Productivity and malnutrition elements in local and exotic Amaranthus cultivars

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.