Taxonomy, Morphological and Molecular Identification of the Potato Cyst Nematodes, Globodera pallida and G. rostochiensis

Anatomical Alterations Caused by Meloidogyne incognita in the Rhizospheric Region of Curcuma longa in Baruasagar Town of Jhansi (U.P.) India

Root-knot nematodes Meloidogyne incognita are sedentary endoparasites with a broad host range which includes economically important medicinal plant species including Turmeric. Turmeric (Curcuma longa) is an important medicinal and aromatic plant (MAPs) grown at Baruasagar town in Jhansi district where root-knot nematodes are a major threat in production fields. The invasion of M. incognita causes serious morphological abnormalities like stunted growth and yellowness of leaves above the ground and the formation of galls at the rhizospheric root, below the ground. The infected root samples of C. longa were collected from three different agro-ecosystem zones of Baruasagar town of Jhansi and processed for optical microscopic investigation. For ascertaining the histopathological modifications, the galled roots were collected and the egg masses were picked from them for culture. The giant cells observed with thicker irregular cell walls and possessed dense cytoplasmic contents with multiple nuclei.

Molecular insights into Solanum sisymbriifolium's resistance against Globodera pallida via RNA-seq

BACKGROUND

The presence of potato cyst nematodes (PCN) causes a significant risk to potato crops globally, leading to reduced yields and economic losses. While the plant Solanum sisymbriifolium is known for its resistance to PCN and can be used as a trap crop, the molecular mechanisms behind this resistance remain poorly understood. In this study, genes differentially expressed were identified in control and infected plants during the early stages of the S. sisymbriifolium - G. pallida interaction.

RESULTS

Gene expression profiles were characterized for two S. sisymbriifolium cultivars, Melody and Sis6001, uninfected and infected by G. pallida. The comparative transcriptome analysis revealed a total of 4,087 and 2,043 differentially expressed genes (DEGs) in response to nematode infection in the cultivars Melody and Sis6001, respectively. Gene ontology (GO) enrichment analysis provided insights into the response of the plant to nematode infection, indicating an activation of the plant metabolism, oxidative stress leading to defence mechanism activation, and modification of the plant cell wall. Genes associated with the jasmonic and salicylic acid pathways were also found to be differentially expressed, suggesting their involvement in the plant's defence response. In addition, the analysis of NBS-LRR domain-containing transcripts that play an important role in hypersensitive response and programmed cell death led to the identification of ten transcripts that had no annotations from the databases, with emphasis on TRINITY_DN52667_C1_G1, found to be upregulated in both cultivars.

CONCLUSIONS

These findings represent an important step towards understanding the molecular basis underlying plant resistance to nematodes and facilitating the development of more effective control strategies against PCN.

Morphological and Molecular Characterization, Including Parasitic and Pathogenic Studies of a New Spherical Cyst Nematode Species, Globodera vulgaris n. sp. (Nematoda: Heteroderidae), Associated with Potatoes in China

In this study, a new spherical cyst nematode belonging to the genus Globodera, herein described as Globodera vulgaris n. sp., was extracted from the roots and rhizosphere soil of potato and circumjacent weeds belonging to different families in three provinces in southwest China. The new species was characterized by 8 to 24 ridges between the anus and fenestra and an average Granek's ratio of 2.8 to 3.8 in cysts, a head with three to four annules, a dorsal knob anteriorly projected, ventral knobs round or anteriorly projected in second stage juveniles, a head with three to five annules, a short spicule with an average length of less than 30.0 μm, and a developed velum in males. Pathogenicity tests showed that G. vulgaris n. sp. infected potato but did not damage or affect the potato yield compared with the control, and it parasitized tomato with a low reproduction rate (RF < 1) while it did not parasitize tobacco (RF = 0). The new species was closely related to G. rostochiensis, based on molecular diagnostic marker sequences and constructed phylogenetic analysis, based on internal transcribed spacers of ribosomal DNA, large-subunit rDNA, and small-subunit rDNA. However, the new species exhibited differences from G. rostochiensis in terms of morphological characteristics, a wide host preference, lack of damage to hosts, and an egg-hatching rate induced by hatching factors.

Top Ten Most Important U.S.-Regulated and Emerging Plant-Parasitic Nematodes

Plant-parasitic nematodes (PPNs) are important pests that cause an estimated ten billion dollars of crop loss each year in the United States and over 100 billion dollars globally. The Animal and Plant Health Inspection Service (APHIS) within the U.S. Department of Agriculture maintains and updates the U.S. Regulated Plant Pest list. Currently, the number of PPNs regulated by APHIS includes more than 60 different species. This review focuses on the top ten most economically important regulated and emerging plant-parasitic nematodes and summarizes the diagnostics of morphological and some molecular features for distinguishing them. These ten major previously described nematode species are associated with various economically important crops from around the world. This review also includes their current distribution in the U.S. and a brief historical background and updated systematic position of these species. The species included in this review include three PPNs considered by the U.S. Department of Agriculture as invasive invertebrates Globodera pallida, Globodera rostochiensis, and Heterodera glycines; four regulated PPNs, namely Bursaphelenchus xylophilus, Meloidogyne fallax, Ditylenchus dipsaci, and Pratylenchus fallax; and the three emerging PPNs Meloidogyne chitwoodi, Meloidogyne enterolobii, and Litylenchus crenatae mccannii.