Prospecting intercropping between subterranean clover and grapevine as potential strategy for improving grapevine performance

Intercropping is an agricultural practice commonly used to improve plant nutrition. In this study, we prospected the interaction between root exudates of subterranean clover (Trifolium subterraneum L.) and grapevine (Vitis vinifera L.). This experiment was focused on the detection of organic acids, amino acids, and flavonoids in root exudates released by grapevine and subterranean clover grown separately and together. Furthermore, we quantified low-molecular-weight organic acids (LMWOA) in root exudates. To test the effect of root exudates in plant-plant chemical signaling, both species were grown in Hoagland hydroponic solution. The experimental design contained three treatments: T1 (subterranean clover, monocropping); T2 (grapevine, monocropping) and T3 (subterranean clover + grapevine, intercropping). The exudate profile showed that the main compounds were amino acid, flavonoids and organic acids in all treatments. Specifically, amino acids exudates (∼20%) were l-threonine by subterranean clover in monocropping (T1) and glutathione in intercropping with grapevine (T3). Glycylglycine was detected in exudates released by subterranean clover (T1) and both plants under intercropping (T3). Regarding flavonoids (∼10%), epicatechin was detected only in subterranean clover exudates (T1). Interestingly, we detected kaempferol-3-glucuronide, l-2-aminoadipic and gluconic acids were found only under intercropping. The LMWOA were oxalic, malic, citric, and succinic. Oxalic acid was released in higher concentration. We highlight that succinic acid reached the highest concentration under intercropping on day-30. These results strongly suggest that amino acids, flavonoids and organic acids acts as signaling compounds between plant-plant interaction, can be utilized for improving grapevine plant performance.