A potential strategy for controlling pests is through the use of “companion plants” within a crop system. This strategy has been used in several trials to fight against a major crop insect pest: the aphid. We reviewed the literature to highlight the major mechanisms by which a companion plant may act. Trials carried out under laboratory or field conditions revealed that companion plants operate through several mechanisms. A companion plant may be associated with a target crop for various reasons. Firstly, it can attract aphids and draw them away from their host plants. Secondly, it can alter the recognition of the host plant. This effect is mostly attributed to companion plant volatiles since they disturb the aphid host plant location, and additionally they may react chemically and physiologically with the host plant, making it an unsuitable host for aphids. Thirdly, it can attract natural enemies by providing shelter and food resources. In this review, the feasibility of using companion plants is discussed. We conclude that many factors need to be taken into account for a successful companion plant strategy. For the best long-term results, companion plant strategies have to be combined with other alternative approaches against aphids.

BACKGROUND: Intercropping companion plants (CPs) with horticultural crops could be an eco‐friendly strategy to optimize pest management. In this research, volatile organic compounds (VOCs) emitted by some CPs were investigated for their repellent properties towards the green peach aphid (Myzus persicae Sulzer). The aim of this study was to understand the modes of action involved: direct effects on the aphid and/or indirect effects via the host plant (pepper, Capsicum annuum L.).RESULTS: We identified two promising repellent CP species: the volatile blend from basil (Ocimum basilicum, direct repellent effect) and the mixture of (or previously intercropped) C. annuum plants with Tagetes patula cv. Nana (indirect effect). This effect was cultivar‐dependent and linked to the volatile bouquet. For the 16 compounds present in the O. basilicum or T. patula bouquets tested individually, (E)‐β‐farnesene, and eugenol reported good repellent properties against M. persicae. Other compounds were repellent at medium and/or highest concentrations. Thus, the presence of repellent VOCs in a mixture does not mean that it has a repellent propriety.CONCLUSION: We identified two promising repellent CP species towards M. persicae, with a likely effect of one CP's VOCs on the host plant repellency and highlighted the specific effectiveness of VOC blends. © 2018 Society of Chemical Industry

Precision horticulture is fundamental to ensure high quality production with a minimal environmental footprint. It offers the possibility to manage climatic and fertilization inputs closer to the plant needs. In practice, there is a tendency to over-fertilize, as nitrogen limitation can decrease photosynthesis and consequently fruit yield, but also because nutrient recycling does not lead to any substantial costs increase, thus ignoring the influence of nitrogen input on the balance between growth and metabolism. Nitrogen recommendation for tomato greenhouse production on rockwool is 16mM, even it is well established that only 50% of nitrogen amount is really absorbed by plants. This study compares the usual practice (16 mM) to a nitrogen supply to meet plant’s needs (5 mM). We analyzed plant growth and development, yield, leaf photosynthetic activity and fruit quality (sugars, acids, vitamin C,) over the entire crop period (December to October). Over-fertilization favoured the accumulation of nitrogen in leaves and stem but yield, leaf photosynthetic activity and plant architecture were not significantly improved. In addition, it decreased the quality of the tomatoes as the sugar:acid ratio decreased dramatically in the pericarp, whereas the locular gel composition remained similar. A reduction of the nitrogen supply is one solution to improve tomato quality without any reduction of yield in greenhouse. These data have to be incorporated in tomato fertigation management to define a new standard based on overall quality of tomato fruit and low environmental footprint.

In this study, we investigated how increasing temperature affects tomato fruit physicochemical traits and looked for genetic variability to help maintain fruit quality in the context of climate change. High temperature (HT: +3 °C) was applied at four fruit developmental stages, from anthesis and 15, 30 or 45 days after anthesis until ripening to three genotypes, a commercial cultivar (Money Maker, “MM”) and two genotypes likely more tolerant to HT (Campeche 40 “C40”, a landrace from a warm, humid region, and a hybrid Chapingo F1, “F1”, resulting from crossbreeding landraces tolerant to high temperature). Increasing average diurnal temperature (from 27.0 to 29.9) reduced fruit firmness and size and affected fruit composition according to genotype. Sugar and acid contents were highly impacted in MM and C40 fruits, especially when HT was applied during the rapid fruit growth period. The application of HT at different fruit developmental stages revealed that HT could enhance acid accumulation and degradation (rate and/or duration), resulting in different effects on fruit acidity between genotypes. The F1 genotype appeared to be more adapted to HT, producing larger fruits with higher sugar, lower acid and increased vitamin C and calcium content. These results provide interesting directions for breeding programs that want to maintain future tomato fruit yields and quality.