ABSTRACT

The chitin-hydrolyzed product LMC60 contains low-molecular-weight chitin (LMwC) with an average molecular weight of approximately 3,000 and sodium chloride formed by neutralization process. LMwC and a soil amendment with LMC60 (SLMC60) showed suppressive effects on plant diseases caused by pathogenic microbes. The spectrum of plant diseases against which SLMC60 was effective is however distinct from that of chitin, implying the unique effects of SLMC60 on plants and soil microorganisms. As a part of the study to elucidate the cause of the spectrum difference between chitin and SLMC60, we report here not only the degradation profile but also the antifungal property and microbial community structure in LMC60-added soil, in comparison with those in chitin-added soil and soil without supplement. Both LMC60-added and chitin-added soils inhibited the growth of a pathogenic Fusarium oxysporum strain, compared with the soil without supplement. The declining trend in the amount of LMC60 and chitin, and the patterns of ammonium accumulation, indicated equivalent degradation profiles of LMC60 and chitin at 25°C. The number of culturable bacteria increased in soil with LMC60 and chitin, but the number of culturable fungi and content of ergosterol, which is specific to fungal cells, increased only in the soil with LMC60. The effects of LMC60 and chitin on bacterial and fungal community structures were clearly distinguishable, as follows: The relative abundance of three bacterial families (Bacillaceae, Paenibacillaceae, and Alcaligenaceae) increased significantly only with LMC60. LMC60 increased the relative abundance of the family Promicrosporaceae earlier than chitin. In terms of fungi, Fusarium increased in the presence of LMC60 and chitin, the Mortierella population expanded considerably only with chitin, and Colletotrichum and Malbranchea increased only with LMC60. These effects of LMC60 on soil microorganisms which are distinct from those of chitin might suggest its spectrum of plant disease suppression.

摘要

几丁质水解产物 LMC60 含有平均分子量约为 3,000 的低分子量几丁质 (LMwC) 和通过中和过程形成的氯化钠。LMwC 和含有 LMC60 的土壤改良剂 (SLMC60) 对病原微生物引起的植物病害具有抑制作用。然而，SLMC60 有效对抗的植物病害谱与几丁质不同，这意味着 SLMC60 对植物和土壤微生物具有独特的影响。作为阐明几丁质和 SLMC60 之间光谱差异原因的研究的一部分，我们在此不仅报告了 LMC60 添加的土壤中的降解曲线，还报告了抗真菌特性和微生物群落结构，与添加几丁质的土壤相比土不补土。Fusarium oxysporum菌株，与未补充的土壤相比。LMC60 和几丁质含量的下降趋势以及铵积累的模式表明 LMC60 和几丁质在 25°C 下的降解曲线相当。LMC60 和几丁质在土壤中可培养细菌的数量增加，但可培养真菌的数量和真菌细胞特异性麦角甾醇的含量仅在 LMC60 的土壤中增加。LMC60 和几丁质对细菌和真菌群落结构的影响是清晰可辨的，如下所示：三个细菌科（芽孢杆菌科、类芽孢杆菌科和 Alcaligenaceae）的相对丰度仅随着 LMC60 显着增加。LMC60 比几丁质更早地增加了 Promicrosporaceae 家族的相对丰度。在真菌方面，镰刀菌在 LMC60 和几丁质的存在下增加，被孢霉种群仅在几丁质的情况下显着增加，而炭疽菌和Malbranchea仅在 LMC60 的情况下增加。LMC60 对土壤微生物的这些不同于几丁质的影响可能表明其对植物病害的抑制谱。