Companion cropping with potato onion enhances the disease resistance of tomato against Verticillium dahliae

Abstract

Intercropping could alleviate soil-borne diseases, however, few studies focused on the immunity of the host plant induced by the interspecific interactions. To test whether or not intercropping could enhance the disease resistance of host plant, we investigated the effect of companion cropping with potato onion on tomato Verticillium wilt caused by Verticillium dahliae (V. dahliae). To investigate the mechanisms, the root exudates were collected from tomato and potato onion which were grown together or separately, and were used to examine the antifungal activities against V. dahliae in vitro, respectively. Furthermore, RNA-seq was used to examine the expression pattern of genes related to disease resistance in tomato companied with potato onion compared to that in tomato grown alone, under the condition of infection with V. dahliae. The results showed that companion cropping with potato onion could alleviate the incidence and severity of tomato Verticillium wilt. The further studies revealed that the root exudates from tomato companied with potato onion significantly inhibited the mycelia growth and spore germination of V. dahliae. However, there were no significant effects on these two measurements for the root exudates from potato onion grown alone or from potato onion grown with tomato. RNA-seq data analysis showed the disease defense genes associated with pathogenesis-related proteins, biosynthesis of lignin, hormone metabolism and signal transduction were expressed much higher in the tomato companied with potato onion than those in the tomato grown alone, which indicated that these defense genes play important roles in tomato against V. dahliae infection, and meant that the disease resistance of tomato against V. dahliae was enhanced in the companion copping with potato onion. We proposed that companion cropping with potato onion could enhance the disease resistance of tomato against V. dahliae by regulating the expression of genes related to disease resistance response. This may be a potential mechanism for the management of soil-borne plant diseases in the intercropping system.

Physiological response and sulfur metabolism of the V. dahliae-infected tomato plants in tomato/potato onion companion cropping

“…Additional analyses showed that companion cropping with potato onions decreased the disease incidence and index (Fig. 1), confirming the results of the previous study5. These results indicated that companion cropping with potato onions increases the accumulation of substances related to resistance, thereby increasing the resistance of tomato plants against V. dahliae.…”

“…For example, root interactions between maize and soybean increase the resistance of soybean to Cylindrocladium parasiticum 10, and maize and pepper interactions enhance maize resistance to Bipolaris maydis 9. Similarly, in a previous study, we have shown that tomato and potato onion interactions enhance tomato resistance to V. dahliae by up-regulating disease resistance-related genes under the tomato/potato onion companion cropping5. To explore the physiological defense responses of tomato to V. dahliae infection, we examined changes in the content of total phenol, lignin, GSH, and MDA, and the enzymatic activities of SOD, POD, PPO and PAL, all of which are key enzymes related to disease resistance12122.…”

“…Notably, the SOD activity was lower in tomatoes grown with potato onion plants than in monocultured tomatoes (Fig. 3A), probably because of enhanced pathogen defense and decreased V. dahliae attack5.…”

“…Several management strategies have been developed for controlling this disease, such as cultivating the cultivars with Ve gene1, inducing plant resistance by using beneficial bacteria23, intercropping456, and enhancing plant defense against V. dahliae by using sulfur78. These strategies would lower production costs and reduce environmental pollution.…”

“…Several studies have demonstrated that intercropping and companion cropping may alleviate soil-borne diseases by enhancing plant disease resistance to pathogens45910. Previous studies have shown that companion cropping with potato onions alleviates tomato Verticillium Wilt by up-regulating the expression levels of genes related to disease resistance (encoding proteins such as pathogenesis-related proteins and those involved in lignin biosynthesis, phytohormone metabolism and signal transduction) in tomatoes infected with V. dahliae 5, and by the inhibition effect of tomato root exudates on V. dahliae . However, the physiological responses of tomato to V. dahliae infection in the tomato/potato onion companion cropping system remain unknown.…”