Aims: To identify the nematodes profile (species) and determine their population density ravaging elite plantain cultivars in southern Nigeria.
Study Design: The study was a survey of 318 plantain accessions planted in-situ and maintained in farmers’ fields within the study area. Cluster analysis was performed to generate the clusters groups or elite cultivars from which soil and root corm samples were taken from ratoon crop of each cultivar location for analysis.
Place and Duration of Study: The laboratory experiments were conducted in the Department of Genetics and Biotechnology, University of Calabar, Cross River State in 2014 and 2015.
Methodology: The tray extraction (Modified Baermann) method was adopted for soil nematodes while the root maceration followed by incubation method was adopted for the root corm nematode extraction. The Genstat software was used for the analyses of data generated from the study.
Results: Results of nematode densities (population) per 10 g of root corm, ravaging elite plantain cultivars showed significant (p<0.05) differences in the population of nematodes infesting plantain crop in the root corm for the two cropping cycles of 2014 and 2015 investigated. The burrrowing nematode populations were highest in Bakpri (dwarf mutant) plantain cultivars (461/10g corm tissue in 2014 and 493/10g corm tissue in 2015 respectlvely) compared to all other cultivars. Ekumkwam cultivar seem to have the least population of burrowing nematodes of 9/10g corm tissue in 2014 and 13/10g corm tissue in 2015 respectively.
Results of nematode densities per 100g of soil, ravaging elite plantain cultivars reveal some significant (p<0.05) differences in the population of nematodes infesting plantain crop for the two cropping cycles of 2014 and 2015 investigated. Nematodes population in root soil were highest in the Bakpri (dwarf mutant) plantain cultivars (12,344/100 cm³ soil in 2014 and 10,416/100 cm³ soil in 2015 respectively) compared to all other cultivars. Ikpobata (cooking banana) cultivar seem to have the least population of nematodes (93/100 cm³ soil in 2014 and 78/100 cm³ soil in 2015 respectlvely).
The results also shows that the profiles of nematodes found to be ravaging elite plantain cultivars in the study area were the burrowing nematodes Radophilus similis, the ectoparasitic and spiral nematodes, Helicotylenchus multicintus and the soil migratory nematodes, Practylenchus goodeyi. Of the total nematode populations extracted from both rhizosphere or root soil from the fourteen (14) locations, they varied (P<0.05) significantly in density and concentration. The results showed that the ectoparasitic and spiral nematodes, Helicotylenchus multicintus had the highest profile density of 68.45% of all nematodes extracted from the root soil in all the elite cultivars sampled. The soil migratory and sedentary nematodes, Practylenchus goodeyi had a profile population of 27.12% while the burrowing nematodes, Radophilus similis, showed the least profile density in soil consisting of 3.51% while the unidentified organisms in the extracts were 0.02% in their profile density.
Results of nematodes profile density isolated from 10g root corm of all elite plantain cultivars revealed that, the burrowing nematodes, Radophilus similis had the highest profile density in the root corm constituting about to 76.11% of the total nematodes extracted from the root corm while the migratory nematodes Practylenchus goodeyi showed a nematodes profile density of 22.84%. Unidentified organisms were 0.54% while the ectoparasitic nematodes, Helicotylenchus multicintus constituted the least 0.51% profile density.
Conclusion: This study has shown that the low yield experienced by farmers in plantain fields in this agro-ecosystem can highly be attributed to high nematodes densities and significant profile densities which have not allowed for the full realization of the productive potentials of elite plantain cultivars in the area despite their nutritional and economic benefits. In view of the perceived potential of Plantain Parasitic Nematodes to destroy and reduce the yield of plantains, conscious efforts must be made to develop a sustainable management option for these pests. The use of soil mulch, local soil additives and plant extract as alternatives to synthetic Nematicide is strongly advocated in the region in view of the effect of pesticides on the environment and food chain.