Effects of intercropping watermelon with rain fed rice on Fusarium Wilt and the microflora in the rhizosphere soil

Chinese. 探讨西瓜与旱作水稻间作减缓西瓜连作障碍的可行性，并从微生物多样性与连作障碍关系角度阐释该方法的作用机理。盆栽方法研究西瓜与旱作水稻间作改善西瓜连作障碍的效果，传统微生物计数及磷脂脂肪酸（PLFA）法研究西瓜根际土壤微生物区系。西瓜连作土壤上单作西瓜其枯萎病发病率为 66.7%，死亡率为44.4%，与旱作水稻间作后西瓜生长正常。西瓜定植30 d后，间作处理西瓜根际的尖孢镰刀菌数量显著低于单作；50 d后，间作西瓜根际土中的真菌数量显著低于单作，而细菌、放线菌及总微生物数量均显著高于单作。磷脂脂肪酸（PLFA）法分析土壤微生物多样性发现，单作处理的西瓜根际土壤中真菌数量较多，细菌数量较少，而且主要是革兰氏阳性菌，而间作西瓜根际则含有较多的革兰氏阳性菌、革兰氏阴性菌和放线菌。间作处理西瓜体内的丙二醛（MDA）含量及保护性酶类如根系及叶片中的过氧化氢酶（CAT）、过氧化物酶（POD）、多酚氧化酶（PPO）和根系中的苯丙氨酸解氨酶（PAL）活性均显著低于单作西瓜。西瓜与旱作水稻间作条件下西瓜根际尖孢镰刀菌数量显著降低，根际微生物区系向细菌与放线菌占主导的趋势发展，有效防止了西瓜枯萎病的发生，改善了西瓜连作障碍。

English. Feasibility alleviating wilt disease occurred in continuously cropping soil with an intercropping system of rain fed rice together with watermelon crops were tested, focusing on the microflora in rhizosphere soil of watermelon. A pot experiment was conducted to investigate the control of watermelon Fusarium wilt by intercropping with rain fed rice. Both phospholipid fatty acids (PLFA) and traditional enumeration methods were used to determine microflora in rhizosphere soil of watermelon. Results showed that 66.7% of watermelon were infected with wilt disease and 44.4% died after 40 days of transplanting in monocropping system. By contrast, watermelon grew normally in intercropping system. Fusarium oxysporum density decreased significantly in intercropping system compared to those in monocropping treatment after 30 days after transplanted. Bacteria, actinomyces and total microorganism densities significantly increased and fungus density remarkably decreased compared to those in monocropping system after 50 days after transplanted. Changes of microbiodiversity were also observed in watermelon rhizosphere soil in intercropping system by phospholipid fatty acids (PLFA) method. There were more Gram-positive bacteria, Gram-negative bacteria and actinomyces and less fungus in intercropping system than those in monocropping treatment. Lower malondialdehyd (MDA) content and catalases (CAT), peroxidases (POD), polyphenoloxides (PPO) activities in roots and leaves and phenylalantine ammonia lyases (PAL) activity in leaves of watermelon were observed in intercropping system compared to those in monocropping system. Watermelon wilt disease was significantly alleviated in intercropping system by restraining pathogen (Fusarium oxysporum) growth and regulating the microflora in rhizosphere soil of watermelon.