A southern root-knot nematode (Meloidogyne incognita) first reported on cucumber in Manipur

Cucumber (Cucumis sativus) locally known as Thabi belongs to Cucurbitaceae family. It is an annual creeper/ climber widely grown in the statewith an area of 200 ha and production of 1580tonnes in 2020-21 (Anonymous, 2022). In Manipur, it is consumed as a salad or as boiled food while fresh fruit juice is used for local application on burns; fruit extract in relieving stomach problems and fruit paste forlocal application on the skin. The seeds are used as tonic, antipyretic, purgative and diuretic.
       
One of the major pests of vegetable crops, the root-knot nematode forms knots or galls in the infected roots, seriously impacting farmers’ produce. Berkeley (1855) discovered root-knot nematodes of the Meloidogyne spp. in cucumber plants produced in glasshouses in England. Barber (1901) made the first record of a plant parasitic nematode’s occurrence in Kerala (India), citing root-knot nematode, Meloidogyne spp. infesting tea. According to reports, 12.3% of the world’s major crops have annual yield losses as a result of damage by phyto-parasitic nematodes (Sasser and Freckman, 1987). Cucumber has been found to be vulnerable to most of the common species of root-knot nematodes, which can lower cucumber production in protected commercial cultivation by up to 60% (Ornat et al.,1997).
       
In the farmer’s field of Keirak village, in the Kakching block under Kakching district of Manipur, root-knot nematodes have been found to infest cucumbers (Fig 1). Under field conditions i.e., the above-ground, symptoms such as nutrient and water stress, yellowing of leaves, reduced plant growth, wilting and patchiness of crops was seen (Fig 2a).Heavy and compoundgalling of roots were observed in theinfested root showing the typical symptom of Meloidogyne spp. (Fig 2b).
 

 

       
The compoundroot system was first washed thoroughly without any damage and cut into small pieces of about 1cm in length followed by staining using the Acid Fuchsine method (McBeth et al., 1941). Meloidogyne spp. fully mature females were dissected into two parts after being removed from the stained roots. The additional trimming of the anterior half was done to retain the head end and it was mounted in a drop of simple plain lactophenol. The posterior half was similarly mounted and utilized to createperineal patterns (Taylor et al., 1955).By comparing characteristics found in the perineal area and the size and shape of the root-knot nematode with the description provided by Chitwood (1949) comparisons were made in order to identify the species.
       
Morphological studies of southern root-knot nematode, Meloidogyne spp. collected from cucumber crops from the Kakching district of Manipur. Female adults (n= 10): White body with a protruding neck, globular to pear-shaped (oval) form. In the neck and vulva-anus region, there are noticeable annulations. Lips set-off. The stylet is thin and has knobs that are clearly rounded. With a large, cylindrical procorpus and a rounded metacarpus, the esophagus is well-developed. Just behind the level of the style knobs is an excretory pore. Dorsally, the perineal pattern is wavy. The lateral lines are missing and the dorsal arch is high and squarish. There are vulva, anus and phasmid in the perineum (Fig 3). Consequently, the sample taken fromthe cucumber was found to be M.incognita.A similar observation was made by Chitwood (1949), who regarded the perineal pattern as the most notable and distinctive feature for identifying root-knot nematode species. According to Kaur and Attri (2013), the perineal pattern is the root-knot nematode’s most persistent characteristic.
 

The samples of infected plant roots from farmer’s field of Kakching district of Manipur have been found to be Southern root-knot nematode, Meloidogyne incognita infecting the cucumber plant. It is the first report recorded from Manipur, India.

The authors are highly obliged to the Project Coordinator, AICRP on Nematodes in Agriculture, ICAR-AICRP (Nematodes in Agriculture), PC Cell, IARI-New Delhi for providing financial support and also highly acknowledged the Director of Research, Central Agricultural University, Imphal, Manipur for providing necessary infrastructural facilities to carry out the research work.