Intra-specific morphological and morphometric variability of Radopholus similis (Cobb, 1893) Thorne, 1949

Abstract

Abstract:All the root inhabiting migratory endoparasitic nematode populations of Radopholus procured from banana crop of Vellayani, Thiruvananthapuram, Kerala were identified as Radopholus similis. Heat killed females were straight to slightly ventrally curved posteriorly. Female's head was low, rounded, continuous or slightly setoff with the body contour.Females were 500-660 µm long and were comparatively longer than males. Males had button shaped head set off by a constriction; female with three to five lip annuli, four crenate and areolated lateral incisures, stylet 14-18 µm long with rounded knobs, vulva postequatorial (58%), sometimes with slight protuberant lips, ovary paired and equally developed, oesophageal gland overlapped the intestine dorsally, tail elongate-conoid with narrowly rounded terminus. The stylet length (µm), width of stylet knob (µm), distance of excretory pore from anterior end (µm), distance from head to basal bulb (µm), lateral field structure, shape of stylet knob, head region, position of phasmid, tail shape with its terminus, morphometric values like m%, o% and v% and a, c and c´ ratios of females were stable (CV<12%) features. There is an existence of intra-specific variability in the morphological and morphometric features of R. similis. The main morphological diversity was observed with P% of male and female, b ratio of female and stylet length, distance of DEGO from stylet base, o% and T% of male. All the root inhabiting migratory endoparasitic nematode populations of Radopholus Thorne, 1949 procured from banana of Vellayani, Thiruvananthapuram, Kerala were identified as Radopholus similis (Cobb, 1893) Thorne, 1949. A high degree of intra-specific morphometric variability was observed with regard to the total body length (µm), body width (µm), stylet length (µm), distance of dosrsal oesophageal gland orifice (DEGO) from stylet base (µm), number of lip annuli, lip height (µm), distance from head to basal bulb (µm), distance of anus from anterior end (µm), tail length (µm), anal body width (µm), distance of phasmid from tail terminus (µm), number of lateral lines, width of lateral field (µm), b ratio and P % among females of R. similis. Morphometric features like m%, o% and v% of females of R. similis showed least variability. These can be considered as the stable morphometric characters for discrimination of females of R. similis. Ratios like 'a' and 'c' of females of R. similis were found moderately variable. The morphometric feature and of male i.e. distance from head to basal bulb (µm) was found least variable; while number of lip annuli and spicule length (µm) were moderately variable.

Molecular approach to confirm traditional identification of Radopholus similis sampled in Tanzania

“…Identification and characterization of R. similis showed that this nematode species was present in banana crops in all agro-ecological zones included in this study, making it a potential threat to banana production in Tanzania. Morphological and morphometric characterization of R. similis generally concurred with descriptions and measurements reported in other studies ( Ryss and Wouts, 1992 ; Elbadri et al, 1999 ; Murukesan et al, 2005 ; Roy et al., 2018 ). Most R. similis specimens from Zanzibar had greater total body length than those from the mainland.…”

“…However, we found that male and female stylet lengths fell outside of standard diagnostic values ( Ryss and Wouts, 1992 ; Elbadri et al, 1999 ), possibly due to variations in environmental conditions that drive morphological adaptation. We also found that males had slender bodies compared to females and degenerated stylets in all zones, reflecting the lower level of damage that males inflict as reported by Ryss and Wouts (1992) and Roy et al (2018) .…”

“…Differences in morphological parameters among the regions were tested using analysis of variance in GENSTAT (14th edition, VSN International Ltd, Hemel Hempstead, UK) to compare the means using the least significance difference test with a statistical threshold of p < 0.005 ( Roy et al, 2018 ).…”

The abundance of phytonematodes associated with ginger plants in the District of Bogor, Cianjur, and Sukabumi, West Java

“…The nematode Radopholus similis recovered from this study showed morphological similarities as reported in India [15]. The body position of the female R. similis is straight, and the tail is slightly curved when during the fixation.…”

Caracterización morfométrica y molecular de poblaciones de Radopholus similis [(Cobb) Thorne (Rhabditida: Pratylenchidae)] en Colombia

“…Según Ryss (2003), en nematodos pertenecientes a la familia Pratylenchidae, el valor del carácter alométrico b se incrementa durante el crecimiento postembrionario, debido a la elongación del cuerpo. En este sentido, Roy et al (2018) encontraron variabilidad en el carácter alométrico b en diferentes poblaciones de R. similis de la India, lo cual contrasta con los altos valores en estos caracteres para la población de Carepa, posiblemente debido a las condiciones específicas de ambiente y hospedante en esta región; los cuales pueden influir en el fenotipo resultante para esta población.…”