Abstract:
Amaranthus species, with their adaptability to grow under various agro-ecologies and
soil types, have gained considerable attention in food security due to their high
nutritional content. However, various Amaranthus species are host to the root-knot
(Meloidogyne species) nematodes, with limited information on how the pest could
affect the nutritional composition of the crop. In other crops, infestation with
Meloidogyne species have deleterious effects on accumulation of certain essential
mineral nutrient elements. However, the influence of Meloidogyne species on essential
mineral nutrient elements had not been documented on Amaranthus. The objectives
of the study, therefore, were to determine the influence of infestation by Meloidogyne
species on growth and accumulation of selected malnutrition elements in four exotic
Amaranthus relative to the local cultivar under both greenhouse and field conditions.
In the greenhouse study, hardened-off seedlings were transplanted into 20-cm diameter plastic pots containing a steam-pasteurised growing mixture. The 5 × 2
factorial experiments were arranged in a randomised complete block design, with five
replications. The first and second factors were five Amaranthus cultivars and two
Meloidogyne species, namely, M. incognita and M. javanica. At 60 days after
inoculation, plant growth and nematode variables were assessed using standard
procedures. Roots of all five Amaranthus cultivars were heavily galled, with limited
cultivar × nematode interactions on plant variables. Additionally, the common factor
that influenced either plant or nutrient element variables was the cultivar type, whereas
those of nematodes were highly variable, particularly on nutrient elements. Three best
performing cultivars were further tested under field conditions under nematode
infested and untreated control plots. An exotic cv. ′Tanzania′ had higher dry shoot
mass, plant height and stem diameter, and accumulated higher Ca and K content than ′Candatus′ and ′Local 33′. Overall, the cultivar × nematode interaction reduced Na
content in leaf tissues of Amaranthus cultivars under field conditions.
