| Potato black scurf infected by Rhizoctonia solani(R.solani)is the main soil-borne disease that seriously affects the healthy development of the potato industry in Gansu Province.However,as the safest and most effective green control method,biological control is limited by factors such as limite of biocontrol bacteria resources and lack of researches on biocontrol mechanisms.This research took Paenibacillus jamilae QHZ11,which had a significant inhibitory effect on R.solani and was selected by the research group in the early stage,as the research object,used pot experiments(four treatments: T1: sick soil(added R.solani into sterilized soil);T2:sick soil+ ordinary organic fertilizer;T3: sick soil+amino acid organic fertilizer;T4:sick soil+QHZ11 biological organic fertilizer)and combined with q PCR to study the quantity changes and law of quantity’s increase and declining between the antagonistic antibacterial QHZ11 and pathogen R.solani in potato different periods,and study the influences of QHZ11 bio-organic fertilizer on potato plant defense gene expression,defensive enzyme activity,biocontrol effect against potato scurf disease and growth promotion effect on potato to reveal the biocontrol mechanism of the antagonistic antibacterial QHZ11 against the potato black scurf,and clarify the biocontrol effects of QHZ11 bio-organic fertilizer on potato black scurf and growth-promoting effect on potatoes.The main results are as follows:1.The colonization of QHZ11 in the potato rhizosphere and different parts of the plant significantly inhibited the growth of R.solani(1)As the growth period was progressed,the quantity of QHZ11 colonization in the potato rhizosphere,roots and stolons all increased to the peak during tuber formation,and then declined.The lowest quantity appeared in the bud stage,which was 2 orders of magnitude lower than tuber formation period.(2)Compared with the control(T1),whether in the rhizosphere or in different parts of the plant,the quantity of R.solani in the T2-T4 treatments was significantly lower than that of the control at each stage,especially the T4 bio-organic fertilizer treatment was the most significan,which was 2 orders of magnitude lower than the CK;in the 4 treatments,the quantity of R.solani first increased to the peak in tuber expansion stage,and then declined,indicating that the add of QHZ11 significantly inhibited the growth of R.solani.(3)During the whole growth period,the quantity of QHZ11 in rhizosphere,roots and stolons were significantly higher than that of R.solani.As the growth period was progressed,the difference between the two gradually increased until the tuber formation period reached the maximum,which was 2 orders of magnitude.Afterwards,the difference began to shrink,indicating that in the competition with R.solani,QHZ11 always dominated with quantitative advantages,thus exerting a group effect and significantly inhibiting the growth of pathogenic bacteria.2.QHZ11 can induce systemic resistance of potato plant(1)QHZ11 could induce expression of key enzyme genes in the synthesis pathway of JA,SA and ET in potato different growth periods.Among them,the key enzyme genes po AOS and po LOX of JA synthesis and the key enzyme gene po PAL of SA synthesis reached the peak during the tuber formation period;and the peak of expression of the key enzyme gene po ACS of ET synthesis was the tuber expansion period.It shows that JA,SA and ET are important signal molecules for potato resisting against black scurf,and QHZ11 can induce the synthesis of JA,SA and ET,in turn,the resistance of potato plants against black scurf is induced.(2)QHZ11 could induce changes of the activities of SOD,POD and CAT in potato stem and leaf tissue,and the effect on each enzyme was roughly the same on the stem and leaves.Among them,the induction to SOD activity was mainly in the seedling stage,and the activity of leaf POD could be induced in all stages,the activity of CAT was not affected in the early stage of growth,but it would reduce the activity of CAT in stems and leaves in the later stage,indicating that the antagonistic QHZ11 can induce systemic resistance of plant by increasing the defensive enzyme activity of the plant.3.QHZ11 bio-organic fertilizer has a significant biocontrol effect on potato black scurf and can effectively promote the growth of potato plants,improve root morphology and increase tuber yield(1)The disease index of T1 was the highest,and the T4 was the lowest;The control effect was opposite,which was T4>T3>T2 treatment.It shows that ordinary organic fertilizers,amino acid organic fertilizers and bio-organic fertilizers can all prevent and control potato black scurf to varying degrees,among them,bio-organic fertilizer has the most significant effect.(2)Compared with the control(T1),T4,T3 and T2 treatments could all promote the growth of the above-ground parts of potatoes,among which the change in plant height was most obvious;increasing the above-ground and underground biomass,the change of above-ground dry weight was the most obvious;promoting the growth of potato roots and improving its morphology,and the change of the root surface area was the most prominent;they could also significantly increase the tubers per plant and the weight of tubers.Among them,the effect of the biological organic fertilizer was the most significant.The colonization of Paenibacillus jamilae QHZ11 in the potato rhizosphere,roots and stolons can significantly inhibit the growth of pathogen of scurf disease,and QHZ11 can induce systemic resistance of potato plant against black scurf disease.Meanwhile,QHZ11 bio-organic fertilizer has a significant biocontrol effect on potato black scurf disease and can effectively promote the growth of potato plants,improve root morphology and increase tuber yield.This research provides a strong support for further clarifying the biocontrol mechanism of QHZ11 against potato black scurf,and is of great significance to the field application and popularization of QHZ11bio-organic fertilizer. |
PDF Full Text Request