The biocontrol effect of Paenibacillus jamilae QHZ11 on potato black scurf

Abstract:

[Background] Potato black scurf is a typical soil-borne disease caused by Rhizoctonia solani. At present, the bacterial resources for biological control of the disease are relatively limited, and the researches on the biological control mechanisms of corresponding strains are more lacking. [Objective] To clarify the biocontrol effect of QHZ11-an antagonistic bacteria of Rhizoctonia solani JT18, and reveal its partial biological control mechanisms on potato black scurf. [Methods] R. solani JT18 (CK), R. solani JT18 and ordinary organic fertilizer (OF), R. solani JT18 and amino acid organic fertilizer (AA+OF) and R. solani JT18 and QHZ11 biological organic fertilizer (BOF11) were inoculated respectively into the sterilized soil. Using real-time fluorescent quantitative PCR (RT-qPCR) method to study the quantity changes of R. solani JT18, and law of quantity's increase and declining between the antagonistic antibacterial QHZ11 and R. solani JT18 under the different treatments in the rhizosphere and different parts of the plant during the whole growth period of potato. At the same time, we compared the disease index of black scurf of different treatments and the corresponding control effects.[Results] The results of RT-qPCR showed that with the progress of potato growth, the quantity of R. solani JT18 in potato rhizosphere, roots and stolons under each treatment increased to the peak in the tuber expansion period, and then decreased. The quantity of R. solani JT18 in each part was:CK>OF>AA+OF>BOF11, rhizosphere>root>stolon. The quantity of antagonistic antimicrobial QHZ11 showed the same trend as R. solani JT18, but its peak appeared in the tuber formation period, and the colonization quantity of QHZ11 was significantly higher than R. solani JT18 in the same part of the same period, even two orders of magnitude higher. It showed that the existence of QHZ11 occupied certain nutrient resources and niches, which severely inhibited the growth and reproduction of R. solani JT18. The results of the disease showed that the disease index of CK was the highest, another three treatments were significantly lower than CK in which BOF11 had the least disease incidence. The results of biocontrol were just opposite, which were BOF11>AA+OF>OF. It showed that ordinary organic fertilizer, amino acid organic fertilizer and bio-organic fertilizer could control potato black scurf to varying degrees, among which bio-organic fertilizer had the most significant effect. [Conclusion] After QHZ11 is made into bio-organic fertilizer and applied to the soil, it can effectively inhibit the survival and reproduction of pathogen of black scurf by competing for nutrition and niches in the rhizosphere and different parts of potato plant, thereby achieving significant biocontrol effect. It is of great significance to the application and promotion of bio-organic fertilizer of QHZ11, and lays a foundation to further research the biological control mechanism of QHZ11.