Serious, postharvest decay losses occurred in tomatoes when water in which they were submerged was cooler than the fruit. Tomatoes have extensive intercellular air spaces, a heavily cutinized epidermis, and no stomatal openings. When tomatoes with unbroken skins were submerged in packinghouse dump tank water of lower temperatures, the internal air contracted and water plus decay organisms were drawn into the fruits through the stem scar. Heating dump tank water has been successful in limiting this decay problem.
Robert K. Showalter
Suparna R. Mundodi, Jeffrey A. Anderson, Niels O. Maness, Michael W. Smith, Bjorn Martin, Marlee L. Pierce, and Andrew J. Mort
The hypersensitive response in resistant plants exposed to incompatible pathogens involves structural changes in the plant cell wall and plasma membrane. Cell wall changes may include pectin deesterification resulting in release of methanol. The time course of methanol production was characterized from `Early Calwonder 20R' pepper (Capsicum annuum L.) leaves infiltrated with the incompatible pathogen, Xanthomonas campestris pv. vesicatoria (Doidge) Dye race 1 (XCV). In the first time course experiment, leaves were infiltrated with either 108 colony-forming units/mL of XCV or water control. Leaf panels (1 × 5 cm) were excised after dissipation of water soaking, then incubated in vials at 24 °C. Headspace gas was analyzed at 6-hour intervals up to 24 hours. The rate of methanol production from resistant pepper leaves infiltrated with XCV was greatest during the first 12 hours after excision. In another experiment, leaf panels were harvested at 6-hour intervals up to 24 hours after inoculation and incubated for 12 hours at 24 °C to determine the relationship between the interval from inoculation to leaf excision and methanol production. The highest rate of methanol production was obtained when the interval between bacterial infiltration and leaf excision was 18 hours. The relationship between methanol release and changes in the degree of methylesterification (DOM) of cell wall pectin was determined in near isogenic lines of `Early Calwonder' pepper plants resistant (20R) and susceptible (10R) to XCV race 1. Cell walls were prepared from resistant and susceptible pepper leaves infiltrated with XCV or water. XCV-treated resistant leaves had 18% DOM and 9.7 nmol·g-1·h-1 of headspace methanol, and the susceptible leaves had 48% DOM with 0.2 nmol·g-1·h-1 methanol. Susceptible and resistant control leaves infiltrated with water had 55% and 54% DOM, respectively, with no detectable methanol production. Increased methanol production in resistant pepper leaves inoculated with XCV coincided with an increase in cell wall pH. Intercellular washing fluid of resistant pepper leaves had a significantly higher pH (6.9) compared to susceptible leaves (pH 5.1) and control leaves infiltrated with water (pH 5.1). Both 10R and 20R pepper leaves infiltrated with buffer at increasing pH's of 5.1, 6.9 or 8.7 had increased methanol production. Since deesterified pectin is more susceptible to degradation, demethylation may facilitate formation of pectic oligomers with defensive signalling activity.
Hyun-Gyun Yuk, Benjamin R. Warren, and Keith R. Schneider
., 2006 ). Dye infiltration of laboratory-etched tomatoes. Dye solutions, such as aniline blue, have been used to evaluate the potential for bacterial infiltration of fruit surfaces ( Eblen et al., 2004 ; Penteado et al., 2004 ). In this study, the dye
Josh B. Henry, Penelope Perkins-Veazie, Ingram McCall, and Brian E. Whipker
biochemical compounds in lentil ( Lens culinaris Medik.) Bangladesh J. Bot. 40 23 27 Sepúlveda-Jiménez, G. Rueda-Benítez, P. Porta, H. Rocha-Sosa, M. 2004 Betacyanin synthesis in red beet ( Beta vulgaris ) leaves induced by wounding and bacterial infiltration