拮抗细菌菌株Pseudomonas fluorescens 7-14在水稻植株上的时间、空间定殖型

Spatial-temporal colonization patterns of Pseudomonas fluorescens strain 7-14 on rice plants

Pseudomonasfluorescens 7 14 (Pf 7 14 )是一株对水稻纹枯病、稻瘟病和恶苗病有拮抗作用的细菌菌株。在温室条件下 ,在水稻孕穗后期喷雾浓度为 1× 10 10 cfu/mL的菌株Pf7 14悬浮液 ,采用定期取样 ,用稀释平板法回收细菌 ,并通过图形测试和Shapiro Wilk正态测试 ,测定了该菌株在水稻剑叶和茎基部的时间、空间定殖型。结果表明 ,菌株Pf 7 14在稻株上的定殖型随着时间的变化而改变。从定殖的空间上看 ,无论是在剑叶还是在茎基部 ,其定殖型可划分为 3种类型或 3个阶段 ,从最初的正态分布、之后的对数分布 ,发展到后期的不规则分布。对每一种分布型来说 ,菌株Pf 7 14在稻茎基部持续的时间比其在稻剑叶上长。在剑叶上 ,这 3种分布型持续的时间分别是 2h、7d和 10d,而在茎基部分别是 1、2 4d和大于 11d(至收获期 )。从定殖的时间和数量关系上看 ,在剑叶上 ,菌株Pf7 14的平均群体在 2 4h内下降了 90 %以上 ,在 7d内下降了 99% ,在 19d下降到检测不到的水平。而在稻茎基部 ,在 2 4h内下降小于 30 % ,在 7d内下降了大约 6 0 % ,在 35d内 ,部分样品中仍能检测到其群体。这些结果表明菌株Pf 7 14在茎基部比在叶片上更稳定 ,定殖的时间更长 ,这也很可能表明叶部病害 (如稻瘟病 )的生物防治将比茎部病害 (如纹枯病 )

Pseudomonas fluorescens strain Pf 7-14, a potential biocontrol agent, suppresses rice sheath blight, rice blast and bakanae. The spatial-temporal colonization patterns of this strain on both rice flag leaves and rice stems under greenhouse conditions were respectively determined in International Rice Research Institute,Philippines by spraying 1×10 10 cfu/mL bacterial suspension of Pf 7-14 at late booting stage, periodical sampling, and recovering the bacteria through diluting-plate method as well as graphic test and the Shapiro-Wilk test for normality of the data. The colonization patterns of the population of Pf 7-14 (natural nalidixic acid-resistant strain) were dynamically changeable over time. Whether was on flag leaves or stems, the colonization of the strain Pf 7-14 could be divided into 3 kinds of distribution patterns, from initial normal distribution, to lognormal distribution, and finally to irregular distribution. However, the duration of each distribution pattern on rice stems was longer than that on rice flag leaves. On flag leaves, the population declined more than 90% within 24 h after introduction, more than 99% on the 7th day, and was undetectable on the 19th day after its application. On rice stems, the population declined less than 30% within 24 h, about 60% on the 7th day, and was still detectable on some of the samples on the 35th day (harvest period) after its application. The results revealed that the population of strain Pf7-14 was more stable and survived longer on rice stems than on leaves, and also suggested that biocontrol of leaf diseases, for example, rice blast, was more difficult than that of sheath diseases.