Abstract:

Root rot and root-knot nematode diseases seriously cause damages to vegetable production. It was reported that Purpureocillium lilacinum and Trichoderma harzianum presented potentials to control the individual root rot or root-knot nematode disease. In order to screen P. lilacinum and T. harzianum strains for simultaneously controlling these two diseases,25 rhizospheric soil samples of Solanaceae and Cucurbitaceae vegetables were collected from 5 provinces on the north of Beijing,and 699 strains of fungal strains were isolated. The 89 strains were screened out to be antagonistic to the pathogenic strain Fusarium oxysporum,and their taxonomy were determined by sequencing the products amplified with ITS1/ITS4 prime pairs. Three P. lilacinum（2018-31,2018-32 and 2019-79）and two T. harzianum（2018-44 and 2018-54）strains were identified,and their safety to the host was evaluated by soaking the cucumber seedlings（Zhongnong 18）in the fermentation suspension. The results showed that one P. lilacinum（2018-32）and two T. harzianum（2018-44 and 2018-54）were proved to be non-pathogenic to the cucumber seedlings. Pot experiments were conducted to further investigate their efficiency for controlling the cucumber root rot and root-knot nematode disease,and the results showed that the control efficiency of P. lilacinum（2018-32）and T. harzianum（2018-44）strain on the root rot disease was 81.19% and 73.08%,respectively. While the control efficiency of P. lilacinum（2018-32）and T. harzianum（2018-44）strain on the root-knot nematode disease was 64.06% and 50.54%,respectively. All were better than the commercial agent of the same type. Our results revealed that the screened P. lilacinum（2018-32）and T. harzianum（2018-44）strain presented promising efficiency for simultaneously controlling cucumber root rot and root-knot nematode diseases.

Key words: vegetable rhizospheric soil, root rot disease, root-knot nematode disease, biocontrol fungi, Purpureocillium lilacinum, Trichoderma harzianum