Deladenus taedae n. sp. was isolated from loblolly pine wood (Pinus taeda) intercepted in Ningbo, P.R. China, in imports from the USA. This new species is morphologically described and illustrated and characterised molecularly. Both mycetophagous and infective forms were recovered and described. The new species, D. taedae n. sp., resembles some other species of Deladenus in which the excretory pore is situated anterior to the hemizonid. The new species is characterised by the lateral fields with six lines, pointed tail ending and small spermatheca in mycetophagous females and short stylet in infective females. In mycetophagous females, the excretory pore is 74-98 μm from the anterior end and 37-54 μm anterior to the hemizonid. The partial rDNA 18S, complete internal transcribed spacer, 5.8S and partial 28S D2/D3 genes were amplified and sequenced. Phylogenetic analyses of the genes distinguished this new species from all other sequenced Deladenus species.
Soil nematode communities are one of the most used bioindicators for assessing soil health and soil conditions. However, they are dependent on the presence of plants, some of which, known as ‘invasive’, affect local biodiversity when established. This study aimed to compare the communities of soil nematodes in riverbanks non-invaded and invaded by Fallopia japonica at three sites characterised by different environmental conditions. Our findings indicated that the ecosystem had a larger impact on the nematode communities than did the environmental variability at the study sites. Soil properties, such as pH, moisture content and organic-carbon content, differed significantly amongst the sites, but the nematode communities remained similar. Organic-carbon content was lower, and soil pH was higher, in the ecosystem with invasive F. japonica. Total nematode abundance, the abundances of fungivores, herbivores, omnivores and predators, and the maturity indices were significantly lower with invasive F. japonica. Fungivorous nematodes are essential for breaking down organic matter and releasing nutrients. Herbivorous nematodes respond to changes in the vegetation, and omnivorous and predatory nematodes contribute to the overall biodiversity and ecological balance in the soil ecosystem, so their lower abundance suggests a disturbance in the soil food web. The lower maturity indices suggested a disturbance or degradation of the soil ecosystem, which could have secondary negative effects on plant growth, nutrient availability and ecosystem resilience. These findings indicate that invasion both decreased the abundance of important soil organisms and disrupted the cycling of nutrients, potentially leading to long-term negative consequences for the invaded ecosystems. Understanding and managing the effects of invasive plants such as F. japonica are crucial for preserving soil health and promoting sustainable ecosystem functioning.
This paper presents the first comprehensive detailed transmission electron microscope observations of sperm development and structure of a plectid nematode. Sperm development of Anaplectus granulosus resembles that of nematodes of the order Rhabditida, known as the rhabditid pattern of spermatogenesis. It includes formation of complexes of fibrous bodies (FB) with membranous organelles (MO), which appear in spermatocytes; the complexes dissociate in the spermatids. The mature spermatozoa are bipolar cells subdivided into a pseudopod and a main cell body containing a nucleus with nine singlet centrioles, peripheral mitochondria and MOs. However, the development and structure of sperm in A. granulosus deviates remarkably from the common rhabditid pattern by an unusual early transformation of FBs into large amorphous masses in the spermatids; the subsequent formation of a concentric structure of immature spermatozoa with a predominant amorphous mass around the central nucleus and thin peripheral cytoplasm with organelles (MOs and mitochondria); and by the transformation of MO in mature spermatozoa into simple cisterns. Thus, the pattern of spermatogenesis of A. granulosus supports the close relations of Plectida and Rhabditida, but specific peculiarities of the sperm development delineate Plectida from Rhabditida and other orders.
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Aphelenchoides besseyi is among the most devastating plant-parasitic nematodes and causes severe loss, mainly on japonica rice in China. Recently the nematode has been found to be present in the seeds of indica rice and the hybrid rice cultivars also show symptoms of the nematode damage. To understand the variations in different rice cultivars against A. besseyi, the dynamics of nematode population, the incidence of symptoms and the effects on plant yield were investigated in field experiments during 2017-2018 by inoculation of mixed stages of A. besseyi onto the seeds and seedlings of different types of rice cultivars. The results showed few nematodes could be recovered from the plants at the seedling and the end of tillering stages in all the cultivars. After flowering, the number of nematodes per panicle increased and the highest number was found in ‘Zheyou 18’ in 2017 (1050.2) and 2018 (732.1). The average incidence of the inoculated plants showing white-tip symptoms ranged from 0.5 to 10.3% and from 0.0 to 75.7% at the tillering stage in 2017 and 2018, respectively. The incidences of white-tip symptoms in the indica cultivars, including ‘9311’, ‘Minghui 63’ and ‘Nei 5 you 39’, were significantly lower than in ‘Xingxiang’, a japonica cultivar and ‘Zheyou 18’, a hybrid rice cultivar, both at the flowering stage in 2017 and at the end of the tillering stage in 2018. A strong interaction of the treatments and cultivars on the 1000-grain weight and panicle length was evident.
The legume cavalcade, Centrosema pascuorum, is used extensively as a cover crop and as a component of conservation agriculture systems. It is also an attractive rotation or cover crop for the management of root-knot nematodes (RKN; Meloidogyne spp.) as it is a non-host. RKN are persistent pests that are well known to be difficult to control. However, the mechanisms governing the non-host status of cavalcade is unknown. The current study established that cavalcade leaves are toxic to RKN as either aqueous extracts or soil amendments. Bioassays conducted using Meloidogyne javanica showed that a 90% concentration of aqueous extract derived from 1-month-old cavalcade leaves (89 mg crude extract ml−1) suppressed nematode hatch (82.9%) and killed infective second-stage juveniles of M. javanica (85.3%). Soil amendments with 1% (w/w) of 1-month-old cavalcade leaves (0.99 mg crude extract g−1 soil) also provided effective control of M. javanica in the glasshouse on okra. One-month-old leaves appeared more effective than 2- or 3-month-old leaves. The soil amendments had no adverse phytotoxic effect on okra seed germination. Our study demonstrates the potential for using cavalcade leaves or extracts to manage RKN. This may be due to the nematicidal activity of the various compounds in the leaves, such as flavonoids, phenols and terpenoids, which should be further assessed.
Bursaphelenchus xylophilus causes pine wilt disease and is transmitted to host trees by cerambycid adults of the genus Monochamus. There are two primary transmission pathways: via vector feeding wounds to healthy trees and via the oviposition wounds to dying or recently dead trees. To determine the ratio of nematodes transmitted via the different pathways, M. alternatus female adults were reared on Pinus densiflora fresh twig sections and wood pieces with the bark made favourable for oviposition. Transmission curves of B. xylophilus to twig sections were similar in shape to the nematode departure curves for each vector, whereas the transmission curves to wood pieces were dissimilar to the departure curves because of different age classes at the peak between the curves. Consequently, there was no similarity in shape between two transmission curves to twig sections and wood pieces. Of B. xylophilus transmitted to twig sections and wood pieces after vectors constructed the first oviposition wound, 38.7% was transmitted to twig sections and 61.3% to wood pieces. Using the results of present and previous studies, GLM analysis indicated that the probability of B. xylophilus transmission to twig sections was 0.481 and that B. xylophilus had a 9.7 times higher likelihood of feeding-related transmission to oviposition-related transmission than non-pathogenic B. mucronatus. Thus, the reproductively mature vectors are considered to be related to the incidence of pine wilt disease and dispersal studies on mature vectors would help to predict the expansion rate of areas affected by the disease in the current year.
A population of the genus Devibursaphelenchus was collected from the inner part of the decaying Persian oak tree (Quercus brantii) from Lordegan city of Chaharmahal va Bakhtiari Province, Iran. The morphological and molecular characters confirmed the new species, namely D. lordeganensis sp. n. The new species is characterised by female body length (768-1026 μm), lip region separated from the rest of the body by a slight constriction, obscure lines on lateral fields, stylet length long, slender, wide-lumened, tripartite, composed of a conus with an aperture about half its length, a conophore about equal with the conus, and a shaft, taller than (conus + conophore) length, lacking basal knobs or swelling, excretory pore ca three metacorpal lengths posterior to the base of the metacorpus, post-uterine sac (PUS) (36-67 μm long; 1.3-3.7 times longer than vulval body diam.), absence or vestigial of rectum and anus, posterior end of the body conical with a rounded tip (in some specimens with a spherical protruded projection at tail tip), males 668 to 815 μm long, presence of two pairs of caudal papillae (P2 and P3), spicule length (15-17 μm) with long and wide bladed condylus, triangular rostrum with a blunt tip and small bursa flap ending at the tail tip. The molecular phylogeny based on 28S rDNA revealed that the new species stands close to D. alienae (LC629160) and D. lini (FJ768944, AM396570). The measurements, line illustrations, light microscopy photographs and phylogenetic analysis are given for the new species. In addition, a key to the species of Devibursaphelenchus is given.
A new species of the genus Ficophagus was recovered from the syconia of Ficus pisocarpa from Xishuangbanna, Yunnan province, China. It is described herein as Ficophagus pisocarpae n. sp. and is characterised by possessing the combined characters of a short PUS (6.4-9.3 μm or 0.3-0.4 VBD long), an excretory pore near the head, presence of crustaformeria, amoeboid sperm, three pairs of subventral papillae on the male tail (one pair just adcloacal (P2), one pair halfway between cloacal aperture and tail terminus (P3a), and one pair near tail tip (P4)), rounded male tail tip without mucron, absence of gubernaculum and rose-thorn-shaped spicule with conical rostrum. Ficophagus pisocarpae n. sp. was differentiated from other sequenced species by the partial small subunit (SSU) rRNA gene and D2-D3 expansion segments of the large subunit (LSU) rRNA gene. Phylogenetic analysis with the LSU D2-D3 expansion segment sequence suggested that F. pisocarpae n. sp. is clustered in the same highly supported monophyletic clade with F. annulatae, F. benjamina, F. curtipes and F. microcarpus. It differs morphologically from these species in lateral incisure number, EP position, spicule and uterus morphology and some morphometric characters.