Role of arbuscular mycorrhizal network in carbon and phosphorus transfer between plants

Intercropping with aerobic rice or arbuscular mycorrhizal fungi (AMF) colonization alleviated watermelon wilt disease, which is likely attributed to rice root exudates or AMF depressing watermelon wilt pathogen. However, it is unclear whether rice root exudates transfers to watermelon rhizosphere soil and whether AMF affects the transfer of rice root exudates to watermelon rhizosphere soil. A rhizobox experiment, with aerobic rice under 14 CO2, was conducted to investigate the effect of AMF colonization on carbon (C) transfer from rice to watermelon and on phosphorus (P) uptake by both watermelon and rice. The rhizobox was separated into labelling side (L side) and sampling side (S side) by inserting nylon mesh in the middle of the box. The L side was planted with aerobic rice, and the S side was aerobic rice (monocropping) or watermelon (intercropping). When 14 CO2 was added to rice canopy at the L side, 14 C activities of rice roots and rhizosphere soils in the L side were increased by intercropping with watermelon or AMF colonization. The 14 C was detected in roots and rhizosphere soils of rice and watermelon in the S side, but no differences were found among different treatments. 14 C activities in leaves were improved by AMF inoculation in the S side, regardless of rice or watermelon. Mycorrhizal colonization stimulated P absorption and translocation to rice in intercropping system. These findings suggest that AMF colonization could increase C transfer from rice to watermelon while intercropping with watermelon could promote AMF colonization and P uptake by rice.