Abstract
Summary Despite being the single largest cassava-producing country, yields in Nigeria remain consistently poor and among the lowest. Regionally, yields are also particularly low across Africa. Pests and pathogens, including plant-parasitic nematodes, play an important role in this current yield deficit. African countries are not only faced with the problem of food security but also that of nutritional deficiency, due to limited micronutrients in the diet. In this study, six biofortified cultivars were evaluated for their response to inoculation with approximately 30 000 root-knot nematode (Meloidogyne incognita) eggs in 30 l pots in Nigeria. All cassava cultivars proved highly susceptible to M. incognita infection after 6 months, with nematode reproduction factor ranging from 7.0 to 44.8. Galling was common on feeder roots and gall index scores were recorded between 4 to 5 (on a scale of 1-5 where 5 ⩽ 100 galls). Meloidogyne incognita infection significantly reduced plant height, stem girth, fresh plant mass, fresh storage root number and storage root weight. Percentage yield loss of between 41.8-88.4% was recorded in M. incognita-infected plants compared with non-infected controls. Although M. incognita reduced storage root weight, it did not necessarily affect the nutritional quality (total carotenoid) or dry weight percentage of the biofortified cassava cultivars. Total carotenoid and dry weight contents of the control cultivar were similar to some of the biofortified cultivars. The high susceptibility of the biofortified cassava cultivars to M. incognita infection indicates that substantial yield losses are likely being experienced by farmers, as this nematode pest is prevalent across sub-Saharan Africa and the tropics.
Highlights
Cassava (Manihot esculenta), a crop suited to conditions of low water and soil nutrient availability (Burelle, 2003), is among the most important staple foods across the humid tropics of Africa, Latin America and Asia
Biofortified cassava cultivars with significantly raised levels of provitamin A carotenoids and low hydrogen cyanide content have been developed by conventional plant breeding methods and released for use in Nigeria and the Democratic Republic of the Congo (HarvestPlus, 2011)
All biofortified cassava cultivars were susceptible to M. incognita infection, the level of susceptibility differed among the cultivars
Summary
Cassava (Manihot esculenta), a crop suited to conditions of low water and soil nutrient availability (Burelle, 2003), is among the most important staple foods across the humid tropics of Africa, Latin America and Asia. It plays a major role in efforts to alleviate the African food crisis because of its efficient production of food energy, year-round availability, tolerance to extreme stress conditions and suitability for small holder systems in Africa (Hahn, 1996). Pot studies have shown that root-knot nematode (Meloidogyne spp.) infection affected above-ground fresh weight, plant height, tuber weight and tuber number in susceptible cultivars (Coyne & Talwana, 2000; Akinsanya & Afolami, 2019). The current study was undertaken to assess the susceptibility and impact of the root-knot nematode, Meloidogyne incognita, on the production and nutritional content of biofortified cassava
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