Content area
Full text
(ProQuest: ... denotes non-US-ASCII text omitted.)
Research Paper
Introduction
Several biotic factors, such as beneficial microorganisms, infection by microbial pathogens or infestation by insect pests (Kessler & Baldwin, 2002; Dicke & Hilker, 2003; Pozo et al., 2004), can induce resistance in plants against diseases and insect pests (van der Ent et al., 2009; Cohen et al., 2010). Induced resistance can also be activated by chemicals such as [beta]-aminobutyric acid (BABA), a non-protein amino acid (Zimmerli et al., 2000). BABA has been documented to induce plant resistance mechanisms in the following host/pest systems: Bremia lactucae, an Oomycete, on lettuce (Cohen et al., 2010, 2011); Phytophthora infestans on tomatoes (Cohen et al., 1994); Acyrthosiphon pisum (Harris), a pea aphid, on legumes (Hodge et al., 2005); Myzus persicae (Sulz.), Brevicoryne brassicae (L.), Trichoplusia ni (Hübner) and Plutella xylostella (L.) on several species in the Brassicaceae (Hodge et al., 2006); and Heterodera avenae Woll., Heterodera latipons and Meloidogyne sp., which are plant parasitic nematodes, on wheat and barley (Oka & Cohen, 2001). In addition, BABA is known to induce resistance against abiotic stresses such as drought, heat, salinity and acid rain (Jakab et al., 2001; Liu et al., 2011).
BABA induces resistance in plants through a number of physical and biochemical mechanisms (Cohen, 2002). Accumulation of pathogenesis-related (PR) proteins is one of the responses elicited by the application of BABA to plants (Cohen et al., 1994; Hwang et al., 1997). Expression of systemic acquired resistance (SAR) in plants as a result of BABA application is related to elevated expression levels of the PR-1, PR-2, and PR-5 genes (Jakab et al., 2001). BABA-related elevation of PR protein levels can occur in tomato, pepper and tobacco plants in the absence of biotic stress by a plant pathogen (Cohen et al., 1994; Hwang et al., 1997), whereas in crucifers, PR protein levels were elevated only after the addition of biotic stress of pathogen infection (Zimmerli et al., 2000, 2001; Silue et al., 2002). BABA also increases lignin and callose content in foliar tissues and vascular walls, respectively, which can adversely affect feeding by herbivores (Cohen et al., 1999; Hamiduzzaman et...