chelator-producers) Biocontrol: antagonism P+: phosporousmobilization Control treatment: ml water/tuber
Plot size: 9,3 m² (= 48 pc. tubers) Four replications, random block design
Measured parameters on potato plants: Chlorophyll activity (SPAD) Yield of plots (kg/m²) Size/weight of tubers: >35 mm; 35-6 mm; 6< mm Occurance of diseases (pc./ tb.): Streptomyces scabies, Rhizoctonia solani, and Fusarium sp. infection, greened and deformed tubers Starch content Method of statistical analysis: ANOVA
Results: SPAD measures * *
Yield
Yield fractions
Starch
Quality attributes * * * *
Measured soil parameters: Sampling 4 times: before planting, 3 weeks after planting, at flowering, at harvest. Soil enzymes: - DeHydrogenase enzym Activity (DHA) Abundance of microbes (MPN Most Probable Counts): - aerob/anaerob heterotrophs - Microscopic fungi - Pseudomonas sp. - Sporeforming bacteria
TPB ug/dry soil g TPF ug/dry soil g TPFµg/dry soil g TPFµg/dry soil g DH enzyme activity (DHA): years 6.6.8. 6.8.5. 6,5,5,5,5 Kontroll Control PPS TPB Kontroll Control PPS TPB 7.6.. 7.7.. 7,5,5,5,5 Control K PPS TPB Control K PPS TPB Strong annual variability in DHA. Much (~8-times) less activity in 7. The TPB inoculation increased DHA in 6, but not in 7.
(TPFµg/soil g) (TPFµg/soil g (TPFµg/soil g) DH enzyme activity (DHA) 6,5,5,5 6.5.. Control PPS TPB Enhanced activity with plant physiological status. The highest activity found at flowering. At harvest (autumn) it is equalised and reduced. TPB inoculation increased the DHA at the flowering stage in 6. 6.6.8. 6.8.5.,5,5,,,5,5,,,5,5, Control PPS TPB, Kontroll Control PPS TPB
MPN counts: aerobs and anaerobs 6 8 7 6 5 4 3 Aerob MPN 6.5. 6.6.8 6.8.5 6.5. 6.6.8 6.8.5 Control PPs TPB Control PPs TPB 8 7 6 5 4 3 Anaerob MPN 7 8 7 6 5 4 3 Aerob MPN 7.6. 7.7. 7.9.6 Cont PPS TPB 8 7 6 5 4 3 Anaerob MPN 7.6. 7.7. 7.9.6 Cont PPS TPB Seasonal and annual variability. There seem to be an inverse tendency between countable aerobs and anaerobs during the vegetation periods in 6.
MPN counts: fungi and Pseudomonas sp. 6 8 7 6 5 4 3 Fungi MPN 6.5. 6.6.8 6.8.5 Control PPs TPB 8 7 6 5 4 3 Pseudomonas MPN 6.5. 6.6.8 6.8.5 Control PPs TPB 7 8 7 6 5 4 3 Fungi MPN 7.6. 7.7. 7.9.6 Cont PPS TPB 8 7 6 5 4 3 Pseudomonas MPN 7.6. 7.7. 7.9.6 Control PPS TPB Seasonal and annual variability also. Higher (-times more) fungal counts in 7. Inoculation of TPB has increased fungal number in 7, and the PPS of the Pseudomonas counts in 6.
Results summary Plant: Tuber yield, yield fraction and starch content were not changed significantly by the treatments. There is annual variability in all results PPS: reduced Streptomyces infected tubers significantly in 7, but increased in 6. Increased Rhizoctonia infected tubers in 7. TPB: reduced Rhizoctonia solani infection on tubers in 6, but no effect on disease in 7. Soil: DHA enzyme activity is being in high relation with plant physiological status. The highest values are at the flowering stage. Affected soil microbial status with strong seasonal and annual variability. Type-dependent effect of inoculation to the MPN counts. Different response of studied microbial physiological groups.
Discussion - Conclusion PPS Consist of mainly siderophore producing (PGPR) type of bacteria with assumed effect for soil-borne plant pathogens: Pseudomonas protegens Pseudomonas jessenii Strenotrophomonas maltophylia TPB More complexity of inoculum composition; fungal and also bacterial components with biocontrol ability: Trichoderma hartianum Pseudomonas putida Bacillus subtilis Composition of inoculum is a critical issue for reducing the diseases: Trichoderma fungal biocontrol strains in TPB might act against Rhizoctonia infection, PGPR Pseudomonas bacteria in PPS might affect on Streptomyces diseases. However the annual variability might be highly affecting the plant-microbe interaction. Right time of application should also be re-considered. Further parameters, including pathogen abundance and soil-borne pathogens in soils need to be assessed on a long-term basis.
Thank you for your attention! Prof. Dr. Borbala Biro biro.borbala@gmail.com +36 3 7 663 Szent István University Faculty of Horticulture Dept. Soil Sciences and Water Management Orsolya Papp orsolya.papp@biokutatas.hu +36 3 74 Hungarian Research Institute of Organic Agriculture (ÖMKI)