JIA-2019-11

2567 LIU Ying et al. Journal of Integrative Agriculture 2019, 18(11): 2561–2570 development of nematodes in AW2017 - treated plants was slightly delayed compared with that in PDB-treated control plants. The percentage of J4s and adult females in 5×AW2017 ((30.3±5.2)%) and 10×AW2017-treated plants ((40.8±5.4)%) was significantly lower than that in nontreated plants ((57.9±4.7)%), whereas a higher ratio of J3s was observed in 5×AW2017 ((69.7±6.3)%) and 10×AW2017- treated roots ((59.2±7.1)%) than in PDB control-treated roots ((42.1±5.8)%) (Fig. 5-C). These data suggest that drenching with A . welwitschiae not only decreases infection by M . graminicola but also delays nematode development inside roots. 4. Discussion Nematophagous fungi are potential alternatives to chemical nematicides in controlling plant parasitic nematodes that would avoid the deleterious effects of chemicals on humans and the environment (Kumar and Singh 2006; Khan et al . 2012; Saikia et al . 2013; Singh et al . 2013). Based on the present research, it is evident that the application of A . welwitschiae significantly decreases the attractiveness of A . welwitschiae -treated rice roots to M . graminicola and significantly reduces nematode penetration of rice roots. After nematodes penetrated A . welwitschiae -treated rice roots, their development in the rice roots was delayed. The reduction in penetration achieved with A . welwitschiae confirms previous works showing that biocontrol fungi are promising candidates for nematode control (Padgham and Sikora 2007; Le et al . 2009, 2016; Singh et al . 2013). The effect of A . welwitschiae on the reduction in nematode penetration was higher than that of the rhizosphere fungi Trichoderma spp. (Le et al . 2009) but lower than that of the endophyte F . moniliforme (Le et al . 2016) and the nematode-trapping fungus A . oligospora (Singh et al . 2012). In addition, the attraction of M . graminicola juveniles to the A . welwitschiae -treated rice roots was lower than that to the roots of control plants, which is similar to the attraction effect of endophytic F . moniliforme on M . graminicola (Le et al . 2016), suggesting that the impairment of host-finding ability is an important means for reducing nematode invasion (Padgham and Sikora 2007). In light of these observations, this is the first proposed biological method to control M . graminicola in China, and this research highlights a promising strategy for the biological control of RKNs in rice planting systems. Additional research is needed to better understand the interaction mechanism of this biocontrol system. The Fig. 5 Infection and development of Meloidogyne graminicola inside rice roots at 14 d post inoculation (dpi). A, nematodes in PDB and different Aspergillus welwitschiae suspension-treated plants were counted and photographed at 14 dpi. B, root galls in PDB and different A. welwitschiae suspension-treated plants were counted at 14 dpi. C, the ratio of nematodes in rice roots at different developmental stages was calculated at 14 dpi. Each plant was inoculated with ±300 second-stage juveniles (J2s). The experiment was performed three times, with eight replicates each. Values with the same letters above the bar are not signi cantly different at the P ≤0.05 level according to Duncan’s multiple range test. a c b 0 50 100 150 200 250 A B C PDB 5×AW2017 10×AW2017 Number of nematodes per plant Different suspension a b b 0 10 20 30 40 50 PDB 5×AW2017 10×AW2017 Number of root galls per plant Different suspensions c a b b d c 0 50 100 PDB 5×AW2017 10×AW2017 PDB 5×AW2017 10×AW2017 J3 J4 and female Percentage of nematodes (%) Different developmental stages J4 PDB 5×AW2017 10×AW2017 J4 J3 J3 Female Female Female