Abstract
Pests including nematodes have been reported as a limiting factor to the production of roselle worldwide. A survey of rosellefarmsinsix Northern Sates of Nigeria was conductedin 2013 to identify the diverse nematode species associated with the soils and roots of the plant and determine their population densities on farmers’ fields. Eightsoil and ten plant samples were randomly collected from each of twenty farms from which nematodes were extracted and identified. Four genera of plantparasitic nematodes ( Meloidogyne spp., Helicotylenchus spp., Rotylenchulus spp.and Tylenchus spp.) were found in association with roots and rhizosphere of roselle plants. Meloidogyne were most populous (62.29%) on the roots while Tylenchuswas least (1.68%). Helicotylenchus spp appeared in highest density (50.05%) in plant rhizosphere, but not identified from the roots. The highest percentage of nematode population (22.7 %) wasfrom Katsina, followed by Sokoto (21.6%), Jigawa (17.4%), Zamfara (16.5%), Kano (15.1%) and Kaduna states (6.7%).The generally low nematode density observed might be due to low precipitation and high soil temperature of the six states. Occurrence of varied species of nematodes demands effective control measures for improved roselle productivity. Kano, Zamfara and Jigawawith low nematode population densities can be considered for further research towards the establishment of pest-free areas or area of low pest prevalence for roselle nematodes in Nigeria, useful in the agricultural export trade. Further studies are required on the determination of density economic threshold and the definitive roles of nematodes in causing low productivity of roselle. Keywords: Export value, Hibiscus sabdariffa , nematodes, population densities, pest-free area
Highlights
Roselle (Hibiscus sabdariffaL.) called rosella, sorrel or java jute is a fibre crop of the family Malvaceae
Many farmers in the study areas shifted from cultivating roselle to other crops due to poor marketing and while only one roselle farm per Local Government Areas (LGAs) was found in some locations, two or three farms were observed in others
This study showed that while the highest population of Helicotylenchus spp. was observed in the soils across the six states, Meloidogyne spp were most abundant in the roots of roselle plants
Summary
Roselle (Hibiscus sabdariffaL.) called rosella, sorrel or java jute is a fibre crop of the family Malvaceae. Its extensive cultivation in Indonesia began in the 1920s under a governmentsubsidized program established to obtain fibre for sugar-sack manufacture. It is commercially propagated in different parts of the world including USA, United Kingdom and India while Benin, Sudan, Cote D’Ivoire, Ghana, Niger, Burkina Faso and Nigeria were reported as major areas of roselle cultivation in Africa (Oyewole and Mera, 2010; Babatunde and Mofoke, 2006)India, Java, and the Philippines are the world major producers (EBI, 2017; Orwa et al, 2009). The two main varieties of sHibiscus sabdariffa are H. sabdariffavar. The variety H. sabdariffa has red or pale yellow inflated edible calyces but a poor quality fibre
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