Mutations in Sdh Gene Subunits Confer Different Cross Resistance Patterns to SDHI Fungicides in Alternaria alternata Causing Alternaria Leaf Spot of Almond in California

Alternaria leaf spot caused by Alternaria alternata and A. arborescens is a common disease of almond in California. Succinate dehydrogenase inhibitors (SDHIs) are widely used for its management, however, we observed reduced performance of SDHI fungicides at some field sites. Thus, we evaluated the sensitivity of 520 isolates of the main pathogen A. alternata from major production areas collected between 2006 and 2019 to boscalid and of a subset of 204 isolates to six members of the SDHIs belonging to six sub-groups. Additionally, 97 isolates (14 sensitive and 83 with reduced sensitivity) of the 204 were used to determine the molecular mechanisms of resistance. A wide range of in vitro concentrations to effectively inhibit mycelial growth by 50% (EC50 values) was determined for each fungicide using the spiral gradient dilution method. Some isolates were highly resistant (EC50 values >10 μg/ml) to boscalid (a pyridine-carboxamide), pyraziflumid (a pyrazine-carboxamide), and fluxapyroxad (a pyrazole-4-carboxamide), but not to fluopyram (a pyridinyl-ethyl-benzamide), isofetamid (a phenyl-oxo-ethyl thiophene amide), and pydiflumetofen (a N-methoxy-(phenyl-ethyl)-pyrazole-carboxamide). There was no strong cross resistance among the fungicides tested, including for the two pyrazole-4-carboxamides fluxapyroxad and penthiopyrad (tested for 33 of the 204 isolates). The comparison of EC50 values for fluopyram and isofetamid resulted in the highest coefficient of determination (R2 = 0.582) among ten pairwise comparisons between sub-groups. Sequence analyses of the 97 isolates revealed five mutations in SdhB, SdhC, or SdhD subunits of the Sdh target gene among 73 isolates with reduced sensitivity to at least one SDHI. No mutations were detected in the 14 sensitive isolates and in 10 of the 83 isolates with reduced sensitivity. The most common mutation (59 isolates) was H134R in SdhC. Other mutations included H277Y (8 isolates) and H277L (2 isolates) in SdhB, as well as G79R (2 isolates) and S135R (2 isolates) in SdhC. Mutations H277Y in SdhB and S135R in SdhC were only present in isolates collected in 2012 or earlier. Both conferred mostly high levels of resistance to boscalid and also reduced sensitivity to pyraziflumid, fluxapyroxad, and isofetamid with intermediate EC50 levels. Mutations H277L in SdhB, as well as H134R and G79R in SdhC, that were found in isolates obtained after 2012 had very similar resistance phenotypes with different levels of resistance to boscalid, pyraziflumid, and fluxapyroxad, whereas sensitivity to fluopyram, isofetamid, and pydiflumetofen was mostly less affected. Our data for SDHI fungicides do not support the classical concept of positive cross resistance within a single mode of action. Because some mutations conferred resistance to multiple SDHI sub-groups, however, resistance management needs to consider all SDHIs as a homogenous group that should be mixed or rotated with other modes of action prior to resistance development to either mode of action.

Abnormal sperm morphology is associated with sensitization to inhaled allergens

Background: Allergy is associated with the loss of tolerance of environmental antigens, combined with a pathological immune response. There were no studies up to date that would show whether the quality of semen decreases in people with allergic diseases. Material and methods: The research included men who reported to the Gynecological Outpatient Clinic due to reproductive difficulties, defined as the lack of pregnancy after one year of regular intercourse. Semen quality was assessed according to the World Health Organization (WHO) standard. All patients underwent skin prick tests with the most important inhalation allergens (such as hazel, silver birch, mugwort, rye, dog, cat, Dermatophagoides farinae, Dermatophagoides pteronyssinus, alder, Alternaria alternata, Cladosporium herbarum, and grass mix). The data was statistically analyzed. Results: Results of 52 patients aged 25–52 years (34.62 ± 4.96) were analyzed. The mean BMI (Body mass index) was 28.25 (+ −3.77). It was found that 38 men (73%) had increased body weight, and 14 men (26.9%) were obese (BMI > = 30). 13 patients were smokers (25%), and 24 patients (46%) had skin tests positive for at least one inhaled allergen. Sperm tail defects were statistically more significant in patients allergic to birch, rye, cat, alder, and grass. In patients allergic to Alternaria alternata, head defects were statistically more significant ( p < .05). No association was found between allergy to house dust mites, mugwort, hazel, and dogs and the deterioration of semen. Conclusion: Allergy due to inhalation allergens had an influence on the quality of male semen. Further research is necessary to establish the immunological bases of this phenomenon.

First report of Alternaria alternata causing the golden spot in xoconostle (Opuntia matudae) in Hidalgo, México

The species<em> Opuntia ficus-indica</em> is affected by pests and diseases, one of the most important of these being golden spot. The latter has been reported in various countries, including Mexico. Symptoms similar to those of golden spot in <em>O. ficus-indica</em> have been observed in the xoconostle crop (<em>Opuntia matudae</em> Scheinvar, cv. Rosa). The objective of this study was to isolate and identify the causative agent that causes the symptoms, which resembled those of the disease described as golden spot in <em>O. ficus-indica</em>. Simple random sampling in the field (10 plots) was carried out on xoconostle plants that presented the described symptoms. Slices of diseased plant tissue were cut and placed in Petri plates with PDA medium. Compliance with Koch’s postulates showed that the isolated (one aislated) of <em>Alternaria</em> sp. obtained from the field samples colonized the cladodes after inoculations in the greenhouse. Through taxonomic keys, <em>Alternaria</em> sp. was identified as the causative microorganism. Molecular characterization of the isolated <em>Alternaria</em> sp. was identified as <em>Alternaria</em> <em>alternata</em>. This is the first report worldwide of <em>Alternaria alternata</em> as the causal agent of golden spot in a xoconostle crop.

Metabolic regulation by prostaglandin E 2 impairs lung group 2 innate lymphoid cell responses

Background: Group 2 innate lymphoid cells (ILC2s) play a critical role in asthma pathogenesis. Non-steroidal anti-inflammatory drug (NSAID)-exacerbated respiratory disease (NERD) is associated with reduced signaling via EP2, a receptor for prostaglandin E (PGE ). However, the respective roles for the PGE receptors EP2 and EP4 (both share same downstream signaling) in the regulation of lung ILC2 responses has yet been deciphered. Methods: The roles of PGE receptors EP2 and EP4 on ILC2-mediated lung inflammation were investigated using genetically modified mouse lines and pharmacological approaches in IL-33- and Alternaria alternata (A.A.)-induced lung allergy models. The effects of PGE receptors and downstream signals on ILC2 metabolic activation and effector function were examined using in vitro cell cultures. Results: Deficiency of EP2 rather than EP4 augments IL-33-induced lung ILC2 responses and eosinophilic inflammation in vivo. In contrast, exogenous agonism of EP4 but not EP2 markedly restricts IL-33- and Alternaria alternata-induced lung ILC2 responses and eosinophilic inflammation. Mechanistically, PGE directly suppresses IL-33-dependent ILC2 activation through the EP2/EP4-cAMP pathway, which downregulates STAT5 and MYC pathway gene expression and ILC2 energy metabolism. Blocking glycolysis diminishes IL-33-dependent ILC2 responses in mice lacking endogenous PG synthesis but not in PG-competent mice. Conclusion: We have defined a mechanism for optimal suppression of lung ILC2 responses by endogenous PGE -EP2 signaling which underpins the clinical findings of defective EP2 signaling in patients with NERD. Our findings also indicate that exogenously targeting the PGE -EP4-cAMP and energy metabolic pathways may provide novel opportunities for treating ILC2-initiated lung inflammation in asthma and NERD.

Alternaria alternata as a Seed-Transmitted Pathogen of Sida hermaphrodita (Malvaceae) and Its Suppression by Aureobasidium pullulans

Background: Sida hermaphrodita (Virginia fanpetals) was introduced to Poland nearly 70 years ago as a potential fodder plant, and it is gaining importance as an energy crop. Alternaria alternata transmitted by seeds may exert a negative effect on the health of Virginia fanpetals plants. Methods: The virulence of the A. alternata pathogen, isolated from Virginia fanpetals seeds, was tested on detached leaves of Virginia fanpetals plants. The isolates were identified as A. alternata based on partial sequence analysis of Alta1, TEF1a and gdp genes and the ITS 1–5.8SrDNA–ITS 2 region. Pathogen transmission from seeds to seedlings and the influence of seed dressing with a suspension of Aureobasidium pullulans on seedling health were analyzed in a greenhouse experiment. Results: Three of the nine analyzed A. alternata isolates were highly pathogenic for S. hermaphrodita. The initial symptoms of leaf infection were small, round dark brown or black spots which grew into larger dark brown spots surrounded by a chlorotic halo. Alternaria alternata was re-isolated from inoculated plants and was identified as the causal agent of Alternaria leaf spot disease. In the greenhouse experiment, S. hermaphrodita seeds dressed with a suspension of A. pullulans and inoculated with A. alternata produced a higher number of seedlings with a higher health status than non-dressed seeds. Conclusions: The study demonstrated that A. alternata is transmitted from infected S. hermaphrodita seeds to developing plants and biological control limits this phenomenon.