A Monocot Plant Identified as an Alternate Host of the Causal Agent of Bacterial Spot of Tomato and Pepper

Abstract

<jats:p><jats:italic>Xanthomonas campestris</jats:italic> pv. <jats:italic>vesicatoria</jats:italic> (Xcv) recovered from <jats:italic>Commelina benghalensis</jats:italic> L., caused bacterial spot disease in cultivars of pepper and tomato susceptible to the pathogen. This is the first reported case of a dicot-infecting Xc pathovar infecting a monocot plant, represented here by a member of the Family Commelinaceae. Laboratory strains of the pathogen that included 81-23, 81-23M13, 82:4, 2595, and P6AD4, known to be pathogenic to pepper and tomato, promoted bacterial spot symptoms on leaves of <jats:italic>C. benghalensis</jats:italic> L. Of the 63 field isolates recovered from infected <jats:italic>C. benghalensis</jats:italic> L., 30 gave biochemical and physiological reactions consistent with Xcv pathogens, whereas 10 of the latter promoted bacterial spot disease in the test cultivars resulting in the identification of seven pathogenic races, including P2, P5, P6, P5T1, P5T2, P6T2, and P6T3. Bacterial spot disease symptoms developed on stems only when <jats:italic>C. benghalensis</jats:italic> L. was spray-inoculated with strains 81-23, 81-23M13, and P6AD4. Bacterial concentration increased in planta by as much as 10<jats:sup>3</jats:sup> per lesion of the leaf, whereas growth of the same strains was restricted in the stem of this weed. Growth of these three strains was, however, significantly (<jats:italic>P</jats:italic> ≤ 0.05) lower on NYGA amended with <jats:italic>C. benghalensis</jats:italic> L. stem extract than on NYGA amended with leaf extract. The ability of the bacterial spot pathogen to infect the stem of <jats:italic>C. benghalensis</jats:italic> L. has serious implications for management of bacterial spot disease in fields populated with this weed since stems of this plant infected with the pathogen continue to grow vegetatively and disperse throughout all fields in which it is found.</jats:p>

Resistance of Benghal Dayflower (Commelina benghalensis) Seeds to Harsh Environments and the Implications for Dispersal by Mourning Doves (Zenaida macroura) in Georgia, U.S.A

“…The weed is a tenacious competitor with crop plants, becoming entrenched in agricultural fields because of its tolerance to many commonly used herbicides, particularly glyphosate (Owen and Zelaya 2005;Webster et al 2005); its ability to propagate vegetatively from broken stem pieces (Budd et al 1979); and its variable growth habit with negative, positive, and diagravitropic branches that produce both aerial and underground flowers, fruits, and seeds (Maheshwari and Singh 1934). Additionally, Benghal dayflower can harbor plant pathogens (Davis et al 2006;Desaeger and Rao 2000) and has been associated with outbreaks of epidemic proportion in agricultural crops (Gibbs 2002;Kucharek et al 1998).…”