The Interaction Of Host Plants And Serratia Plymuthica A21-4 Colonization Ability

This study was to analyze the Colonization density of S. plymuthica A21-4 in the deffrent crop species, variety, growth stage and root exudates, also to research the impact of S. plymuthica A21-4 to pepper growth, root activity, plant resistance related enzymes activity and rhizosphere microbial populations, to clear the relationship between host plants and colonization of S. plymuthica A21-4, to make a preliminary analysis of its mechanism of rhizosphere colonization and inducible resistance, to provide students with theoretical basis of improve and stabilize the control effect of A21-4.The results of the impact of host plants on the colonization density of S. Plymuthica A21-4 reveals that: A21-4 strains was have a capacity of rhizosphere colonization, in pepper, tomato, cucumber, watermelon, cabbage and cauliflower and other crops , its colonization density can be above 4×103cfu·cm^-1 and 2×10⁴cfu·g^-1 both in the double filter method and pot test, the colonization density of S. Plymuthica A21-4 have certain difference, in cucumber and pepper roots the colonization density of S. Plymuthica A21-4 can reach 9×10⁴cfu·cm^-1 and 8×10⁴cfu·g^-1 both in the double filter method and pot test; there is no Significant difference in the colonization density of S. Plymuthica A21-4 in the different cucumber and pepper cultivars roots, indicating that plant cultivars have no effect on colonization density of S. Plymuthica A21-4. In the pepper seedling stage, the colonization density of S. Plymuthica A21-4 tends to decline with time in the rhizosphere soil, but on the 30th day of transplanting, the colonization density still can be more than 106cfu·g^-1, the colonization density remained stable in the pepper roots, on the 30th day of transplanting, the colonization density can reach 1.02×10⁶cfu·g^-1. In the soil of pepper rhizosphere, the colonization density of A21-4 was not significantly different no matter whether the pathogen exist or not, but in the pepper roots when pathogen exists, the colonization density of A21-4 was significantly higher than that absence of pathogen condition. in the whole growth period of the peper the colonization density of S. Plymuthica A21-4 show stability in the early stage and slow decline later; in the different growing stage with S. Plymuthica A21-4, the colonization density in the pepper rhizosphere is that colonization density is higher with late treatment, while the colonization density of the pepper roots is colonization density in the transplanting period with soaking pepper roots is higher than perfusion after transplanting period. Pepper root exudates can significantly enhance the rcolonization density of S. Plymuthica A21-4 in the pepper roots, In the simulation components of root exudates, organic acids is lactic acid, amino acids are leucine and glutamine gln, carbohydrate is lactose, inorganic salt is FeSO4, contain N materials are beef creams and NH4H2PO4, that can significantly improve the effect that the rcolonization density of S. Plymuthica A21-4 in the pepper roots is enhanced.the results of the impact of S. Plymuthica A21-4 on pepper growth and root micorecological is to reveal that: in pepper breeding period,A21-4 significantly enhanced the morphological index of pepper, fresh and dry weight, chlorophyll content and root activity, the chlorophyll content of the pepper treated with A21-4 was increased by 86.1%, and root activity of the pepper that treated with A21-4 was increased by 481.8%; in pepper maturity period, A21-4 significantly enhanced pepper plant height, stem diameter and branch segments and other fertility index. Through the treatment with A21-4, SOD, POD and PAL activity was significantly increased in the pepper roots and leaves, the peak of SOD, POD and PAL activity were increased by 44.7%, 64.2% and 77.0% respectively in the pepper roots, and the peak of SOD, POD and PAL activity were increased by 27.9%, 134.9% and 87.0% respectively in pepper leaves; while soaking pepper roots with A21-4 can enhance disease resistance of the leaves in spatial segregation and show the resistance to Phytophthora capsici in pepper leaves. There was no significant effect on the types and population of fungi, bacteria and actinomycetes in the pepper rhizosphere, so incoming A21-4 can maintain the stability of prpper root micorecological.