Zinc biofortification on root yield and quality performance of cassava varieties grown in Umudike, southeast Nigeria

Abstract

A field study was conducted at Michael Okpara University of Agriculture, Umudike (latitude 05° 28´ 51´´ N, longitude 07° 32´ 25´´ E, 120 m.a.s.l), Nigeria in 2021/2022 cropping seasons to evaluate the response of cassava (Manihot esculenta Crantz) varieties to zinc biofortification. The treatments comprised of all combinations of the three cassava varieties (TME 419, TMS 01/1371, TMS 98/0581) and three zinc rates (0, 5 10 kg/ha) in the form of zinc sulphate (ZnSO4•7H2O) which were fitted into a randomized complete block design with three replications. Results indicated that the varieties were similar values for all the varieties except starch percentage, β-carotene content, root zinc content 
and zinc recovery efficiency (REzn). The application of zinc induced a positive response of root yield across the cassava varieties. Highest fresh root yield, starch percentage, β-carotene content, root zinc content and zinc recovery efficiency (REzn) were obtained at the application of zinc rate of 10 kg and 5 Kg ZnSO4.7H2O/ha. However, there was non significant interaction between variety and Zn application. Root length and weight of marketable roots/plant exhibited positive and significant correlation with root yield of cassava while the regression analysis indicated that the level of 
contribution of starch yield and weight of marketable roots/plant to fresh root yield was at 28.10 and 3.07 per cent, respectively indicating that yield of the cassava varieties increased positively due to the effect of these variables. The cassava variety (TMS 01/1371) that received 10 kg ZnSO4.7H2Oꞏha-1 gave the highest fresh root yield closely followed by the interaction between these varieties (TMS 98/0581 and TME 419) and 10 kg ZnSO4.7H2Oꞏha-1. The least root yield was recorded under TMS 98/0581 × 0 kg ZnSO4.7H2Oꞏha-1. The highest zinc uptake in roots, root zinc content and zinc recovery efficiency were recorded under the interaction treatment of cassava variety (TMS 01/1371 × 5 kg ZnSO4.7H2Oꞏha-1). Therefore, for increased root yield, TMS 01/1371 × 10 kg ZnSO4.7H2Oꞏha-1 can be adjudged to be a viable option while for improved zinc biofortification in cassava roots, TMS 01/1371 × 5 kg ZnSO4.7H2Oꞏha-1 may be considered for adoption by farmers in the agro-region.