甘肃省中部沿黄灌区轮作和连作马铃薯根际土壤真菌群落的结构性差异评估

甘肃省中部沿黄灌区是西北地区乃至全国重要的加工型马铃薯生产基地,然而因集约化种植带来的连作障碍问题已经严重影响到当地马铃薯种植业的可持续发展。采用大田试验与PCR-DGGE(Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis)技术相结合的方法,并通过真菌的18S r DNA序列分析,评估轮作(未连作)和连作条件下马铃薯根际土壤真菌群落在组成结构上的差异,以期为甘肃省中部沿黄灌区马铃薯连作的土壤障碍机理研究提供新证据。结果表明,同轮作相比,连作显著降低了马铃薯块茎产量和植株生物量,并且随着连作年限的延长,连作障碍也愈加严重。长期连作(6a)也导致马铃薯根冠比显著增加和植株收获指数的显著下降。在根际土壤真菌的种群数量和多样性上,连作和轮作间无显著差异,但在群落组成结构上差异明显。真菌18S r DNA测序分析进一步表明,马铃薯连作较轮作相比增加了Fusarium sp.和Fusarium solani以及Verticillium dahliae的种群或个体数量,而这些真菌是导致马铃薯土传病害的主要致病菌类型。根际土壤真菌群落组成结构的改变特别是与土传病害有关的致病菌滋生可能是导致当地马铃薯连作障碍的重要原因。

Evaluation on fungal community structure of rhizosphere soils of potato under rotation and continuous cropping systems in Yellow River Irrigation Areas of Middle Gansu Province

The yellow river irrigation areas of middle Gansu Province is one of the main processing potato growing regions in the Northwest China. Potato is often grown continuously by Gansu farmers and planting enterprises eager to maximize consecutive payoffs. This practice results in the severe decline in tuber yield and loss of tuber chemical qualities. Field studies was conducted to evaluate the differences in fungal community structure of rhizosphere soils of potato between rotation and continuous cropping systems in order to find the new evidence for the study on continuous cropping obstacle in Yellow River Irrigation Areas of Middle Gansu Province. In experimental site, three potato planting plots nearby each other were selected for this research, one is the rotation plot, namely, non continuous potato cropping, and two other plots had been continuously planted potato over 3 and 6 years, respectively. Rhizosphere soil samples were collected at 2011 potato harvest time, and then soil DNA was extracted. Subsequently, polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) was performed to analyse fungal community structure. The results revealed that continuous potato cropping significantly decreased tuber yield and plant biomass compared with potato rotation, and more seriously with the continuous potato cropping duration. In addition, continuous potato cropping over long-term significantly increased the ratio of root to shoot and also caused the decline in economic productivity of potato crop. There were no significant differences in fungal population quantity and diversity indices of rhizosphere soils between rotation and continuous cropping systems, whereas the obvious shift in community structure occurred. Sequence analysis of fungal 18S rDNA gene confirmed that continuous potato cropping increased population quantity or individual number of Fusarium sp. and Fusarium solani as well as Verticillium dahliae. Our results suggested that the decline of tuber yield and plant biomass in continuous potato cropping system might be associated with the change in fungal community structure of rhizosphere soils of potato, especially the increase in pathogen dynamic.