两株PGPR对豇豆苗期生长及土著细菌群落的影响

以扬豇40为材料,研究了植物根际促生菌Pseudomonas chlororaphis RA6和Bacillus pumilus WP8对豇豆种子出苗及幼苗生长的作用,评价浸种及拌土处理的差异,揭示一段时间内,两株植物根际促生菌(PGPR)在土壤中的行为特征及其对土著细菌群落结构的影响。结果表明:PGPR对豇豆的促生作用因接种方式、接种量的不同而不同。WP8、RA6浸种处理的出苗率分别比对照提高14.29%和9.52%(P<0.05);15 d时的株高分别比对照提高14.39%和10.40%(P<0.05);茎叶干物重分别比对照增加19.69%和17.71%(P<0.05)。WP8、RA6低剂量拌土处理(104cfu·g-1soil,以下简作"低拌处理")各指标与对照相比,均无显著差异(P>0.05)。WP8、RA6中剂量拌土处理(106cfu·g-1soil,以下简作"中拌处理")出苗率和株高均比对照提高,但未达显著差异(P>0.05);茎叶干物重分别比对照增加12.71%和18.59%(P<0.05)。WP8、RA6高剂量拌土处理(108cfu·g-1soil,以下简作"高拌处理")出苗率分别比对照提高9.52%和14.29%(P<0.05);15 d时的株高分别比对照提高6.37%和7.64%(P<0.05);茎叶干物重分别比对照增加27.37%和20.43%(P<0.05)。DGGE指纹图谱分析结果显示:各处理在15 d和45 d时,除WP8浸种处理外,其余土壤微生物群落多样性和对照均已发生明显变化,随时间推延,RA6菌株在土壤中优势地位更趋明显,表现在45 d时仍可明显检测到;WP8在土壤中存活时间不长,但拌土处理改变了土著细菌的群落结构。推测WP8的促生作用很可能与土著微生物群落的变化有关。

Effects of Two Plant Growth-promoting Rhizobacteria ( PGPR ) on Yardlong Bean Early Seedlings Growth and Indigenous Soil Bacterial Community

The object of the present paper is to explore the effect of two PGPRs,Pseudomonas chlororaphis RA6 and Bacillus pumilus WP8,on yardlong bean growth,and the difference of two methods of application,seeds soaking and soil drenching,as well as PGPR survival and its impact on the indigenous bacterial community.The results showed that PGPR effects of isolated strains on yardlong bean growth depended on inoculation methods and inoculation size.By seed soaking with WP8 and RA6,germination rate of yardlong bean seeds was increased by 14.29% and 9.52% respectively(P<0.05)from the contro(l CK);plant height at 15 days after germination was increased by 14.39% and 10.40%(P<0.05)respectively;above-ground dry weight was increased by 19.69% and 17.71%(P<0.05)respectively.By soil drenching with WP8 and RA6,plant height and above-ground dry weight were not significantly different from those of control when inoculation rate was low(104 cfu.g-1 soil).However when inoculation rate was increased to 108 cfu.g-1 soil,seed germination rate was increased by 9.52% and 14.29% respectively(P<0.05);plant height at 15 days after germination was increased by 6.37% and 7.64%(P<0.05);above-ground dry weight was increased by 27.37% and 20.43%(P<0.05).These data suggested that the PGPR strains were potential bio-agents promoting yardlong bean growth.Denaturing gradient gel electrophoresis(DGGE)analysis based on 16S rRNA sequences indicated that microbial communities in PGPR treated soils were obviously different from those in control soil.Strain RA6 specific band became intensified as the time passed.However,strain WP8 specific band became weak as time passed.