Effects of Common Mycorrhizal Networks and Arbuscular Mycorrhizal Fungi on Ascochyta Blight in Chickpea

Cicer arietinum L. (chickpea) is susceptible to Ascochyta blight (AB). Arbuscular mycorrhizal fungi (AMF) are symbiotic root colonizing fungi that exchange soil nutrients for photosynthetic carbon. AMF form common mycorrhizal networks (CMNs), connecting plant roots and transferring nutrients. CMNs are also hypothesized to transfer defense signals. Mycorrhizal induced resistance (MIR) can reduce plant disease severity. Intercropping chickpea with flax can reduce AB severity by incompletely understood mechanisms, potentially including CMN connection and defense signaling. Greenhouse experiments were conducted to test the hypotheses that: (a) chickpea permitted to form a CMN with a flax plant will have reduced AB severity relative to plant pairs where CMN formation was prevented, or where chickpea was paired with another chickpea plant; (b) a donor chickpea (inoculated with A. rabiei first) will reduce AB severity in a receiver chickpea (inoculated with A. rabiei second) due to connectivity with the CMN; and (c) AMF‐inoculated chickpea will have reduced AB severity due to MIR, relative to non‐AMF inoculated chickpea. Chickpea allowed to connect to another plant via a CMN had less severe AB, whether connected to another chickpea or to a flax plant. AB‐inoculation of a donor chickpea did not significantly decrease disease in the receiver plant. MIR significantly reduced AB severity in chickpea in one of three experiments. Therefore, connectivity to the CMN can lower AB severity in chickpea, by mechanism(s) other than defense priming, but is unlikely to contribute to chickpea–flax intercropping‐associated AB reductions.