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Meloidogyne graminicola is one of the major plant-parasitic nematodes (PPNs) that affect rice agriculture. Rapid identification and quantification of M. graminicola in soil is crucial for early diagnosis so that measures can be taken to reduce the impact of PPN diseases and ensure food security. In this study, M. graminicola species-specific primers for conventional PCR, loop-mediated isothermal amplification (LAMP), and real-time PCR were designed based on the sequence-characterized amplified region. The primers were highly specific and sensitive, and only samples containing M. graminicola DNA showed positive results. The sensitivity of LAMP and real-time PCR (two second-stage juvenile [J2] M. graminicola in 100 g of soil) was higher than that of conventional PCR (200 J2s in 100 g of soil). A standard curve (correlation coefficient R2 = 0.970, P < 0.001) was generated by amplifying DNA extracted from 0.5 g of soil, and a significant correlation was observed between the number of M. graminicola determined by microscopic examination and that predicted from the standard curve (R2 = 0.477, P = 0.0160). In quantification analyses of M. graminicola isolated from 31 naturally infested soils, the sensitivity of LAMP and real-time PCR (22 M. graminicola in 100 g of soil) was higher than that of conventional PCR (211 M. graminicola in 100 g of soil). The conventional PCR, LAMP, and real-time PCR methods have the potential to provide a useful platform for rapid species identification according to the experimental conditions. The real-time PCR assay and standard curve can be used for quantification of M. graminicola. These newly developed assays will help to facilitate the control of these economically important PPNs.

Meloidogyne graminicola is an important pathogen of rice (Oryza sativa L.), and can cause yield losses of 11 to 80% (Mantelin et al. 2017). In June 2016, rice (cv. Fengyuanyou 2297) growing in direct seeding rice field in Hetang District, Zhuzhou City, Hunan Province, China, were observed with symptoms of leaf yellowing, stunting and many hook-shaped galls on the roots. Females, males and egg masses of Meloidogyne spp. were found within the galls after dissection. The morphological characteristics of females, males and second-stage juveniles (J2s) were observed and measured under an optical microscope at 100× and 400× magnification. The perineal patterns of females were dorsoventrally oval with low to moderately high and round dorsal arches and lacking obvious lateral lines; striae were usually smooth and fine, and broken by short and irregular striae in the dorsal part of the pattern; phasmids were small, distinct, and close together. Morphological measurements of females (n = 20) included body length (L...