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.
Highlights
In modern agriculture intercropping has long been used for the increase of crop productivity and management of soilborne diseases (Boudreau, 2013; Li et al, 2014)
Compared to TM, the disease incidences in TC were decreased by 24.97 and 27.13% in 2013, by 35.58 and 19.83% in 2014 at 18 and 28 days after the inoculation (DAI), respectively (Figures 1A,B)
When the concentration was decreased to 1 g FW·20 mL-1, the root exudates from TC had no significant inhibition effect on the V. dahliae race 1 (Vd1) mycelia growth
Summary
In modern agriculture intercropping has long been used for the increase of crop productivity and management of soilborne diseases (Boudreau, 2013; Li et al, 2014). It was widely observed that intercropping was beneficial for the management of soil-borne disease, such as inhibition of pepper Phytophthora blight in maize/pepper intercropping system (Yang et al, 2014), suppression of watermelon Fusarium wilt in rice/watermelon intercropping (Ren et al, 2008), and inhibition of soybean red crown rot in maize/soybean intercropping (Gao et al, 2014) and so on. The main focus was on the effects of root exudates from companied plant on the pathogen which attacks the host plant (Ren et al, 2008; Hao et al, 2010; Gao et al, 2014; Yang et al, 2014). Whether or not the root exudates from host plant have antifungal activity on pathogen in intercropping was unknown
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