Colonization on the Peanuts of Two Plant-growth Promoting Rhizobacteria Strains and Effects on the Bacterial Community Structure of Rhizosphere

doi:10.13560/j.cnki.biotech.bull.1985.2021-1577

Abstract

Abstract:

This work aims to investigate the growth-promoting mechanism of two plant growth-promoting rhizobacteria（PGPR）strains,Tsukamurella tyrosinosolvens P9 and Burkholderia pyrrocinia P10 on peanut. The two strains were labeled with GFP and rifampicin,respectively,and colonization dynamics of 2 strains in peanut tissues were studied,combined with scanning electron microscopy. Bacterial diversity of rhizosphere soil inoculated with 2 strains was analyzed by 16S rRNA whole-length sequencing. It showed that rifampicin-labeled strains P9 and P10 had good genetic stability,and their growth and growth-promoting characteristics were consistent with original strains,respectively. Two GFP-labeled strains colonized in the root tip and meristematic region of peanut. Rifampicin-labeled strains were stabilized in the roots and stems of peanut plants,and the colonization number remained 10⁴ CFU/g after 30 d of inoculation. In addition,the bacterial communities in inoculation groups of P9 and P10 and mixed strains were more similar than those in the un-inoculated control group. In three inoculation groups,the relative abundance of Flavihumibacter and unidentified_Rhizobiaceae increased significantly,and that of Bacillus and Streptomyces increased in different degrees compared with CK,while the abundance of Lysobacter,Achromobacter and Pseudoxanthomonas decreased. The two PGPR strains could not only directly colonize in peanut tissues,but also indirectly affect soil bacterial community structure to promote the growth of peanut. The inoculation of mixed strains had better growth promotion effect on peanut. The results clearly elucidate the growth-promoting mechanism of the two PGPR strains,and provide scientific basis for the further application of the strains.

Key words: Tsukamurella tyrosinosolvens, Burkholderia pyrrocinia, peanut, colonization, bacterial community structure

LI Ying, LONG Chang-mei, JIANG Biao, HAN Li-zhen. Colonization on the Peanuts of Two Plant-growth Promoting Rhizobacteria Strains and Effects on the Bacterial Community Structure of Rhizosphere[J]. Biotechnology Bulletin, 2022, 38(9): 237-247.

Figures/Tables 10

Fig.1 PCR verification of positive transformants of GFP-labeled strains M：1 000 bp marker;1：positive control;2 and 4：original strain of P9 and P10,respectively;3 and 5：positive transformants of GFP-labeled P9 and P10,respectively

Fig.2 Distribution of two GFP-labeled PGPR strains on the root tips of peanut A：Root tip of CK;B and C：meristem region of root tip of CK;D：root tip of P9 treated group;E and F：meristem region of P9 treated group;G：root tip of P10 treated group;H and I：meristem region of P10 treated group. All are the images of microscope objectives 40,except that B,E and H are of objectives 20

Fig.3 Colony morphology and cell morphology of two rifampicin-labeled PGPR strains A and B are the colonies of P9r and P10r on rifampicin LB plate respectively;C and D are the cell morphologies of P9r and P10r under scanning electron microscopy,respectively

Fig. 4 Growth curves of two PGPR strains and their rifampicin-labeled strains P9 and P10 are original strains,P9r and P10r are rifampicin-labeled strains,the same below

Table 1 Growth-promoting characteristics of two PGPR strains and their rifampicin-labeled strains

菌株 Strain	可溶磷含量 Soluble phorsphorus content/（µg·mL^-1）	IAA含量 IAA content /（mg·L^-1）	ACC脱氨酶活性 ACC deaminase activity/（μmol·（h·mg）^-1）	铁载体相对含量 Siderophore relative content/%
P9	307.84±10.81a	38.72±0.52a	1.00±0.09a	83.40±0.40a
P9r	297.28±1.40a	36.35±1.46a	0.99±0.02a	83.20±0.50a
P10	74.09±3.71b	44.91±1.3b	26.31±1.53b	83.80±1.60a
P10r	67.26±0.53b	40.31±1.13bc	25.96±1.69b	81.90±2.10a

Fig.5 Colonization dynamics of two rifampicin-labeled PGPR strains in peanut soils,roots and stems

Fig.6 Colonizaiton of two rifampicin-labeled strains on root and stem surface observed by scanning electron microscope A：Un-inoculated root of peanut;B：P9r treated root;C：P10r treated root;D：P9r+P10r treated root;E：uninoculated stems;F：P9r treated stems;G：P10r treated stems;and H：P9r+P10r treated stems

Table 2 Effects of two rifampicin-labeled and their original PGPR strains on the growth of peanuts

处理 Treatment	鲜重 Fresh weight/g	株高 Plant height /cm	总根长 Total root length /cm	根重 Root weight /g	叶绿素含量 Cholorphyll content /（mg.g^-1FW）
CK	2.91±0.14a	8.92±0.37a	7.48±0.37a	0.524±0.05a	3.72±0.20a
P9r	3.23±0.28ab	11.68±0.22b	11.78±1.23b	0.580±0.06a	4.39±0.39a
P10r	3.03±0.09b	12.53±0.31bc	10.88±0.18b	0.524±0.05a	4.35±0.31a
P9r+P10r	4.20±0.32c	14.28±0.54d	12.08±0.45bc	0.718±0.06bc	4.37±0.26a
P9	3.84±0.16bc	13.18±0.30cd	11.37±0.50b	0.624±0.03ab	4.65±0.14a
P10	3.79±0.27bc	14.23±0.22d	13.83±0.54c	0.739±0.02bc	4.38±0.39a
P9+P10	4.92±0.23d	16.78±0.61e	12.60±0.27bc	0.843±0.01c	4.62±0.36a

Fig.7 Multi-samples Shannon curves and principal component analysis（PCA）of bacterial communities in peanut rhizosphere soil Left：Shannon curves. Right：PCA analysis. A,B,C,D represents CK,P9-inoculated group,P10-inoculated group,P9+P10 inoculated group,respectively

Fig. 8 Relative abundances of bacteria communities at phy-lum and genus level in rhizosphere soils of different treated peanuts A：Phylum level. B：Genus level

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