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Plant diseases have a direct impact on agricultural food production. The time required to detect the pathogen plays a crucial role to minimize the fungal-induced disease damage in crops. Current microbial detection techniques take several days to identify the disease. Microwave detection techniques have proven to be a good candidate in identifying pathogens. Microwave dielectric characterization based on an open-ended coax technique is proposed to electrically characterize pathogens having potential applications in plant diseases. Seven common fungi growing on major crops in the United Arab Emirates were isolated and cultured in the lab. A microwave dielectric assessment kit, based on the open-ended coax technology, was used to obtain the dielectric properties of samples. Our data demonstrated a distinct variability between soil- and air-borne pathogenic fungi. Thus, individual fungi can be identified based on their specific microwave dielectric signature. Factors such as conidial sporulation and hyphal growth and polarization of these fungi may attribute to these electric discrepancies. Dielectric spectroscopy modeling based on the Havriliak–Negami model was used to help to understand the molecular structure interaction with the high-frequency signal. This paper revealed a significant dielectric contrast behavior variation among all seven fungi. This paper also supported previous results obtained by other researchers, which classified fungi into two main groups, namely hydrophilic and hydrophobic. Nonetheless, the fungus Alternaria solani has different behavior from this classification. This research is the first to demonstrate the ability of dielectric microwave characterizations tests to facilitate rapid diagnosis and appropriate treatments of plant diseases.

In the United Arab Emirates (UAE), royal poinciana (Delonix regia) trees suffer from stem canker disease. Symptoms of stem canker can be characterized by branch and leaf dryness, bark lesions, discoloration of xylem tissues, longitudinal wood necrosis and extensive gumming. General dieback signs were also observed leading to complete defoliation of leaves and ultimately death of trees in advanced stages. The fungus, Neoscytalidium dimidiatum DSM 109897, was consistently recovered from diseased royal poinciana tissues, this was confirmed by the molecular, structural and morphological studies. Phylogenetic analyses of the translation elongation factor 1-a (TEF1-&alpha, ) of N. dimidiatum from the UAE with reference specimens of Botryosphaeriaceae family validated the identity of the pathogen. To manage the disease, the chemical fungicides, Protifert&reg, Cidely&reg, Top and Amistrar&reg, Top, significantly inhibited mycelial growth and reduced conidial numbers of N. dimidiatum in laboratory and greenhouse experiments. The described &ldquo, apple bioassay&rdquo, is an innovative approach that can be useful when performing fungicide treatment studies. Under field conditions, Cidely&reg, Top proved to be the most effective fungicide against N. dimidiatum among all tested treatments. Our data suggest that the causal agent of stem canker disease on royal poinciana in the UAE is N. dimidiatum.

Date palm (Phoenix dactylifera L.) is one of the most important plants grown for its edible fruit. Palm diseases are among the major factors affecting its growth and productivity. In the United Arab Emirates (UAE), the causal agent of black scorch on date palm was found to be Thielaviopsis punctulata. The pathogen was isolated from all tissues of diseased trees affected by the virulent T. punctulata. Depending on the severity of the infection, symptoms included tissue necrosis, wilting, neck bending, death of terminal buds, and eventual plant mortality. This fungus, which was consistently isolated on potato dextrose agar from infected tissues, produced two types of conidia: the thick-walled aleuroconidia (chlamydospores) and phialoconidia (endoconidia). In addition, all target regions of 5.8S ribosomal RNA, 28S ribosomal DNA, β-tubulin, and transcription elongation factor 1-α genes of the pathogen were amplified using polymerase chain reaction. We also found that the fungicide Score inhibited the mycelial growth of T. punctulata both in vitro and in vivo. Altogether, the morphology of the fruiting structures, pathogenicity tests, and molecular identification confirmed that the causal agent of symptomatic tissues is T. punctulata. This is the first report of the black scorch disease and the fungus T. punctulata on date palm in the UAE.

Mango is affected by different decline disorders causing significant losses to mango growers. In the United Arab Emirates (UAE), the pathogen was isolated from all tissues sampled from diseased trees affected by Lasiodiplodia theobromae. Symptoms at early stages of the disease included general wilting appearance of mango trees, and dieback of twigs. In advanced stages, the disease symptoms were also characterized by the curling and drying of leaves, leading to complete defoliation of the tree and discolouration of vascular regions of the stems and branches. To substantially reduce the devastating impact of dieback disease on mango, the fungus was first identified based on its morphological and cultural characteristics. Target regions of 5.8S rRNA (ITS) and elongation factor 1-α (EF1-α) genes of the pathogen were amplified and sequenced. We also found that the systemic chemical fungicides, Score®, Cidely® Top, and Penthiopyrad®, significantly inhibited the mycelial growth of L. theobromae both in vitro and in the greenhouse. Cidely® Top proved to be a highly effective fungicide against L. theobromae dieback disease also under field conditions. Altogether, the morphology of the fruiting structures, molecular identification and pathogenicity tests confirm that the causal agent of the mango dieback disease in the UAE is L. theobromae.

Many fungal diseases affect date palm causing considerable losses in date production worldwide. We found that the fungicide Cidely® Top inhibited the mycelial growth of the soil-borne pathogenic fungus Thielaviopsis punctulata, the causal agent of black scorch disease of date palm, both in vitro and in vivo. Because the use of biocontrol agents (BCAs) can minimize the impact of pathogen control on economic and environmental concerns related to chemical control, we aimed at testing local actinomycete strains isolated from the rhizosphere soil of healthy date palm cultivated in the United Arab Emirates (UAE) against T. punctulata. The selected isolate can thus be used as a potential agent for integrated disease management programs. In general, the BCA showed antagonism in vitro and in greenhouse experiments against this pathogen. The most promising actinomycete isolate screened showed the highest efficacy against the black scorch disease when applied before or at the same time of inoculation with T. punctulata, compared with BCA or fungicide application after inoculation. The nucleotide sequence and phylogenetic analyses using the 16S ribosomal RNA gene with other Streptomyces spp. in addition to morphological and cultural characteristics revealed that the isolated UAE strain belongs to Streptomyces globosus UAE1. The antagonistic activity of S. globosus against T. punctulata, was associated with the production by this strain of diffusible antifungal metabolites i.e., metabolites that can inhibit mycelial growth of the pathogen. This was evident in the responses of the vegetative growth of pure cultures of the pathogen when exposed to the culture filtrates of the BCA. Altogether, the pathogenicity tests, disease severity indices and mode of action tests confirmed that the BCA was not only capable of suppressing black scorch disease symptoms, but also could prevent the spread of the pathogen, as a potential practical method to improve disease management in the palm plantations. This is the first report of an actinomycete, naturally occurring in the UAE with the potential for use as a BCA in the management of the black scorch disease of date palms in the region.

Date palm orchards suffer from serious diseases, including sudden decline syndrome (SDS). External symptoms were characterized by whitening on one side of the rachis, progressing from the base to the apex of the leaf until the whole leaf dies, while the internal disease symptoms included reddish roots and highly colored vascular bundles causing wilting and death of the tree. Although three Fusarium spp. (F. oxysporum, F. proliferatum and F. solani) were isolated from diseased root samples, the fungal pathogen F. solani was associated with SDS on date palm in the United Arab Emirates (UAE). Fusarium spp. were identified based on their cultural and morphological characteristics. The internal transcribed spacer regions and large subunit of the ribosomal RNA (ITS/LSU rRNA) gene complex of the pathogens was further sequenced. Pathogenicity assays and disease severity indices confirm the main causal agent of SDS on date palm in the UAE is F. solani. Application of Cidely&reg, Top (difenoconazole and cyflufenamid) significantly inhibited the fungal mycelial growth in vitro and reduced SDS development on date palm seedlings pre-inoculated with F. solani under greenhouse conditions. This is the first report confirming that the chemical fungicide Cidely&reg, Top is strongly effective against SDS on date palm.