Control of Panama disease of banana by intercropping with Chinese chive (Allium tuberosum Rottler): cultivar differences.

Panama disease (Fusarium wilt disease) caused by Fusarium oxysporum f. sp. cubense race 4 (FOC) severely threatens banana (Musa spp.) production worldwide. Intercropping of banana with Allium plants has shown a potential to reduce Panama disease. In this study, six cultivars of Chinese chive (Allium tuberosum Rottler) were selected to compare their differences in antifungal activity and active compounds. Three cultivars Duokang Fujiu 11, Fujiuhuang 2, and Duokang Sijiqing with higher levels of antifungal compounds were further used for intercropping with banana in the pots and field to compare their effects on growth and disease incidence of banana.The six cultivars showed significant differences in antifungal activity against FOC mycelia growth in both leaf volatiles and aqueous leachates. The aqueous leachates displayed stronger antifungal activity than the volatiles. FJH cultivar showed the best inhibitory effect among all six cultivars. Contents of three main antifungal compounds dipropyl trisulfide (DPT), dimethyl trisulfide (DMT), and 2-methyl-2-pentenal (MP) in volatiles and aqueous leachates varied considerably among cultivars. Pot and field experiments showed that intercropping with three selected Chinese chive cultivars significantly improved banana vegetative growth, increased photosynthetic characteristics and yield but decreased disease incidence of Panama disease.Our results indicate that intercropping with Chinese chive shows potential to reduce banana Panama disease and selection of appropriate cultivars is vital for effective disease control.

Aboveground herbivory does not affect mycorrhiza-dependent nitrogen acquisition from soil but inhibits mycorrhizal network-mediated nitrogen interplant transfer in maize.

Arbuscular mycorrhizal fungi (AMF) are considered biofertilizers for sustainable agriculture due to their ability to facilitate plant uptake of important mineral elements, such as nitrogen (N). However, plant mycorrhiza-dependent N uptake and interplant transfer may be highly context-dependent, and whether it is affected by aboveground herbivory remains largely unknown. Here, we used 15N labeling and tracking to examine the effect of aboveground insect herbivory by Spodoptera frugiperda on mycorrhiza-dependent N uptake in maize (Zea mays L.). To minimize consumption differences and 15N loss due to insect chewing, insect herbivory was simulated by mechanical wounding and oral secretion of S. frugiperda larvae. Inoculation with Rhizophagus irregularis (Rir) significantly improved maize growth, and N/P uptake. The 15N labeling experiment showed that maize plants absorbed N from soils via the extraradical mycelium of mycorrhizal fungi and from neighboring plants transferred by common mycorrhizal networks (CMNs). Simulated aboveground leaf herbivory did not affect mycorrhiza-mediated N acquisition from soil. However, CMN-mediated N transfer from neighboring plants was blocked by leaf simulated herbivory. Our findings suggest that aboveground herbivory inhibits CMN-mediated N transfer between plants but does not affect N acquisition from soil solutions via extraradical mycorrhizal mycelium.