Phytoparasitica最新文献

The sorghum aphid Melanaphis sorghi (Theobald, 1904) is the most critical pest in sorghum crops grown in the USA and Mexico. The cultivated area of sorghum was reduced by more than 30% between 2016 and 2019 in northern Mexico, Guanajuato, Morelos, and other regions. This study provides essential information to support an Integrated Pest Management of this insect. M. sorghi field colonies from Guanajuato, Mexico, were identified by morphometric criteria and reared on Sorghum bicolor var. UPM-219 leaf discs using a bioclimatic chamber under different temperatures: 5, 10, 15, 20, 25, 30, 35 and 40 °C. The highest mortality occurred in extreme temperatures: 40 °C (100%). The lowest temperature assessed (5 °C) shows no reproduction, but the pre-reproductive period spread to 62.5 days, allowing an average of 88.2 days of the insects' survival. At 20 °C, M. sorghi produced a supernumerary N5 stage that prolonged the development by 7.1 days, while at the highest temperature (40 °C), N1s died after 0.9 days. The most prolonged reproductive period was 33.2 days (0.6 nymphs/day) at 10 °C, in contrast to 4.1 days (0.4 nymphs/day) at 35 °C. The most extended post-reproductive period (22.4 days) was observed at 10 °C and the shortest (4.2 days) at 35 °C. The highest fertility average (79.06 nymphs) was reached at 25 °C. The heat units required for each generation were 158.9, while theoretical thermal thresholds were 2.0 and 40 °C. Population parameters show that 25 °C is the optimal temperature for this aphid, estimating Ro (79.06), Rm (0.44), T (10.01), DT (1.59), and λ (1.55).

Achieving durable resistance against wheat rust diseases is a primary goal of many wheat breeding programmes. This study aimed to characterize adult plant rust resistance in some old and new Indian bread-wheat varieties. Sixty-four bread wheat genotypes were evaluated to identify adult plant resistance (APR) to stripe rust and leaf rust during 2016-17 and 2017-18 under controlled environment. In these genotypes, APR was characterized using final disease score (FDS), average coefficient of infection (ACI), and area under disease progress curve (AUDPC). Majority of the genotypes were susceptible to moderately susceptible to stripe rust and moderately resistant to moderately susceptible to leaf rust. Leaf tip necrosis (LTN) and pseudo black chaff (PBC) were present in 41 and 33 genotypes, respectively. The three linked diagnostic molecular markers for APR genes, viz. Yr18/Lr34, Yr46/Lr67 and Lr68 were used to characterize the test genotypes and interestingly, 39 genotypes possessed at least one of the three resistance genes. None of the genotypes carried all the three genes. Lr68 was present in the highest frequency. Pre-green revolution tall Indian bread-wheat varieties, viz. NP101, NP836, NP850, NP856, NP876, and NP880 showed the presence of both Yr46/Lr67 and Lr68, whereas Yr18/Lr34 and Sr2/Yr30 were absent. Post-green revolution semi-dwarf wheats showed new combinations of APR with decreased frequency of Yr46/Lr67 and Lr68 genes. The results of this investigation suggest that the APR genes Yr46/Lr67 and Lr68 do not function additively.

Abstract

Macrolophus pygmaeus (Rambur, 1839) (Hemiptera: Miridae) is a polyphagous predator used in programs of biological control and integrated pest management as a natural enemy against small arthropod pests including whiteflies, thrips, spider mites and aphid. This mirid is also successfully mass reared under factitious prey for commercial purposes. In the present study we assessed and compared the prey consumption, weight gain and conversion efficiency in females of two populations of M. pygmaeus, from mainland Portugal and the Azores, fed on single prey diets of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs, or Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) eggs. We found that female’s prey consumption on eggs of T. absoluta was higher than that of E. kuehniella, presumably due to the comparative size/amount of biomass of the eggs. Translating prey consumption in biomass ingested, we only found a significant difference for consumption on E. kuehniella eggs by M. pygmaeus from the Azores. Despite the smaller size of females from the Azores, they were able to consume more prey and ultimately reaching a similar body weight and conversion efficiency compared with females from mainland, independently of the prey provided. Our results are in line with a previous study, showing differences in the life-history traits of M. pygmaeus from mainland Portugal and Azorean populations fed on alternative prey. From an applied perspective, our results are a contribution to the decision-making on the use of the most effective biocontrol agents for different prey and/or agroecosystem contexts.

The Hawaiian flower thrips, Thrips hawaiiensis (Morgan, 1913) (Thysanoptera: Thripidae) is an important pest of several fruit crops in Türkiye’s Mediterranean region, one of the world’s major citrus-growing regions. In this study, the population fluctuation of T. hawaiiensis and other thrips species was investigated in citrus orchards, weeds, and nearby loquat trees. Results showed significant differences in populations of T. hawaiiensis among citrus varieties. The highest population density and damage ratio of T. hawaiiensis among citrus species were recorded in lemon variety (Kütdiken). Thrips hawaiiensis was detected on Daucus carota L. and Amaranthus albus L. among weeds as well as on flowers of loquat in the sampling area. The life cycle of T. hawaiiensis switched seasonally among citrus, weed, and loquat host plants. In addition, Melanthrips pallidior (Priesner, 1919) was the predominant species on weeds in the sampling area. These data suggest that T. hawaiiensis populations may be affected by climatic variations and hosts in and around the citrus orchard. The results are important in optimizing thrips monitoring and management strategies in citrus.

Abstract

The reciprocal targeting of microRNAs (miRNA) and micro-like-RNAs (milRNA) between hosts and pathogens is critical for understanding their interactions. In this study, reciprocal miRNA targets were explored in two Monilinia fungal pathogens, M. fructicola & M. laxa, and their peach host (Prunus presica). Using in silico analysis, 355 and 266 putative miRNAs were predicted for M. fructicola and M. laxa, respectively. Number of miRNAs and their targets differed based on host and pathogen species as 209 M. fructicola miRNAs target 98 peach genes and 128 M. laxa miRNAs target 338 peach genes. On the other hand, peach miRNAs showed the species-specific responses targeting fungal pathways to struggle with its pathogens. These findings indicate distinct strategies and species-specific interactions in this pathosystem. Besides, through the in vitro experimental designs, 166 and 124 expressed miRNAs by M. fructicola were detected in the host-mimicked and control environments, respectively. Additionally, novel miRNAs were discovered, six of which were in the mimicked environment and the seven in the controlled environment as highlighting dynamic and specialized miRNA expression in M. fructicola depending on the environmental conditions. In conclusion, this study provides the first insights into miRNA-mediated interactions between M. fructicola, M. laxa, and peach hosts. Unrevealing the cross talk through the miRNAs in host–pathogen interactions enhances the understanding of pathogenesis and host defense mechanisms. These findings have implications for disease management strategies and contribute to the fields of basic science and evolutionary biology.

The paper presents all species of Lygus Hahn in Turkey. In this study, a total of 228 Lygus samples collected from Çankırı between 2013–2014 are evaluated. As a result, a total of six species of Lygus are determined from Turkey. In addition, Lygus wagneri ozdikmeni ssp. n., a new subspecies of Lygus wagneri from Çankırı province of Turkey is described. Habitus of holotype (male) and its genitalia are photographed. The newly described subspecies differs significantly from the nominative subspecies of Lygus wagneri and the other closely related Lygus species in terms of genital morphology and external morphology. The distribution data in Turkey and the world of all Lygus species are also given in the text. Accordingly, an identification key for all Lygus species in Turkey is provided.

The Hawaiian flower thrips, Thrips hawaiiensis (Morgan) (Thysanoptera: Thripidae) is an economically important invasive species in citrus grown in the eastern Mediterranean region of Turkey. The diverse impacts of temperature on arthropods are well documented. This study was conducted with the aim of determining the influence of day-degree on insect population dynamics and crop damage levels in Mersin Province, Turkey during 2018–2019. In 2018, the first damage caused by T. hawaiiensis was observed at 300 degree-days (DD), while in 2019, it occurred at 800 DD. The damage percentage was recorded as 28% in the lemon grove, where the population of second instar larvae briefly reached a high level (approximately 2 individuals per fruit). During 2019, the average temperature remained relatively low, and the initial population density of thrips was below the 33-day development threshold (10.4 °C) from January to April. This pattern was observed even during the mild spring season. Additionally, in both sampling locations, the high adult densities, mainly adult females, led to the shedding of a limited number of flowers that had formed in June.

Many plant virus diseases of major economic importance in sub-Saharan Africa are caused by disease complexes resulting from synergistic interaction of two or more viral agents known to enhance disease severity inflicting heavier crop losses. The most destructive of these are maize lethal necrosis disease (MLND), sweet potato virus disease (SPVD), cassava mosaic disease (CMD), cowpea mosaic disease (CPMD), groundnut rosette disease (GRD) and tobacco bushy top disease (TBTD). MLND, SPVD, CMD and CPMD are caused by synergistic interaction of two independent viruses in mixed infection, whereas GRD and TBTD represent helper-dependent synergism in which the multiple agents involved in the disease complexes which include an umbravirus, a polerovirus and a satellite RNA synergistically interact with each other for their survival and spread. Mixed virus infections can cause disease synergism due to viral suppression of RNA silencing of host defense, an increase in viral replication, enhanced viral movement or any combination of these. Each disease complex has its own characteristics, and a variety of factors affecting its epidemiology must be considered when devising diagnostic tools and management options. All the causal viruses are transmitted by insect vectors such as aphids, whiteflies, thrips, or beetles while some are transmitted by seeds or vegetative propagation. Although the diagnosis of the multiple agents is more complicated than those with single infections, multiplex methods primarily based on serology, PCR and next generation sequencing are available and widely used. This paper briefly addresses the etiology, symptoms, economic importance, synergistic mechanisms, diagnosis, field spread and management practices of these disease complexes and discusses future research needs.

Abstract

A study was conducted to investigate the development and fitness of predatory syrphid, Ischiodon scutellaris on cowpea aphid host parasitised by Lysiphlebus fabarum. Number of eggs laid by I. scutellaris in the cowpea plants infested with healthy aphids (317.16 ± 14.84 eggs) and in plants with mixed population of healthy and parasitised aphids (302.20 ± 5.49 eggs) were statistically on par with each other. The number of healthy aphids (243 ± 36.65 aphids) and mixed population of healthy and parasitised aphids (206.60 ± 37.39 aphids) consumed by I. scutellaris was statistically on par with each other. Net reproductive rate (R₀) of I. scutellaris in the healthy and healthy + mummified aphid hosts were 289.90 ± 7.66 and 267.40 ± 2.74, respectively. The intrinsic rate of increase (r) of I. scutellaris on the healthy (0.15 ± 0.08) and healthy + mummified aphid hosts (0.14 ± 0.07) was significantly different from each other. The results of the study confirmed that adult flies of I. scutellaris could be maintained in the mixed population of healthy and mummified aphid host, A. craccivora without any interference in its oviposition and egg hatchability. The observations of this study are of practical significance in terms of culture maintenance of syrphid predator, I. scutellaris at times of non-availability of pure healthy aphid hosts.

This is the first record of Exorista deligata (Pandellé, 1896) (Diptera: Tachinidae) as a parasitoid of Hyposidra talaca (Walker, 1860) (Lepidoptera: Geometridae) from India. H. talaca is a major and new emerging defoliator of the Tea plant Camellia sinensis (L) Kuntze (Theaceae). It completes multiple generations per year without diapause on C. sinensis, resulting in heavy crop loss. The field-collected larvae/pupa of H. talaca were checked for parasitoid infestations and reared until either the host or parasitoid emerged. The parasitoid was identified as E. deligata with morphological characteristics and confirmed by the mitochondrial cytochrome oxidase subunit-I (COX-CO1) gene sequencing technique. The parasitoid is infrequent with unexplored parasitic biology. It parasitises the larva and completes its lifecycle inside the developing H. talaca by entirely devouring the host. The mean percent parasitisation caused by E. deligata studied herein was 25.4% (range 5.88%-57.69%). Based on its parasitisation ability, we suggest the species could be a potential biological control agent to address the damage mitigation caused by the tea looper pest, H. talaca.

Graphical abstract