Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2011
Publication Date: 6/1/2011
Publication URL: http://hdl.handle/net/10113/50042
Citation: Srivastava, P., George, S., Marois, J.J., Wright, D.L., Walker, D.R. 2011. Saccharin-induced systemic acquired resistance against rust (Phakopsora pachyrhizi) infection in soybean: Effects on growth and development. Crop Protection. 30(6):726-732. Interpretive Summary: The ability of applications of a saccharin solution to induce systemic acquired resistance to the soybean rust fungus, Phakopsora pachyrhizi, in soybean plants was investigated.Saccharin was applied to plants growing in a greenhouse hydroponics system as either a foliar spray or a root drench at either the 2nd trifoliolate or early flowering stages, and the plants were then inoculated with the pathogen 1, 5, 10 and 15 days afterwards. Although both modes of application appeared to boost systemic protection by 15 days after the treatment, the effect of the root drench was much more rapid, with increased resistance to the fungus observed after one day. Saccharin treatment did not adversely affect plant growth and development, with the exception of the root drench applied at the early flowering stage. Further investigations should provide useful information about whether and how this technique for reducing the severity of rust on soybean can be implemented in commercial production conditions.
Technical Abstract: We examined the effect of saccharin on the systemic acquired resistance (SAR) response of soybean to the fungus Phakopsora pachyrhizi, the causal agent of soybean rust. Plants were grown hydroponically in half-strength Hoagland’s solution and were challenged with the pathogen 1, 5, 10 and 15 days after treatment with 3 mM saccharin applied either as a foliar spray or a root drench at the 2nd trifoliate (V3) and early reproductive (R1) stages. Plants were destructively harvested and assessed for visible rust symptoms 2 weeks after inoculation with the pathogen. Mode of saccharin applications were significant factors influencing the severity of rust infection. Saccharin applied as a root drench was more effective than the foliar spray treatment at inducing SAR, with increased resistance observed 1 day after application. Systemic protection against rust infection was still apparent 15 days after application of saccharin as a root drench. In contrast, foliar treatment with saccharin did not increase systemic protection until 15 days after treatment. When systemic protection was induced by the application of saccharin in either manner, there was no significant reduction of plant growth except when saccharin was applied as a drench 15 days after treatment at the R1 stage of development.