The Impact of Climate Change on Vegetable Crop Diseases and Their Management: The Value of Phytotron Studies for the Agricultural Industry and Associated Stakeholders

Climate change is having a significant impact on global agriculture, particularly on vegetable crops, which play a critical role in global nutrition. Recently, increasing research has concentrated on the impact of climate change on vegetable crop diseases, with several studies being conducted in phytotrons, which have been used to explore the effects of increased temperatures and CO2 concentrations to simulate future scenarios. This review focuses on the combined effects of temperature and carbon dioxide increases on foliar and soilborne vegetable diseases, as evaluated under phytotron conditions. The influence of climate change on mycotoxin production and disease management strategies is also explored through case studies. The results offer valuable information that can be used to guide both seed and agrochemical industries, as well as to develop disease-resistant varieties and innovative control measures, including biocontrol agents, considering the diseases that are likely to become prevalent under future climatic scenarios. Recommendations on how to manage vegetable diseases under ongoing climate change are proposed to facilitate plants' adaptation to and enhanced against the changing conditions. A proactive and comprehensive response to climate-induced challenges in vegetable farming is imperative to ensure food security and sustainability.

Revisiting Changes in Growth, Physiology and Stress Responses of Plants under the Effect of Enhanced CO2 and Temperature

Climate change has universally affected the whole ecosystem in a unified manner and is known to have improbable effects on agricultural productivity and food security. Carbon dioxide (CO2) and temperature are the major environmental factors that have been shown to increase sharply during the last century and are directly responsible for affecting plant growth and development. A number of previous investigations have deliberated the positive effects of elevated CO2 on plant growth and development of various C3 crops, while detrimental effects of enhanced temperature on different crop plants like rice, wheat, maize and legumes are generally observed. A combined effect of elevated CO2 and temperature has yet to be studied in great detail; therefore, this review attempts to delineate the interactive effects of enhanced CO2 and temperature on plant growth, development, physiological and molecular responses. Elevated CO2 maintains leaf photosynthesis rate, respiration, transpiration and stomatal conductance in the presence of elevated temperature and sustains plant growth and productivity in the presence of both these environmental factors. Concomitantly, their interaction also affects the nutritional quality of seeds and leads to alterations in the composition of secondary metabolites. Elevated CO2 and temperature modulate phytohormone concentration in plants, and due to this fact, both environmental factors have substantial effects on abiotic and biotic stresses. Elevated CO2 and temperature have been shown to have mitigating effects on plants in the presence of other abiotic stress agents like drought and salinity, while no such pattern has been observed in the presence of biotic stress agents. This review focuses on the interactive effects of enhanced CO2 and temperature on different plants and is the first of its kind to deliver their combined responses in such detail.

Monitoring and Surveillance of Aerial Mycobiota of Rice Paddy through DNA Metabarcoding and qPCR

The airborne mycobiota has been understudied in comparison with the mycobiota present in other agricultural environments. Traditional, culture-based methods allow the study of a small fraction of the organisms present in the atmosphere, thus missing important information. In this study, the aerial mycobiota in a rice paddy has been examined during the cropping season (from June to September 2016) using qPCRs for two important rice pathogens (Pyricularia oryzae and Bipolaris oryzae) and by using DNA metabarcoding of the fungal ITS region. The metabarcoding results demonstrated a higher alpha diversity (Shannon–Wiener diversity index H′ and total number of observed species) at the beginning of the trial (June), suggesting a higher level of community complexity, compared with the end of the season. The main taxa identified by HTS analysis showed a shift in their relative abundance that drove the cluster separation as a function of time and temperature. The most abundant OTUs corresponded to genera such as Cladosporium, Alternaria, Myrothecium, or Pyricularia. Changes in the mycobiota composition were clearly dependent on the average air temperature with a potential impact on disease development in rice. In parallel, oligotyping analysis was performed to obtain a sub-OTU identification which revealed the presence of several oligotypes of Pyricularia and Bipolaris with relative abundance changing during monitoring.

Ready-to-Eat Salad Crops: A Plant Pathogen's Heaven

The ready-to-eat salad sector, also called fresh-cut or bagged salads, is a fast-growing segment of the fresh-food industry. The dynamism and specialization of this sector, together with the lack of adequate crop rotation, the globalization of the seed market, and climate change, are the main causes of the development of many new diseases that cause severe production losses. Newly detected diseases of the most important crops grown (lettuce, wild and cultivated rocket, lamb's lettuce, chicory, endive, basil, spinach, and Swiss chard) are critically discussed. The management of these diseases represents a formidable challenge, since few fungicides are registered on these minor-use crops. An interesting feature of the ready-to-eat salad sector is that most crops are grown under protection, often in soilless systems, which provide an environment helpful to the implementation of innovative control methods. Current trends in disease management are discussed, with special focus on the most sustainable practices.

Emergence of Leaf Spot Disease on Leafy Vegetable and Ornamental Crops Caused by Paramyrothecium and Albifimbria Species

The genera Paramyrothecium and Albifimbria have been established from the former genus Myrothecium and they generally comprise common soil-inhabiting and saprophytic fungi. Within these genera, only two fungi have been recognized as phytopathogenic thus far: P. roridum and A. verrucaria, both of which cause necrotic leaf spots and plant collapse. Severe leaf necrosis and plant decay have been observed in Northern and Southern Italy on leafy vegetable crops. Thirty-six strains of Paramyrothecium- and Albifimbria-like fungi were isolated from affected plants belonging to eight different species. Based on morphological characteristics, 19 strains were assigned to A. verrucaria, whereas the remaining strains, which mostly resembled Paramyrothecium-like fungi, could not be identified precisely. Molecular characterization of six loci (internal transcribed spacer [ITS], β-tubulin [tub2], calmodulin [cmdA], translation elongation factor 1-alpha [tef1], large subunit ribosomal RNA [LSU], and mitochondrial ATP 6synthase 6 [ATP6]) of the 36 new isolates and three previously ITS-characterized isolates assigned all strains to four species: A. verrucaria, P. roridum, P. foliicola, and P. nigrum. Single and concatenated phylogenetic analyses were conducted, and they clearly distinguished the isolated fungi into four different groups. A. verrucaria, P. roridum, P. foliicola, and P. nigrum were able to induce leaf necrosis singly, and they were confirmed to be the causal agents of the leaf spot disease through pathogenicity assays. The involvement of fungi previously considered saprophytic (i.e., P. foliicola and P. nigrum) in the development of plant disease for the first time deserves particular attention because of the possibility of their transmission by seeds and the limited knowledge of their management with chemicals.