Prevalence of Plant Nematodes Associated with Maize in Balochistan, Pakistan

Samples were collected from eight maize growing areas namely Anjira, Kalat, Khazeena, Khuzdar, Mangochar, Rodeni, Surab and Zehri of Balochistan, Pakistan in the middle of the crop growing period which was first week of November, 2016. Different nematicides are commonly applied at planting but in these eight localities no nematicide was used prior to sowing. Soil in

the region contained 44-52% sand. Six plants were arbitrarily selected in each field. Rhizosphere soil collected from six plants was pooled together to obtain 100 ml sample (Table 1). For root-knot nematodes 5g of root from each sample was macerated in water in a kitchen blender (De Wade et al., 1998). The females of root-knot nematodes were cleaned in lactic acid (45%) and mounted in pure anhydrous glycerol (Taylor and Netscher, 1974). The rhizosphere soil samples were processed according to Cobb’s modified decanting and sieving method (S’Jacob and Van Bezooyen, 1984). Nematodes were killed with hot formalin-propionic acid (FP 4:1), processed using Seinhorti’s (1959) rapid glycerol-ethanol method, and mounted in pure glycerin. Most nematodes were identified up to species level.

For statistical analysis the differences in the density of nematode species among localities were analyzed using one-way ANOVA, least significant test (L.S.D.) at p-level of 0.05 and Duncan’s multiple range test (DMART) (Zar, 2008).

The nematodes recorded were Aglenchus (Andrάssy (Mcyl) sp., Aphelenchus avenae Bastian, Longidorus Micoletzky sp., Hoplolaimus pararobustus (Schuurmans Stekhoven and Teunissen) Sher; Helicotylenchus dihystera (Cobb) Sher; Meloidogyne incognita (Kofoid and White) Golden; Pratylenchus zeae Graham; P. penetrans (Cobb) Filipjev & Schuuvmans Stekhoven; P. thornei Sher and Allen; P. goodeyi Sher and Allen; Scutellonema brachyurum (Steiner) Andrάssy; Bitylenchus goffarti (Sturhan) and T. mashhoodi Siddiqi and Basir. For the plant nematode Bitylenchus goffarti there was a significant difference in density (F = 17.53; p < 0.001) among localities. Meloidogyne incognita larvae also showed significant difference among the localities (F = 10.16; p < 0.001) with the highest density in Mangochar. Tylenchorhynchus mashhodi was recorded only from Kalat. Pratylenchus thornei had a significant difference in density (F = 11.302; p < 0.001). Longidorus sp. was recorded in one locality Anjira with a mean value of 2.4. Scutellonema brachyurum was only recorded in Kalat with mean value of 7.5. Similarly, Aphelenchus avenae was also recorded only in Khuzdar with an average density of 11 and Hoplolaimus pararobustus was also present in one locality Khuzdar with an average density of 57.5. For Helicotylenchus dihystera the difference in mean density for Khazeena and Zehri was non-significant. Pratylenchus goodeyi was prevalent only in one locality with a mean density of 6. Pratylenchus zeae occurred in most localities namely Khazeena Mangochar, Rodeni, Surab and Zehri with a maximum density in locality Rodeni (density = 171.4) and minimum in locality Mangochar (density = 56.3). The overall difference among mean densities was significant (p < 0.001). Aglenchus sp. was found in one locality Zehri with an average mean density of 13 and finally Pratylenchus penetrans was recovered in three localities namely Mangochar, Rodeni and Zehri with a mean density of 17.5 and the difference between localities was significant (F = 4.05; p < 0.05). Norton (1983) suggested that Hoplolaimus sp. and Pratylenchus sp. presence in the rhizosphere soil of maize can be extremely low while several thousand of nematodes may be present in a single gram of root tissue thus for proper results maize root tissue by proper macerating can give accurate results. Since Meloidogyne sp., Pratylenchus spp. and Longidorus sp. were encountered in the present survey. Their feeding and migrating destructively through root tissue or acting as vector of virus can be extremely harmful to maize crop. As suggested by Kayani et al. (2018) early diagnosis of root-knot nematode can abate heavy losses.

The culture methods for management of nematode are very successful besides being environment friendly. As far as the chemicals are concerned they require applications of large amounts of chemicals using specialized equipment. Moreover, besides being costly, chemicals can be extremely harmful to humans and other non-target organisms. The most successful approach to plant nematode control could be only in conjunction with other management tactics including cultural practices (non-host crop, rotations or growing cover crops that could be nematode antagonists and if necessary chemical treatment of soil provide efficient control. Cover crops such as marigold (Tagetes erecta) and rattlepods (Crotalaria) can be employed.

The authors declare no conflict of interest.