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Effects of Wheat Diseases on Yield Generation and Quality In this special issue,Simón et al.reviewed the impact of nitrogen fertilization and fungicides on the severity of foliar diseases and their effects on biomass accumulation, grain yield, milling, and end-use quality, as affected by the bread-making characteristics of the wheat genotypes and the nutritional requirements of the pathogen involved. Total antioxidant activity, flavonoid, and carotenoid concentrations significantly decreased under increasing blast severity. [...]grain K and total phenolic concentration were augmented at a certain level of severity and then reduced, whereas some other biochemical traits increased or decreased. Furthermore, the study of the variability and changes in pathogen populations is a pre-requisite for releasing cultivars with gene combinations that adequately control the predominant pathotypes. In this special issue,Mohammadi et al.showed the significant biological function of the ZtR1m1 gene, encoding a MADS-box transcription factor in the last stage of infection of Zymoseptoria tritici P. Crous, the causal agent of Septoria leaf blotch, indicating that ZtR1m1 affects penetration, colonization, fungal biomass production, pycnidial formation, differentiation, and melanization required for fruiting body formation.

Key messageQTLs for insect resistance parameters, trichome type IV development, and more than 200 non-volatile metabolites, including 76 acyl sugars, all co-locate at the end of Chromosome 2 of Solanum galapagense.Host plant resistance is gaining importance as more and more insecticides are being banned due to environmental concerns. In tomato, resistance towards insects is found in wild relatives and has been attributed to the presence of glandular trichomes and their specific phytochemical composition. In this paper, we describe the results from a large-scale QTL mapping of data from whitefly resistance tests, trichome phenotyping and a comprehensive metabolomics analysis in a recombinant inbred line population derived from a cross between the cultivated Solanum lycopersicum and the wild relative S. galapagense, which is resistant to a range of pest insects. One major QTL (Wf-1) was found to govern the resistance against two different whitefly species. This QTL co-localizes with QTLs for the presence of trichomes type IV and V, as well as all 76 acyl sugars detected and about 150 other non-volatile phytochemicals, including methyl esters of the flavonols myricetin and quercetin. Based on these results, we hypothesize that Wf-1 is regulating the formation of glandular trichome type IV on the leaf epidermis, enabling the production and accumulation of bioactive metabolites in this type of trichomes.

The evolution of cocoa farming was quickly confronted with the development of pests and diseases. These sanitary constraints have shaped the geographical distribution of production over the centuries. Current climate change adds an additional constraint to the plant health constraints, making the future of cocoa farming more uncertain. Climate change is not only affecting the areas where cocoa is grown for physiological reasons, particularly in relation to changes in water regimes, but also affects the distribution of pests and diseases affecting this crop. These different points are discussed in the light of the trajectories observed in the different cocoa-growing areas. The breeding programs of cocoa trees for sustainable resistance to plant health constraints and climate change are therefore particularly important challenges for cocoa farming, with the other management practices of plantations.

Fusarium wilt disease presents a substantial challenge to tomato production, especially in an open field environment. The peroxidase (POD) activity and total phenolic compounds (TPCs) play a crucial role in measuring the antioxidant capacity of plants. Understanding the variations in the POD and TPC levels during disease-induced stress becomes important for effectively managing Fusarium wilt and enhancing tomato production. This study investigates the impacts of Trichoderma harzianum inoculation through the root drip method on five tomato cultivars. It compares these cultivars to their non-treated counterparts when they are subjected to infection by Fusarium oxysporum f. sp. lycopersici (Fol). The results showed that the level of resistance to Fol is based on the specific tomato cultivar. Notably, 'MT26' exhibited the lowest disease severity index (DSI), indicating a strong response, whereas 'CLN3682F' showed notable susceptibility. Regarding the POD and TPC activity, its exhibition differed in compatibility with the response of each tomato cultivar to Fusarium wilt disease. The resistant cultivars increased the POD activity after the Trichoderma induction before the Fol inoculation, and this activity was further boosted when exposed to disease conditions. Consequently, enhancing the POD and TPC levels during the initial stages could potentially serve as a systemic defence mechanism of tomatoes against the Fusarium wilt disease.

Verticillium (Verticillium dahliae Kleb.) wilt is one of the most devastating diseases affecting olive (Olea europaea L. subsp. europaea var. europaea) cultivation. Its effective control strongly relies on integrated management strategies. Olive cultivation systems are experiencing important changes (e.g., high-density orchards, etc.) aiming at improving productivity. The impact of these changes on soil biology and the incidence/severity of olive pests and diseases has not yet been sufficiently evaluated. A comprehensive understanding of the biology of the pathogen and its populations, the epidemiological factors contributing to exacerbating the disease, the underlying mechanisms of tolerance/resistance, and the involvement of the olive-associated microbiota in the tree’s health is needed. This knowledge will be instrumental to developing more effective control measures to confront the disease in regions where the pathogen is present, or to exclude it from V. dahliae-free areas. This review compiles the most recent advances achieved to understand the olive–V. dahliae interaction as well as measures to control the disease. Aspects such as the molecular basis of the host–pathogen interaction, the identification of new biocontrol agents, the implementation of “-omics” approaches to unravel the basis of disease tolerance, and the utilization of remote sensing technology for the early detection of pathogen attacks are highlighted.

Stem rust, caused by Puccinia graminis f. sp. tritici , is a destructive fungal disease of bread wheat ( Triticum aestivum L.) and poses a major challenge to wheat production in sub-Saharan Africa and Asia. The continuous evolution and variable nature of stem rust predispose wheat to serious genetic vulnerability, necessitating proactive incorporation of new and effective resistance sources into breeding lines. This study evaluated 25 wheat genotypes over three seasons at the Kenya Agricultural and Livestock Research Organization (KALRO), Njoro, to assess resistance mechanisms and yield stability under stem rust pressure. A 5 × 5 partially balanced alpha lattice design was employed. Disease progression was assessed using final disease severity (FDS) and area under the disease progress curve (AUDPC), alongside evaluations of agronomic performance. Statistical analyses revealed significant ( P ≤ 0.001) effects of genotype, season, and genotype × season interaction for AUDPC and agronomic traits. Grain yield (GY) was significantly ( P ≤ 0.001) negatively correlated with disease components, and positively correlated with kernels per spike (KS), biomass (BM), harvest index (HI), and thousand kernel weight (TKW). Broad-sense heritability (H 2 ) estimates ranged from 59.90% for grain filling period to 95.58% for FDS. Adult plant resistance genes Lr34/Yr18/Sr57 , Lr46/Yr29/Sr58 , Sr2/Yr30 , and Lr67/Yr46/Sr55/Pm46 were detected in various combinations across 21 genotypes. Based on disease response and yield performance, genotypes 8790929, 8790027, 8790948, and 8790935 exhibited the highest levels of resistance and superior grain yield. These genotypes represent valuable sources of stem rust resistance and are recommended for use in breeding programs for gene introgression and varietal development.

Multiple susceptibility genes (S), identified in Arabidopsis, have been shown to be functionally conserved in crop plants. Mutations in these S genes result in resistance to different pathogens, opening a new way to achieve plant disease resistance. The aim of this study was to investigate the role of Defense No Death 1 (DND1) in susceptibility of tomato and potato to late blight (Phytophthora infestans). In Arabidopsis, the dnd1 mutant has broad-spectrum resistance against several fungal, bacterial, and viral pathogens. However this mutation is also associated with a dwarfed phenotype. Using an RNAi approach, we silenced AtDND1 orthologs in potato and tomato. Our results showed that silencing of the DND1 ortholog in both crops resulted in resistance to the pathogenic oomycete P. infestans and to two powdery mildew species, Oidium neolycopersici and Golovinomyces orontii. The resistance to P. infestans in potato was effective to four different isolates although the level of resistance (complete or partial) was dependent on the aggressiveness of the isolate. In tomato, DND1-silenced plants showed a severe dwarf phenotype and autonecrosis, whereas DND1-silenced potato plants were not dwarfed and showed a less pronounced autonecrosis. Our results indicate that S gene function of DND1 is conserved in tomato and potato. We discuss the possibilities of using RNAi silencing or loss-of-function mutations of DND1 orthologs, as well as additional S gene orthologs from Arabidopsis, to breed for resistance to pathogens in crop plants.

Grafting susceptible crop plants on disease and pest-resistant rootstocks is a valuable management practice for reducing damage caused by plant-parasitic nematodes and plant pathogens in vegetable and fruit tree crops worldwide. By combining pedigree-based genetic information with quantitative phenotypic data, it would be easier to identify and select rootstocks with superior trait combinations needed for rootstock development using marker-assisted-selection, enabling rapid selection of successive-generation rootstocks with the desirable trait combinations for development of marketable rootstocks. [...]when a susceptible scion is grafted on a rootstock with low susceptibility, the rootstock susceptibility may be increased. [...]it is important to evaluate each scion/rootstock combination and not rely on rootstock performance alone since there may be unexpected scion/rootstock interactions. Conflict of interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Cucurbit downy mildew, caused by the oomycete Pseudoperonospora cubensis, is a devastating, worldwide-distributed disease of cucurbit crops in the open field and under cover. This review provides recent data on the taxonomy, biology, ecology, host range, geographic distribution and epidemiology of P. cubensis. Special attention is given to host-pathogen interactions between P. cubensis and its economically-important cucurbit hosts (Cucumis sativus, C. melo, Cucurbita pepo, C. maxima, and Citrullus lanatus); pathogenic variability in P. cubensis at the species, genus, and population levels; and, differentiation of pathotypes and races. Genetics and variability of host resistance and cellular and molecular aspects of such resistance are considered. A focus is given to methods of crop protection, including prevention and agrotechnical aspects, breeding for resistance--classical and transgenic approaches, chemical control and fungicide resistance. Novel technologies in biological and integrated control are also discussed. This review also summarizes the most important topics for future research and international collaboration.

Maize is a staple for billions across the globe. However, in tropical and sub-tropical regions, maize is frequently contaminated with aflatoxins by Aspergillus section Flavi fungi. There is an ongoing search for sources of aflatoxin resistance in maize to reduce continuous exposures of human populations to those dangerous mycotoxins. Large variability in susceptibility to aflatoxin contamination exists within maize germplasm. In Mexico, several maize landrace (MLR) accessions possess superior resistance to both Aspergillus infection and aflatoxin contamination but their mechanisms of resistance have not been reported. Influences of kernel integrity on resistance of four resistant and four susceptible MLR accessions were evaluated in laboratory assays. Wounds significantly ( P < 0.05) increased susceptibility to aflatoxin contamination even when kernel viability was unaffected. Treatments supporting greater A. flavus reproduction did not ( P > 0.05) proportionally support higher aflatoxin accumulation suggesting differential influences by some resistance factors between sporulation and aflatoxin biosynthesis. Physical barriers (i.e., wax and cuticle) prevented both aflatoxin accumulation and A. flavus sporulation in a highly resistant MLR accession. In addition, influence of temperature on aflatoxin contamination was evaluated in both viable and non-viable kernels of a resistant and a susceptible MLR accession, and a commercial hybrid. Both temperature and living embryo status influenced ( P < 0.05) resistance to both aflatoxin accumulation and A. flavus sporulation. Lower sporulation on MLR accessions suggests their utilization would result in reduced speed of propagation and associated epidemic increases in disease both in the field and throughout storage. Results from the current study should encourage researchers across the globe to exploit the large potential that MLRs offer to breed for aflatoxin resistant maize. Furthermore, the studies provide support to the importance of resistance based on the living host and maintaining living status to reducing episodes of post-harvest contamination.