棉花连作对北疆土壤酶活性、致病菌及拮抗菌多样性的影响

本文通过测定土壤酶活性与微生物PCR-DGGE指纹图谱研究了北疆棉区5年棉花连作(CtN5)、10年棉花连作(CtN10)及15年棉花连作(CtN15)对土壤过氧化氢酶、蔗糖酶、芳基硫酸酯酶、脱氢酶和蛋白酶酶活性的影响,分析了土壤细菌、真菌、镰刀菌和枯草芽孢杆菌群落结构多样性对北疆棉田长期连作的响应。结果表明:过氧化氢酶、蔗糖酶、脱氢酶活性随棉花连作年限延长而下降。CtN15处理的过氧化氢酶、蔗糖酶和脱氢酶活性分别比CtN10处理下降15.0%、6.4%和12.0%,比CtN5处理下降16.8%、58.6%和49.5%(P0.05);芳基硫酸酯酶与蛋白酶活性随连作年限的增加呈先下降后升高的特点。土壤细菌、真菌多样性指数随连作年限的增加明显下降。CtN15的细菌条带数比CtN10下降7.41%,Ct N10比CtN5降低1.72%。CtN15真菌条带数和Shannon-Wiener多样性指数分别为78和3.22,比CtN5处理低17.02%和5.29%。土壤镰刀菌和枯草芽孢杆菌的条带数、多样性指数均表现为先下降后升高。CtN15枯草芽孢杆菌Shannon-Wiener和Simpson指数分别比CtN10处理高54.8%和14.5%。北疆长期连作棉田的土壤酶活性和土壤微生物群落多样性总体呈下降趋势,长期连作对棉田土壤生物性状有明显负面影响。

Response of soil enzyme activity and microbial community structure, diversity to continuous cotton cropping in northern Xinjiang

As a major cash crop, cotton has been widely cultivated for several decades in Xinjiang Uygur Autonomous Region (referred to as Xinjiang). Due to continuous cotton cropping over a long period, soil-borne diseases (e.g., Fusarium sp. and Verticillium dahlia) have worsened in cotton fields in recent years, resulting in substantial yield declines. The objective of this study was to determine the effects of long-term cultivation of cotton on soil biological activity, soil microbial community structure, microbial genetic diversity (e.g., total bacterial and total fungi) and specific soil microbe (e.g., fusarium and bacillus). Three cotton treatments continuous mono-cropping for 5 consecutive years (CtN5), for 10 consecutive years (CtN10) and for 15 consecutive years (CtN15)] were set up in an oasis farmland in northern Xinjiang. Then soil peroxidase, invertase, arylsulfatase, dehydrogenase, and protease activities were measured, while soil microbial community structure diversities of total bacteria, total fungi, fusarium soil-borne pathogenic bacteria and bacillus soil antagonistic bacteria were determined using PCR-DGGE fingerprint approach. There was a significantly decreasing tendency in soil catalase, invertase and dehydrogenase activities with increasing years of continuous cropping. For instance, compared with CtN10, CtN15 treatment decreased activities by 15.0% for catalase and by 6.4% for invertase. However, arylsulfatase and protease activities decreased from continuous cotton cropping of 5 years (CtN5) to 10 years (CtN10) followed by an increasing tendency from continuous cotton cropping of 10 years (CtN10) to 15 years (CtN15). The Shannon-Wiener and Simpson indices of soil total bacteria and total fungi declined markedly with increasing years of continuous cotton cropping. Compared with CtN10, the quantity of soil total bacteria gene band (DGGE fingerprint) decreased by 7.41% under CtN15. It decreased by 1.72% from CtN5 treatment to CtN10 treatment. The values of soil total fungal gene band and Shannon-Wiener diversity index were 78 and 3.22 under CtN15 treatment, suggesting respectively 17.02% and 5.29% decreases under CtN15 compared with CtN5. Compared with CtN10 treatment, the Shannon-Wiener and Simpson indices of soil bacillus community increased respectively by 54.8% and 14.5% under CtN15 treatment. Moreover, the amount of fusarium gene and bacillus gene bands as well as the related diversity indices decreased from CtN5 to CtN10 treatment, but then increased from CtN10 to CtN15. In conclusion therefore, soil enzyme activity and microbial community structure and diversity decreased with increasing years of continuous cotton cropping. Long-term, continuous cultivation of cotton had an adverse effect on soil biological characteristics in northern Xinjiang.