ABSTRACT
A double-stranded RNA (dsRNA) of approximately 16 kbp was isolated from symptomless common buckwheat (Fagopyrum esculentum) plants. The size of the dsRNA suggested that it was the replicative form of an endornavirus. The dsRNA was sequenced, and it consisted of 15,677 nt, containing a single open reading frame that potentially encoded a polyprotein of 5190 aa. The polyprotein contained conserved domains for a viral methyltransferase, viral RNA helicase 1, MSCRAMM family adhesion SdrC, UDP-glycosyltransferase, and viral RNA-dependent RNA polymerase 2. A site-specific nick in the plus strand was detected near the 5' end of the dsRNA. BLASTp analysis showed that the polyprotein shared the highest identity with the polyprotein of winged bean endornavirus 1. Results of phylogenetic analysis supported placing this novel virus from common buckwheat, which was provisionally named "Fagopyrum esculentum endornavirus 1", in the genus Alphaendornavirus of the family Endornaviridae.
Subject(s)
Fagopyrum , RNA Viruses , Base Sequence , Fagopyrum/genetics , Genome, Viral , Open Reading Frames , Phylogeny , Plant Diseases , RNA Viruses/genetics , RNA, Double-Stranded/genetics , Sequence Analysis, DNA , Viral Proteins/geneticsABSTRACT
New succinate dehydrogenase inhibitor fungicides (SDHIs), isopyrazam, pyraziflumid and isofetamid were introduced in the Japanese market in 2017-2018 to control powdery mildew on cucumber. SDHI resistance of the disease fungus (Podosphaera xanthii) was first reported during 2008-2009 against boscalid. Then, penthiopyrad which belongs to SDHIs was introduced in 2010, but subsequent monitoring study was not performed. We investigated the sensitivity of P. xanthii field isolates from Ibaraki Prefecture, Japan, to SDHIs and SdhB, SdhC and SdhD gene mutations, using a leaf disc assay and SDH gene analysis. A total of 19 out of the 22 selected isolates showed resistance to SDHIs. The 19 isolates were phenotypically categorized into three types: Resistant I as moderately and Resistant II as highly resistant to penthiopyrad, isopyrazam and pyraziflumid but sensitive to isofetamid and Resistant III as highly resistant to isofetamid but sensitive to the other three SDHIs. SDH gene analysis revealed that Resistant I and III isolates carried a substitution in PxD-S121P and PxC-A86V, respectively. Resistant II carried three different substitutions: PxC-G151R, PxC-G172D, and PxD-H137R. Among 127 isolates sampled from 16 cucumber greenhouses, 54 exhibited Resistant I phenotype and carried only PxD-S121P. Fifty-six isolates exhibited Resistant II and carried PxC-G151R (four isolates), PxC-G172D (24), and PxD-H137R (28). Only two isolates expressed the Resistant III phenotype carrying PxC-A86V. To the best of our knowledge, this is the first report demonstrating cross-resistance patterns and the molecular characterization of SDHIs in P. xanthii.
Subject(s)
Cucumis sativus , Succinate Dehydrogenase , Drug Resistance, Fungal , Japan , Plant DiseasesABSTRACT
Nesidiocoris tenuis is a zoophytophagous mirid bug widely studied for its role in preying on major greenhouse pests. Since N. tenuis has now been known for its vigorous predation potential on pests such as Bemisia tabaci, many applied entomologists are now recommending that N. tenuis be merged into the Integrated Pest management (IPM) systems. However, successful integration of N. tenuis into any IPM system depends on thorough evaluation with compatible pesticides, as incompatible pesticides can offset the whole idea of IPM. Here, we simulate the field situation where N. tenuis feeds directly on a contaminated B. tabaci nymph or leaves. However, instead of using live B. tabaci nymphs, we used brine shrimp eggs, Artemia salina (Linnaeus, 1758). Brine shrimp eggs have been reported to be an excellent factitious supplementary diet in augmenting N. tenuis populations. Thus, we use brine shrimp eggs to determine the toxicity of pesticides, to which the calculated mortality rates can be used to determine which pesticides can be used together with N. tenuis in an IPM system against any related pest.â¢We developed a customized containment system that promotes aeration and minimize contamination.â¢Pesticide contaminated hatched brine shrimp eggs is delivered to N. tenuis in the aerated containment system.â¢In addition to established methods such as leaf dipping or insect dipping, this method shows to mimic N. tenuis feeding on contaminated B. tabaci nymphs in field conditions thus, predicts how a pesticide may be of toxic or compatible with N. tenuis when both are integrated together.
ABSTRACT
Natural predators such as Nesidiocoris tenuis are known for their role in managing greenhouse pests. However, techniques in maximizing the biological control potential of N. tenuis under field conditions are still lacking. We evaluated under greenhouse conditions the prospects of Artemia cysts enhanced with high fructose corn syrup and honey, and delivered using hemp strings (hemp rope) as supplementary factitious dietary in augmenting the proliferation and spread of N. tenuis on tomato plants. Results showed that N. tenuis supplemented with hemp rope could establish, proliferate and disperse among tomato plants compared to the N. tenuis supplemented with banker plants. Even though N. tenuis proliferated exponentially on banker plants, their movement and relocation to tomato plants, as expected, were only congested on tomato plants near the banker plants. However, as the survey continued, they relocated to the rest of the tomato plants. Furthermore, the number of Bemisia tabaci eggs and nymphs, a serious greenhouse pest of tomato, was observed to be significantly reduced in hemp rope greenhouse compared to banker plants and the negative control (no pest control system) greenhouses. This study, therefore, establishes foundational data on the usage of Artemia cysts enhanced with isomerized sugar (high fructose corn syrup) and honey under greenhouse conditions as factitious supplementary dietary in supporting N. tenuis establishment and spread, traits that are essential towards development of whitefly Integrated Pest Management (IPM) system. enhanced with isomerized sugar (high fructose corn syrup) and honey.
ABSTRACT
BACKGROUND: Bemisia tabaci is a notorious agricultural pest that causes serious damage to many crops via herbivory and spread of viral diseases. Effective control measures are, therefore, required. Integrating entomopathogenic fungi into the chemical control system offers promise for B. tabaci management. RESULTS: In-vitro assays on the augmentative effect of Beauveria bassiana GHA strain with insecticides, and its compatibility with fungicides were tested. Varying egg mortality was observed for most insecticides except for milbemectin. Pyrifluquinazon was less effective against the nymphs. Flonicamid showed no insecticidal effect on either nymphs or adults. However, increased mortality in nymphs and adults was observed when flonicamid was mixed with Beauveria bassiana GHA strain. Furthermore, no significant synergistic effect of mixing pesticides with B. bassiana GHA strain was observed. Most insecticides (when not mixed with B. bassiana) showed high (>80%) mortality against B. tabaci nymphs and adults. Most fungicides tested showed no inhibitory effects on B. bassiana GHA strain against B. tabaci nymphs and adults. Fungistatic effect was observed in the mycelial and spore germination inhibition studies. Weekly rotation of some pesticides with B. bassiana GHA strain in greenhouse conditions yielded significant reduction in different growth stages of B. tabaci. However, no significant difference in viral incidence was observed. CONCLUSION: Laboratory and field tests showed positive effects of augmenting pesticides and B. bassiana GHA strain against B. tabaci nymphs and adults. Therefore, augmentation of pesticides and B. bassiana GHA strain is one prospect towards developing an effective B. tabaci IPM system. © 2020 Society of Chemical Industry.