The influence of timing the application of nitrogen fertilizer on early blight (Alternaria solani)

Can we control potato fungal and bacterial diseases? - microbial regulation

The potato plant is one of the main crops in the world. However, relatively little is known about key virulence factors of major fungal and bacterial diseases in potatoes, biocontrol measures to improve activity and stability, and the core driving forces in the control process. Here, we focus on analyzing the mechanisms by which genes, proteins, or (and) metabolites of potato pathogens as key virulence factors. Then, the single strain biocontrol agents, synthetic microbial communities, microbial microcapsule strategies were introduced, and the latter two strategies can improve stability and activity in biocontrol. Meanwhile, summarized the defense mechanisms of biocontrol and their specific issues in practical applications. Furthermore, explore how potato crop management, soil management, and climate effects, as crucial driving forces affect potato biocontrol in the system. Dynamic and systematic research, excavation of biocontrol strain resources, find the causes of regional disease resistance and exploration of biocontrol mechanism will provide promising solutions for biotic stress faced by potato in the future.

Fungicide-free management of Alternaria leaf blotch and fruit spot on apple indicates Alternaria spp. as secondary colonizer

The fungal genus Alternaria is a pan-global pathogen of > 100 crops, and is associated with the globally expanding Alternaria leaf blotch in apple (Malus x domestica Borkh.) which leads to severe leaf necrosis, premature defoliation, and large economic losses. Up to date, the epidemiology of many Alternaria species is still not resolved as they can be saprophytic, parasitic or shift between both lifestyles and are also classified as primary pathogen able to infect healthy tissue. We argue that Alternaria spp. does not act as primary pathogen, but only as a necrosis-dependent opportunist. We studied the infection biology of Alternaria spp. under controlled conditions and monitored disease prevalence in real orchards and validated our ideas by applying fungicide-free treatments in 3-years field experiments. Alternaria spp. isolates were not able to induce necroses in healthy tissue, but only when prior induced damages existed. Next, leaf-applied fertilizers, without fungicidal effect, reduced Alternaria-associated symptoms (- 72.7%, SE: ± 2.5%) with the same efficacy as fungicides. Finally, low leaf magnesium, sulphur, and manganese concentrations were consistently linked with Alternaria-associated leaf blotch. Fruit spot incidence correlated positively with leaf blotch, was also reduced by fertilizer treatments, and did not expand during storage unlike other fungus-mediated diseases. Our findings suggest that Alternaria spp. may be a consequence of leaf blotch rather than its primary cause, as it appears to colonize the physiologically induced leaf blotch. Taking into account existing observations that Alternaria infection is connected to weakened hosts, the distinction may appear slight, but is of great significance, as we can now (a) explain the mechanism of how different stresses result in colonization with Alternaria spp. and (b) substitute fungicides for a basic leaf fertilizer. Therefore, our findings can result in significant decreases in environmental costs due to reduced fungicide use, especially if the same mechanism applies to other crops.

Stress Response to Climate Change and Postharvest Handling in Two Differently Pigmented Lettuce Genotypes: Impact on Alternaria alternata Invasion and Mycotoxin Production

Many species of Alternaria are important pathogens that cause plant diseases and postharvest rots. They lead to significant economic losses in agriculture and affect human and animal health due to their capacity to produce mycotoxins. Therefore, it is necessary to study the factors that can result in an increase in A. alternata. In this study, we discuss the mechanism by which phenol content protects from A. alternata, since the red oak leaf cultivar (containing higher phenols) showed lower invasion than the green one, Batavia, and no mycotoxin production. A climate change scenario enhanced fungal growth in the most susceptible cultivar, green lettuce, likely because elevated temperature and CO₂ levels decrease plant N content, modifying the C/N ratio. Finally, while the abundance of the fungi was maintained at similar levels after keeping the lettuces for four days at 4 °C, this postharvest handling triggered TeA and TEN mycotoxin synthesis, but only in the green cultivar. Therefore, the results demonstrated that invasion and mycotoxin production are cultivar- and temperature-dependent. Further research should be directed to search for resistant cultivars and effective postharvest strategies to reduce the toxicological risk and economic losses related to this fungus, which are expected to increase in a climate change scenario.

The role of abiotic and anthropogenic factors in the development of Alternaria leaf spot on potato plantings in the North-West of Russia

For effective control of the phytosanitary state of agrocenoses, it is important to have knowledge of the influence of abiotic and anthropogenic factors on the population density of pests, weeds and the development of diseases. Among all the factors influencing the development of Alternaria leaf spot in potato planting in the North-West of Russia, the most significant was the influence of weather conditions (55.5%). The intense development of this illness occurred in the years with the high average diurnal temperatures in the second and third decades of June along with the high level of precipitation in the first decade of July. The contribution of mineral nutrition and the integrated plant protection system turned out to be unequal, which accounted for 9.6 and 0.9%. At the same time, in some years, the application of mineral fertilizers determined the development of potato Alternaria leaf spot by 11.6–87.5%, and the implementation of protective measures – by 1.2–17.6%. The strong development of Alternaria leaf spot was influenced by the increased air temperatures in the second and third decades of June, combined with abundant humidity in the first decade of July. The introduction of complete mineral fertilization led to a significant decrease in the development of Alternaria leaf spot in potato plantings, while the effectiveness of fungicidal treatments was not high enough.

Review: Holistic pest management against early blight disease towards sustainable agriculture

Alternaria species are well-known aggressive pathogens that are widespread globally and warmer temperatures caused by climate change might increase their abundance more drastically. Early blight (EB) disease, caused mainly by Alternaria solani, and brown spot, caused by Alternaria alternata, are major concerns in potato, tomato and eggplant production. The development of EB is strongly linked to varieties, crop development stages, environmental factors, cultivation and field management. Several forecasting models for pesticide application to control EB were created in the last century and more recent scientific advances have included modern breeding technology to detect resistant genes and precision agriculture with hyperspectral sensors to pinpoint damage locations on plants. This paper presents an overview of the EB disease and provides an evaluation of recent scientific advances to control the disease. First of all, we describe the outline of this disease, encompassing biological cycles of the Alternaria genus, favorite climate and soil conditions as well as resistant plant species. Second, versatile management practices to minimize the effect of this pathogen at field level are discussed, covering their limitations and pitfalls. A better understanding of the underlying factors of this disease and the potential of novel research can contribute to implementing integrated pest management systems for an ecofriendly farming system. © 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Bokashi, Boiled Manure and Penergetic Applications Increased Agronomic Production Variables and May Enhance Powdery Mildew Severity of Organic Tomato Plants

Research on organic fertilizers are of crucial importance for sustainable production systems with high efficiency of natural resource use. The objective of this study was to evaluate organic sources of fertilization (boiled manure (BM), effective microorganism (EM) Bokashi, and Penergetic) for their effects on agronomic variables (fruit size and yield, total soluble solids) and on foliar powdery mildew severity of tomato (Solanum lycopersicum L.). The crops were grown during two cropping cycles in protected cultivation. The treatments were: Control (water only); 50 g per plant of EM Bokashi compost in two applications; Penergetic at 1.5 g L−1 applied to the substrate before planting or sprayed on the plants 14 days after transplanting; and BM at 2.5%, 5.0%, 7.5%, and 10% concentrations (vol/vol) in water, via fertigation. Fruit production and quality were assessed. The effects of treatments on powdery mildew (Leveillula taurica Lév. G. Arnaud) were analyzed by using a diagrammatic scale. Bokashi, 10% BM, and Penergetic increased fruit production of the first three fruit trusses. Bokashi treatment increased tomato fruit diameter. The effects on fruit length and total soluble solids varied with each crop cycle. Powdery mildew severity increased with 10% BM, compared to the control. Both 10% BM and Penergetic presented similar fruit production to Bokashi and are good candidates as substitutes for Bokashi as organic fertilizers/amendments while maintaining tomato yield.