RESUMEN
Low tunnels covered with spun-bonded fabric (row covers) provide season extension for vegetable production and also afford a physical barrier against airborne insects and other non-soil pests. Brussels sprouts, Brassica oleracea L. group Gemmifera (Brassicaceae), is a popular vegetable in local markets in Virginia; however, unprotected field production is severely affected by insect pest infestation. This study's objective was to determine the level of protection low tunnels provide against insect infestation and leaf herbivory injury. The experiment was conducted at the Virginia Tech Eastern Shore Agricultural Research and Extension Center in Painter, Virginia. The experimental design was split-plot with polyethylene soil mulches (white or black) as whole plot factors and production systems (low tunnel or open field) as subplot factors. In this study, low tunnels reduced insect infestation and chewing herbivory leaf injury to Brussels sprouts. Compared to an unprotected open field, infestations of lepidopteran insects and harlequin bug, Murgantia histrionica (Hahn) (Hemiptera: Pentatomidae) were reduced on plants under low tunnels. However, aphids (Hemiptera: Aphidae) infestation occurred under low tunnels in fall. There was no effect of color mulches (white or black) and no interaction between tunnel and mulch color on insect infestation and chewing injury. Fewer insect infestations and feeding injury indicate that low tunnels can be an effective management tool for sustainable vegetable production.
Asunto(s)
Brassica , Heterópteros , Insecticidas , Animales , Insectos , VirginiaRESUMEN
Polygalacturonase (PG) and pectin methylesterase (PME) activities were analyzed in ripening fruits of two tabasco pepper (Capsicum frutescens) lines that differ in the extent of pectin degradation (depolymerization and dissolution). Ripe 'Easy Pick' fruit is characterized by pectin ultra-degradation and easy fruit detachment from the calyx (deciduous trait), while pectin depolymerization and dissolution in ripe 'Hard Pick' fruit is limited. PG activity in protein extracts increased similarly in both lines during fruit ripening. PME activity in vivo assessed by methanol production, however, was detected only in fruit of the 'Easy Pick' line and was associated with decreased pectin methyl-esterification. In contrast, methanol production in vivo was not detected in fruits of the 'Hard Pick' line and the degree of pectin esterification remained the same throughout ripening. Consequently, a ripening specific PME that is active in vivo appears to enhance PG-mediated pectin ultra-degradation resulting in cell wall dissolution and the deciduous fruit trait. PME activity in vitro, however, was detected in protein extracts from both lines at all ripening stages. This indicates that some PME isozymes are apparently inactive in vivo, particularly in green fruit and throughout ripening in the 'Hard Pick' line, limiting PG-mediated pectin depolymerization which results in moderately difficult fruit separation from the calyx.