The root-knot nematode Meloidogyne incognita has a wide host range and it is one of the most economically important crop parasites worldwide. Biological control has been a good approach for reducing M. incognita infection, for which many nematophagous fungi are reportedly applicable. However, the controlling effects of Phanerochaete chrysosporium strain B-22 are still unclear. In the present study we characterized the parasitism of this strain on M. incognita eggs, second-stage juveniles (J2), and adult females. The highest corrected mortality was 71.9% at 3 × 10 8 colony forming units (CFU) mL-1 and the estimated median lethal concentration of the fungus was 0.96 × 10 8 CFU mL-1. Two days after treatment with Phanerochaete chrysosporium strain B-22 eggshells were dissolved. A strong lethal effect was noted against J2, as the fungal spores developed in their body walls, germinated, and the resulting hyphae crossed the juvenile cuticle to dissolve it, thereby causing shrinkage and deformation of the juvenile body wall. The spores and hyphae also attacked adult females, causing the shrinkage and dissolution of their bodies and leakage of contents after five days. Greenhouse experiments revealed that different concentrations of the fungal spores effectively controlled M. incognita. In the roots, the highest inhibition rate for adult females, juveniles, egg mass, and gall index was 84.61%, 78.91%, 84.25%, and 79.48%, respectively. The highest juvenile inhibition rate was 89.18% in the soil. Phanerochaete chrysosporium strain B-22 also improved tomato plant growth, therefore being safe for tomato plants while effectively parasitizing M. incognita. This strain is thus a promising biocontrol agent against M. incognita.

In order to clarify the main pathogens of tomato Fusarium wilt in Shanxi Province, China, morphological identification, elongation factor 1 alpha (EF-1α) sequence analysis, specific primer amplification and pathogenicity tests were applied to study the isolates which were recovered from diseased plants collected from 17 different districts of Shanxi Province. The results were as follows: 1) Through morphological and molecular identification, the following 7 species of Fusarium were identified: F. oxysporum, F. solani, F. verticillioides, F. subglutinans, F. chlamydosporum, F. sporotrichioides, and F. semitectum; 2) 56 isolates of F. oxysporum were identified using specific primer amplification, among which, 29, 5 and 6 isolates were respectively identified as F. oxysporum f. sp. lycopersici physiological race 1, race 2, and race 3; 3) pathogenicity test indicated the significant pathogenicity of F. oxysporum, F. solani, F. verticillioides, and F. subglutinans to tomato plant. Therefore, among these 4 species confirmed as pathogenic to tomato in Shanxi, the highest isolation rate (53.3%) corresponded to F. oxysporum. Three physiological species, race 1, race 2, and race 3 of F. oxysporum f. sp. lycopersici are detected in Shanxi, among which race 1 is the most widespread pathogen and is also considered as the predominant race.

27We characterized the parasitism by strain B-22 of Phanerochaete chrysosporium on 28 the eggs, second stage juveniles (J2), and adult females of the root-knot nematode 29 (Meloidogyne Incognita). Strain B-22 had a strong lethal effect against M. incognita J2. 30 The highest corrected mortality was 71.9% at 3  10 8 conidia mL -1 . The estimated LC 50 31 value was 0.96  10 8 conidia mL -1 . Strain B-22 parasitized M. incognita eggs 2 days after 32 treatment, causing the depression and dissolution of egg shells. The fungal spores 33 parasitized J2 by gathering in the body wall, germinating to develop hyphae, and crossing 34 the juvenile cuticle to dissolve it, thereby causing the shrinkage and deformation of the 35 juvenile body wall. The spores and hyphae also attacked adult females, causing the 36 shrinkage and dissolution of their bodies and leakage of contents in 5 days. Results of 37 greenhouse experiments showed that different concentrations of P. chrysosporium 38 effectively controlled different life stages of M. incognita and root knot symptoms in 39 tomato plants. Moreover, the control efficacy increased with increasing conidial 40 concentration; the best results were achieved with 3  10 8 cfu mL -1 . In the roots, the 41 highest inhibition rate was 84.61% for adult females, 78.91% for juveniles, 84.25% for the 42 egg mass, and 79.48% for the gall index. The highest juvenile inhibition rate was 89.18% 43 in the soil. Meanwhile, strain B-22 improved the plant growth. Thus, P. chrysosporium 44 strain B-22 is safe for tomato plants while effectively parasitizing M. incognita, making it a 45 promising biocontrol agent against M. incognita. 46 47 Keywords: Phanerochaete chrysosporium, Meloidogyne incognita, parasitism, 48 nematophagous fungus, pathogenicity, biocontrol agent49 3 50 Introduction 51 Plant-parasitic nematodes are very common in controlled-environment agriculture and 52 cause economic losses via reduction in greens quality and quantity. Global agricultural 53 losses caused by plant-parasitic nematodes have been estimated at more than $157 billion 54 [1]. Root-knot nematodes (Meloidogyne spp.), which comprise 98 species and parasitize 55 almost every species of vascular plants [2], are the most economically important 56 destructive obligate plant-parasitic nematodes. They occur globally, especially in tropical 57 and subtropical agricultural areas, and cause significant yield losses annually (at least $77 58 billion) to world crops [3]. Meloidogyne incognita is one of the most important species in 59 the genus Meloidogyne, and it causes dramatic yield losses in many cash crops (such as 60 tomato) in controlled-environment agriculture, which is the main approach to produce 61 vegetables and an important stepping stone to modern agriculture in China. The intensive 62 production, rich soil fertility, suitable soil temperature and moisture, and lack of effective 63 crop rotation in controlled-environment agriculture provide highly favorable conditions for 64 the growth and propagation of M. inc...

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