Objectives Malus hupehensis Rehd. seedlings were used as test materials, and three kinds of microbiological fertilizers, namely, Penicillium cyclopium D12, Trichoderma harzianum and Penicillium oxalicum A1, were used to investigate their effects on root morphology and rhizosphere soil environment of Malus hupehensis Rehd. seedlings, which would provided theoretical basis for biological control of apple replant disease.
Methods In a pot experiment, Malus hupehensis Rehd. seedlings were used as test materials, and soils were collected from an apple orchard of Tanqingwan Village, Tai’an City of Shandong Province, where apple had been replanted for 31 years. Five treatments were set up: the replanted orchard soil (CK1), the carrier of fertilizer (CK2), Penicillium cyclopium D12 fertilizer (T1), Trichoderma harzianum fertilizer (T2) and Penicillium oxalicum A1 fertilizer (T3). The addition amount of biofertilizer were 1.00% of apple replanted orchard soil. After four months of growth, the seedlings were harvested, the root respiration rate, root system protects enzyme activity were measured, and the diversity of soil fungi were investigated.
Results Compared with CK1, T1, T2 and T3 significantly promoted the increase of root fresh weight and root respiration rate. After three kinds of biofertilizers were applied, the activity of root protective enzymes increased significantly, and the content of MDA decreased at the same time. Among them, T2 and T3 had better effects, and POD activities in T2 and T3 were increased by 120.06% and 108.73%, SOD activities were increased by 45.46%, 46.82%, and CAT activities were increased by 84.15% and 87.82%, respectively. At genus level, compared with CK1, the Fusarium relative abundance of T1, T2 and T3 decreased by 41.14%, 49.34% and 79.10%, respectively. The Penicillium and Trichoderma relative abundance of T1, T2 and T3 increased by 227.18%, 222.91%, 890.94%, and 76.55%, 462.71%, 213.56%, respectively. The Ace index, Chao index and Shan index increased significantly, while Simpson index decreased, indicating that the application of fertilizer could improve the diversity of soil fungi.
Conclusions The antioxidant enzymes was greatly improved, the root activity of Malus hupehensis Rehd. was promoted, and the abundance of Fusarium in soil was reduced by applying three kinds of fertilizers. Trichoderma harzianum and Penicillium oxalicum A1 have better application effect and could be used as effective measures to prevent and control apple replant disease.
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