Growth, yield and disease responses of 12 cassava genotypes evaluated for two cropping seasons in a derived savannah zone of southeastern Nigeria

Ten new cassava genotypes selected for high yield and tolerance to some biotic stresses were evaluated alongside the local best, Otupam and ‘TMS 30572\' (a widely cultivated hybrid genotype, as an improved check) for two cropping seasons with a view to obtaining suitable genotype(s) that could be recommended for release to farmers. The results revealed that only TMS-96/0304, TMS-96/1672 and NR-930255 had above 90% sprout survival at 12 months after planting. Severity of cassava mosaic disease (CMD), cassava anthracnose disease (CAD) and cassava bacterial blight (CBB) varied among genotypes, plant age, and the cropping year. Symptom expressions of CMD and CBB were generally higher on the local best, Otupam and NR-930255. The severity of cassava green mite was moderate and statistically similar on all the genotypes while severity of cassava mealybug was mild. Hybrids NR930255, TMS96/1672 and TMS96/0304 produced the highest number of tubers. These genotypes also significantly (P< 0.05) produced the highest harvested tuber yield per hectare: NR 930255 (31.0 t/ha), TMS 96/1672 (28.0 t/ha) and TMS 96/0304 (29.4 t/ha). The three genotypes had the least percent yield difference between the potential and the actual yield. Mean rank-sum for all traits measured suggested that the most adaptable genotypes to Nsukka agro-ecology after two years of evaluation were NR-930255, TMS 96/0304 and TMS96/1672, but the poor disease ratings for NR-930255 and TMS 96/0304 precluded their recommendation for release while TMS 96/1672 could be recommended for release to farmers

Breeding for enhanced ß-Carotene content in cassava: constraints and accomplishments

This review presents an overview of the importance, constraints, and prospects on different aspects of cassava (Manihot esculenta crantz) breeding for enhanced micronutrient level, including carotenoids (precursors for provitamin-A) and especially beta-carotene. Early cassava-breeding efforts concentrated on crop yield, dry matter, and disease resistance, which are farmer-preferred traits. However, unacceptably high levels of preventable human diseases caused by malnutrition prompted breeders and nutritionists to screen wild relatives and unimproved germplasms (landraces) to increase micronutrient density in staple crops. The ultimate objective is to reduce diseases caused by micronutrient deficiencies. Nigeria, with 140 million people and the largest producer and consumer of cassava in the world, is characterized by rampant malnutrition and high incidence of nutrient deficiency-related diseases. The tuberous root of cassava is low in micronutrients. It is also well known that vitamin A deficiency is primarily caused by dietary inadequacy that results in progressive eye damage and eventually leads to blindness, especially in children. In addition, affected children suffer from a weakened immune system. Present interventions to eliminate this deficiency rely on supplementation and food fortification programs, do not reach all those affected and do not get to the root of the problem, which is an inadequate diet. The development of high micronutrient-content cassava varieties (especially, higher ?-carotene and other carotenoids) will contribute to a more sustainable solution of the problem of vitamin A deficiency. A current thrust of research (HarvestPlus initiative) is to determine the genetic potential for increasing the concentrations of bioavailable Fe, Zn, and provitamin A carotenoids in the edible portions of several staple food crops including cassava, rice, wheat, maize, and beans. Currently, the International Institute of Tropical Agriculture (IITA), International Center for Tropical Agriculture (CIAT), and National Root Crops Research Institute (NRCRI), Umudike, are working in collaboration to develop an elite cassava gene pool and to develop varieties that will be released to farmers soon in hope of addressing part of micronutrient malnutrition