Twenty-one yellow-fleshed cassava genotypes were evaluated over two years in five major cassava growing agroecological zones in Nigeria. The trials were established in a randomized complete block design with four replications to assess genotype performance and Genotype × Environment interaction for cassava mosaic disease (CMD), fresh and dry root yield (FYLD; DYLD), root dry matter content (DMC), and total carotene concentration (TCC). Combined analysis of variance showed significant differences ( ) among genotypes (G), environment (E), and Genotype × Environment interaction (GE) for all the traits tested. For reaction to CMD, the best genotypes showing stable resistance were TMS 07/0539 and TMS 07/0628. For root yield, the best genotypes were TMS 01/1368 and TMS 07/0553. Genotype TMS 07/0593 was the best for DMC and TCC across the 10 environments. Variation among genotypes accounted for most of the Total Sum of Squares for CMD (72.1%) and TCC (34.4%). Environmental variation accounted for most of the Total Sum of Squares for FYLD (42.8%), DYLD (39.6%), and DMC (29.2%). This study revealed that TMS 07/0593 has the highest and most stable TCC, DMC with the lowest CMD severity score and appeared to be the best genotype. 1. Introduction Vitamin A deficiency (VAD) is a global problem of public health significance in under-privileged communities of the world [1]. Xerophthalmia is the most readily recognized and the most widely employed criterion for discussing whether VAD poses a significant public health problem in any particular community [2]. Vitamin A deficiency in the early stage leads to night blindness and Xerophthalmia, which may ultimately progress to blindness [3]. A nationwide food consumption and nutrition survey conducted in Nigeria revealed that 29.5% of children under 5 years of age were vitamin A deficient (serum retinol <0.70？ mol/L) [4]. Cassava (Manihot esculenta Crantz) is an important food security crop and a major source of calories for about two of every five Africans [5]. Although the starchy root is the primary product, fresh leaves are also used for animal and/or human consumption [6]. In 2008, Nigeria was the leading cassava producing country in sub-Saharan Africa, producing 44.6 million tons on 3.8 million ha [7]. In Nigeria, more than 70% of cassava production is processed at the village level into gari, the principal source of calories for 70–80 million Nigerians. Cassava varieties often demonstrate specific adaptation due to their high sensitivity to the genotype-by-environment interaction (G E) that occurs in both short-term
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