First Report of Meloidogyne graminicola on Tomato (Solanum lycopersicum) in Hainan of China

Tomato (Solanum lycopersicum) is an important vegetable crop in Hainan province, Southern China. In this area, rice and tomato rotation is the most common way for tomato cultivation. During March of 2021, in a field of Yazhou District, Sanya City, Hainan Province, leaves of some tomato plants (cv. Jinsheng) turned yellow, although there were no obvious dwarf plants observed. The tomato plants with yellow leaves exhibiting obvious galls on the roots were collected. Several females and gelatinous egg masses of Meloidogyne spp. were found inside the cortex of the root galls after dissection. The perineal patterns of females (n=12) were dorsal-ventrally oval with low and round dorsal arches, lacking obvious lateral lines. Most of the striae were smooth and sometimes short and irregular striae were observed within them. Morphological measurements of females (n=20) included body length (L) = 569.2 ± 53.6 (457.6 - 662.7) µm, body width (BW) = 342.7 ± 69.8 (245.5 - 457.9) µm, stylet = 11.8 ± 0.7 (10.5 - 13.3) µm, dorsal pharyngeal gland orifice to stylet base (DGO) = 4.0 ± 0.2 (3.7 - 4.6) µm, vulval slit length = 24.1 ± 3.7 (16.7 - 30.7) µm, and vulval slit to anus distance = 16.0 ±1.9 (12.6 - 19.3) µm. The second-stage juveniles (J2s, n=20) had the following morphological characters: L = 440.6 ± 26.7 (395.7 - 488.3) µm, BW = 15.9 ± 1.0 (14.5 - 17.9) µm. stylet = 13.5 ± 0.8 (12.3 - 14.9) µm, tail length = 69.5 ± 3.7 (65.4 - 76.9) µm, hyaline tail terminus = 21.0 ± 2.1 (17.3 - 24.9) µm. These morphological characters matched the original description of Meloidogyne graminicola (Golden and Birchfield, 1968). Ten individual females were transferred to ten different tubes for DNA extraction. The species-specific primers Mg-F3 (5'-TTATCGCATCATTTTATTTG-3') and Mg-R2 (5'-CGCTTTGTTAGAAAATGACCCT-3') were used for the identification of M. graminicola (Htay et al. 2016). For the ten DNA samples, a 369 bp fragment was amplified by this pair of primers, confirming their identities as M. graminicola. The mitochondrial DNA (mtDNA) region between COII and the lRNA gene was amplified using primers C2F3 (5’-GGTCAATGTTCAGAAATTTGTGG-3’) and 1108 (5’-TACCTTTGACCAATCACGCT-3’) (Powers and Harris, 1993). A DNA fragment of 531 bp was obtained and the sequence (GenBank Accession No. MZ576221) was 99.8% identical to the sequences of M. graminicola (GenBank Accession Nos. MH033621, MK616527, and MG356945). Part of the rDNA spanning ITS1, 5.8S gene, and ITS2 was amplified with primers 18S (5’-TTGATTACGTCCCTGCCCTTT-3’) and 26S (5’-TTTCACTCGCCGTTACTAAGG-3’) (Vrain et al. 1992). The sequences from the ITS region were 790 bp (GenBank Accession No. MZ312595) and were all 100% identical to the known sequences of M. graminicola (GenBank Accession Nos. MF320126, HM623442, and KY020414). In glasshouse tests, six 30-day-old tomato plants (cv. Jinsheng) were individually transplanted in pots (V sand :V soil = 3:1) and inoculated with 1500 J2s hatched from the egg masses of collected M. graminicola samples per plant. Two non-inoculated tomato plants served as negative controls. After 50 days, inoculated plants had galled roots similar to those encountered in the field and there were J2s and eggs within the galls. The nematode reproduction factor (RF = final population/initial population) was 5.3. No symptoms were observed on control plants. These results confirmed the nematode’s pathogenicity on tomato. To our knowledge, this is the first time of a natural infection of tomato with M. graminicola in China.

Meloidogyne graminicola—A Threat to Rice Production: Review Update on Distribution, Biology, Identification, and Management

Rice (Oryza sativa L.) is one of the main cultivated crops worldwide and represents a staple food for more than half of the world population. Root-knot nematodes (RKNs), Meloidogyne spp., and particularly M. graminicola, are serious pests of rice, being, probably, the most economically important plant-parasitic nematode in this crop. M. graminicola is an obligate sedentary endoparasite adapted to flooded conditions. Until recently, M. graminicola was present mainly in irrigated rice fields in Asia, parts of the Americas, and South Africa. However, in July 2016, it was found in northern Italy in the Piedmont region and in May 2018 in the Lombardy region in the province of Pavia. Following the first detection in the EPPO region, this pest was included in the EPPO Alert List as its wide host range and ability to survive during long periods in environments with low oxygen content, represent a threat for rice production in the European Union. Considering the impact of this nematode on agriculture, a literature review focusing on M. graminicola distribution, biology, identification, and management was conducted.

Efficacy of Bio-agents in the Management of Root Knot Nematode (Meloidogyne graminicola) in Basmati Rice

Background: Rice root knot nematode (M. graminicola) is considered as a major threat in basmati rice. The main characteristic symptoms produced by M. graminicola are terminal hook shaped or spiral galls on the roots and other symptoms of damage include patches of stunted and yellowish plants. Methods: A field experiment was conducted in Kharif season of 2018 and 2019 at Sardar Vallabhbhai Patel University of Agriculture and Technology, Meerut (UP) to test the efficacy of bio-agents against the root knot nematode. In this experiment, three bio-agents (Bacillus pumilus, Bacillus subtilis and Pseudomonas florescence) and one chemical (carbofuran) were tested in randomized block design with three replications. Result: It was observed that tested bio-agents and chemical significantly reduced the galls per plant in comparison to the control. At 30 and 60 day after transplanting, minimum (12.7 and 10.0 galls/plant) and (20.9 and 18.8 galls/plant) were recorded with Bacillus subtilis @ 20g/ M2 (2 x 108 cfu/g) during 2018 and 2019, respectively. In case of control, 52.7 and 62.5 galls/plant were recorded at 60 days after transplanting during both years. All the tested bio-agents were found effective in reducing the nematode population, increase the growth parameters and yield of basmati rice.

Occurrence of Plant-Parasitic Nematodes of Turfgrass in Korea

Plant-parasitic nematodes are not only an important constraint on agricultural crop production, but also cause both direct and indirect damage to turfgrass, which is a ground cover plant. However, studies on plant-parasitic nematodes of turfgrass in Korea are scarce. A survey for plant-parasitic nematodes was carried out on 13 golf courses in Korea. The results yielded 28 species/taxa belonging to 16 genera and 12 families of plant-parasitic nematodes. Among the isolated species, <i>Helicotylenchus microlobus</i>, <i>Mesocriconema</i> <i>nebraskense</i>, <i>Tylenchorhynchus claytoni</i>, <i>Mesocriconema</i> sp., and <i>Meloidogyne graminicola</i> were the most prevalent species in all management zones. Twelve species were new records of plant-parasitic nematodes in Korea. Highest maximum densities were showed by <i>T. claytoni</i>, <i>Paratylenchus nanus</i>, <i>M. nebraskense</i>, <i>M. graminicola</i>, and <i>H. microlobus</i>. Diversity (<i>H’</i>), was significantly higher in fairways compared to tees and greens, though species evenness (<i>J’</i>) and dominance (<i>D</i>) showed no statistically significant differences. This information is crucial in nematode problem diagnosis, and the subsequent formulation of management strategies.

Non-coding RNAs in the interaction between rice and Meloidogyne graminicola

Background Root knot nematodes (RKN) are plant parasitic nematodes causing major yield losses of widely consumed food crops such as rice (Oryza sativa). Because non-coding RNAs, including small interfering RNAs (siRNA), microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), are key regulators of various plant processes, elucidating their regulation during this interaction may lead to new strategies to improve crop protection. In this study, we aimed to identify and characterize rice siRNAs, miRNAs and lncRNAs responsive to early infection with RKN Meloidogyne graminicola (Mg), based on sequencing of small RNA, degradome and total RNA libraries from rice gall tissues compared with uninfected root tissues. Results We found 425 lncRNAs, 3739 siRNAs and 16 miRNAs to be differentially expressed between both tissues, of which a subset was independently validated with RT-qPCR. Functional prediction of the lncRNAs indicates that a large part of their potential target genes code for serine/threonine protein kinases and transcription factors. Differentially expressed siRNAs have a predominant size of 24 nts, suggesting a role in DNA methylation. Differentially expressed miRNAs are generally downregulated and target transcription factors, which show reduced degradation according to the degradome data. Conclusions To our knowledge, this work is the first to focus on small and long non-coding RNAs in the interaction between rice and Mg, and provides an overview of rice non-coding RNAs with the potential to be used as a resource for the development of new crop protection strategies.

Management of rice root-knot nematode (Meloidogyne graminicola Golden and Birchfield)–An integrated approach

An experiment was conducted to know the efficacy of bio agents viz., Purpureocillium lilacinum, Trichoderma harzianum, Bacillus subtilis,Bacillus megaterium, Vermicompost and Consortium of bio-agents (Purpureocillium lilacinum + Trichoderma harzianum + Bacillus subtilis +Bacillusmegaterium +Vermicompost) and Carbofuran3G @ 0.3 i.e., alone for management of rice root-knot nematode Meloidogyne graminicola for one season at Chikadadakatte village of Honnali taluk, Davanagere district during Kharif- 2018. The results revealed that all the treatments were significantly superior over check with respect to growthparameters and nematode population. However, carbofuran 3G significantly reduced the nematode population (275.11 /200 cc soil)which was found to be the best treatment as it recorded highest plant height (114.06 cm), root length (23.13 cm), maximum grain yield (44.60 q/ha) with least RKI (1.20) followed byConsortium of bio-agents (Purpureocilliumlilacinum + Trichoderma harzianum + Bacillus subtilis +Bacillusmegaterium +Vermicompost).

Densidad de población de Meloidogyne graminicola en plantaciones comerciales de arroz y comportamiento de líneas avanzadas en la provincia de Los Ríos, Ecuador

En este estudio se determinaron las poblaciones de M. graminicola en suelo y raíces obtenidas en plantaciones comerciales de arroz en las zonas de Babahoyo y Quevedo del Ecuador. Para estudiar la tolerancia y/o resistencia al nematodo M. graminicola, se utilizaron un total de 50 líneas avanzadas F5 de arroz, de las cuales 35 son derivadas de cruces interespecíficos de Oryza sativa L. ssp. japonica x Oryza rufipogon G. (PUYÓN) y 15 líneas provenientes de cruces intraespecíficos de líneas de Oryza sativa L. ssp. japónica, incluyéndose también una variedad comercial de arroz, la INIAP 15, susceptible al ataque de M. graminicola, utilizada como control. La investigación se llevó a cabo en la Facultad de Ciencias Agropecuarias (FACIAG) de la Universidad Técnica de Babahoyo en Ecuador. Las evaluaciones de densidades poblacionales de M. graminicola conducidas en raíces y suelo, se realizaron en el Laboratorio de Fitopatología de la FACIAG. En base a los resultados obtenidos, se encontraron diferencias significativas en la respuesta entre las 50 líneas avanzadas F5 de arroz y la variedad comercial INIAP 15 a M. graminicola. En las condiciones evaluadas, las líneas 32 (PUYÓN/JP002 P11 – 10 P74), 5 (PUYÓN/JP002 P8 – 20 P13), 31 (PUYÓN/JP002 P11 – 10 P22) y 2 (PUYÓN/JP002 P8 – 20 P14), presentaron una baja densidad poblacional de M. graminicola en 10 g raíces. Por otro lado, las líneas 24 (PUYÓN/JP002-P8-28 P28), 28 (PUYÓN/JP002-P8-32 P33) y 30 (PUYÓN/JP002-P8-28 P28-11), presentaron una baja densidad poblacional de M. graminicola en 100 cm3 de suelo. En cuanto al índice de reproducción, el mayor número de veces que se multiplicó el nematodo fue 25 veces en la línea 7 (PUYÓN/JP002 P8 –28 P8-5) y el menor 2 veces en la línea 32 (PUYÓN/JP002 P11 – 10 P22).