Seed treatment using methyl jasmonate induces resistance to rice water weevil but reduces plant growth in rice

Abstract

The jasmonic acid cascade plays a pivotal role in induced plant resistance to herbivores. There have been a number of investigations into the potential uses of derivatives of this hormone for pest management. Understanding the phenotypic plasticity of plant defense traits interactions in agricultural systems may facilitate the development of novel and improved management practices, which is desirable as management of insects in most agricultural systems is currently heavily reliant on insecticides. The rice water weevil (RWW), Lissorhoptrus oryzophilus Kuschel, is a pest of rice, Oryza sativa, in the southern U.S. and globally. The effects of the jasmonic acid derivative, methyl jasmonate (MJ), on induced defenses to RWW in rice, and the potential costs of MJ-induced resistance to plant growth and fitness, were tested in a series of field and greenhouse trials. It was hypothesized that seed treatments with MJ would reduce densities of larval RWW. A second hypothesis was that MJ seed treatments would alter emergence, biomass accumulation, and yield of rice. The final hypothesis was that induction of plant resistance to the RWW would diminish as the time from seed treatment increased. In order to investigate these hypotheses, RWW densities were determined in greenhouse and field trials. Plant growth was measured in the field by assessing plant emergence, root and shoot biomass, time of heading, and yield (grain mass). Results indicated that MJ seed treatments induced resistance to RWW, although this effect decayed over time. Additionally, there were costs to plant growth and fitness; emergence and heading were delayed and biomass was reduced. Importantly, however, yields on a per-plant were not significantly reduced by MJ treatment. Overall, these results are promising and show the potential for the use of jasmonate elicitors as part of a pest management program in rice.

Induced Resistance and Differential Allocation of Herbivore Defensive Chemicals: A Case Study With Internode Borer Chilo Sacchariphagus Indicus (Kapur) in Sugarcane

“…Further studies with a range of concentrations and application at different plant stages with observations over an extended period under INB feeding regimes would serve as the forerunner for field level application of inducer molecules. While pursuing this objective, the aspect of costs to plant growth and fitness under MeJA application, in addition to resistance induction against target pest (Kraus and Stout 2019), needs to be addressed in long-term studies.…”

“…External application of MeJA on plants has been known to induce resistance against crop pests (Erb and Reymond 2019). For example, seed treatment of rice with MeJA induced resistance to rice water weevil but with costs to plant growth and fitness (Kraus and Stout 2019).…”

Seed Treatment With Jasmonic Acid and Methyl Jasmonate Induces Resistance to Insects but Reduces Plant Growth and Yield in Rice, Oryza sativa

“…In a previous study, Kraus and Stout (2019) showed that, under field conditions, MeJA-treated rice seeds enhanced resistance to the rice water weevil in rice plants, leading to reductions in population densities of rice water weevils on rice roots. The resistance induced by the MeJA seed treatment came, however, with a cost to plant growth.…”

“…Recently, studies have attempted to use application of JA or MeJA to seeds before germination to induce resistance in plants. Seed treatments with plant elicitors have mostly been investigated in tomato, Solanum lycopersicum L., with a few additional studies on cabbage, Brassica oleracea and rice, Oryza sativa L. These studies provide evidence that seed treatment with JA or MeJA can increase resistance against herbivores in plants ( Worrall et al, 2012;Paudel et al, 2014;Strapasson et al, 2014;Haas et al, 2018;Kraus and Stout, 2019). However, variations in JA-induced responses existed among cultivars within a plant species as well as among plant species as seeds of different varieties were not equally receptive to seed treatment with plant elicitors (Smart et al, 2013;Mouden et al, 2020).…”

“…However, variations in JA-induced responses existed among cultivars within a plant species as well as among plant species as seeds of different varieties were not equally receptive to seed treatment with plant elicitors (Smart et al, 2013;Mouden et al, 2020). Moreover, unlike applications of plant elicitors by foliar spray or soil drench, which are usually made at or near the time of pest infestation, seed treatments are made before seeds are planted, and hence, the duration of induction of defenses by seed treatments is a critical consideration for the efficacy of seed treatments (Worrall et al, 2012;Haas et al, 2018;Kraus and Stout, 2019).…”