Exploring Chenopodium album adaptive traits in response to light and temperature stresses

Weeds within canopies are depleted in photosynthetic photon flux density (PPFD) and red to far‐red light ratio (R/FR) throughout their lifespan. Growth cabinet studies isolated PPFD and R/FR effects and explored the adaptive traits of a model invasive weed, Chenopodium album, to light and temperature. Reproductive development progressed rapidly at high temperature, yet the rate of leaf appearance was insensitive to temperatures of 25:15 and 10:5°C (day:night). Low R/FR effects were detected early in the life cycle, but by seed set, growth was influenced by low PPFD. C. album adapted to the simulated canopy environments by delaying seed set, growing taller and producing more leaf area per mol of accumulated incident PPFD. Low PPFD reduced seed number per plant and the carbon/nitrogen ratio of those seeds, but not seed weight. PPFD was a primary cue for many shade avoidance traits and only under low PPFD did R/FR modify the expression of these traits. This study elucidates the adaptive strategies that make C. album a persistent weed.     

Characterization and pathogenicity assessment of Plectosphaerella species associated with stunting disease on tomato and pepper crops in Italy

This study follows a survey carried out in 2012 and 2013 on tomato and pepper crops in the Foggia province (southern Italy), for morphological, molecular and pathogenicity analyses of Plectosphaerella fungi. The Plectosphaerella genus includes several species that are pathogens of horticultural plants. The survey identified tomato and pepper crops that showed abundant wilt, leaf yellowing, and discolouration and necrosis of roots, plus collar and stem symptoms. Different fungi including Plectosphaerella spp. were isolated from tissues with and without symptoms. Subsequent molecular and morphological studies identified first records of P. citrulli infecting tomato and pepper, and P. pauciseptata and P. ramiseptata infecting pepper. Pathogenicity testing confirmed that most isolated species of Plectosphaerella caused symptoms on tomato and pepper, with P. ramiseptata the most aggressive. On the basis of these data, it is considered that Plectosphaerella species may cause stunting disease in tomato and pepper.