Microscopic and biochemical aspects of sorghum resistance to anthracnose mediated by silicon

Abstract

The use of silicon (Si) in agriculture has attracted a great deal of interest from researchers because of the numerous benefits of this element to plants, especially when they are submitted to abiotic and/or biotic types of stress. The host's increased resistance to diseases, promoted by Si, is mainly associated with the deposition of this element in the tissues and the potentiation of defence mechanisms. However, the mechanisms involved in Si-mediated host resistance need to be further investigated. Thus, this study aimed to microscopically and biochemically elucidate the resistance of sorghum to anthracnose. In the leaves of plants supplied with Si, in addition to a greater deposition of Si at the infection sites, the acervuli were smaller in number compared to the leaves of plants not supplied with Si. Additionally, the activities of the defence enzymes peroxidases and polyphenoloxidases and the concentration of anthocyanins were higher in the leaves of plants supplied with Si. It can be concluded that Si, in addition to participate in the physical barrier that slows or prevents Colletotrichum sublineolum penetration in sorghum leaves, also plays a role in the biochemical aspect of sorghum resistance to anthracnose.

Silicon in plant disease control

“…Sorghum leaves inoculated with Colletotrichum sublineolum and supplemented with Si showed high Si deposition on infection sites and fewer and smaller acervuli compared with the non-treated leaves. In addition, there was a higher concentration of plant defense enzymes, peroxidases and polyphenol, and anthocyanin in Si-treated leaves (Resende et al, 2013). The authors also reported the joint action of physical and biochemical barriers promoted by Si action, reducing C. sublineolum infection.…”

“…effect on disease reduction to the formation of both physical barriers, by deposition of Si (Sangster et al, 2001;Kim et al, 2002;Pozza et al, 2004;Carré-Missio et al, 2012b), and chemical barriers such as defense enzymes (Cherif et al, 1994;Fauteux et al, 2005;Cai et al, 2008;Shetty et al, 2011;Polanco et al, 2012). The joint action of these barriers in disease control in plants fertilized with Si was observed by Cai et al (2008) and Resende et al (2013). Moreover, silicon is reported to interfere with the absorption of essential nutrients to plants, including horizontal resistance to form barriers as the wax layer and the cell wall, among others (Pozza et al, 2007;Moraes et al, 2009;Botelho et al, 2005).…”

“…Resende et al (2013) reported that sorghum grown in nutrient solution added with Si (2 mmol L -1 ) had severity of anthracnose (Colletotrichum sublineolum) around 20%, while the control was 93%, at 10 days after inoculation. There are also reports of reduction of disease severity in sugarcane rust (Puccinia melanocephala) (Naidoo et al, 2009), control of Blumeria graminis f.sp.. sp.…”

“…tritici in wheat (Belanger et al, 2003) and control of Erysiphe graminis in barley (Carver et al, 1987). Then, promising results in reducing disease intensity were found in various pathosystems, also in dicots, including Cercospora leaf spot and rust in coffee (Pozza et al, 2004;Botelho et al, 2005;Amaral et al, 2008;CarreMissio et al, 2014), pestalotiopsis leaf spot and powdery mildew in strawberry (Palmer et al, 2006;Kanto et al, 2006;Kanto et al, 2007;Carré-Missio et al, 2010), powdery mildew in melon, squash and cucumber Samuels et al, 1991), rust in soybean Lima et al, 2010), anthracnose in common-bean and sorghum (Moraes et al, 2009;Polanco et al, 2012;Resende et al, 2013) and root rot in tomato and avocado (Heine et al, 2007;Bekker et al, 2006).…”

Silicon‐mediated cell wall modifications of sorghum root exodermis and suppression of invasion by fungus Alternaria alternata

“…Deposition of these substances interrupts the open channel network present in plant cell walls, thus contributing to more precise regulation between cellular and apoplasmic pathways for water, solutes and toxins (Ranathunge et al ., ). Apart from the aforementioned modifications, cell walls of plants may be also strengthened by silicon deposition (Resende et al ., ; Najihah et al ., ). However, its specific binding form and site in the plant cell wall are not completely elucidated (Guerriero et al ., ).…”