Diversity of common bean (Phaseolus vulgaris L.) genotypes in iron and zinc contents under screenhouse conditions

Deficiencies in iron and zinc have health consequences for humans, such as anaemia, poor growth and development in children and low productivity in adults. To guarantee sufficient supply of iron and zinc through diet mainly consisting of staple foods, such as common bean (Phaseolus vulgaris L.), specific interventions in plant breeding are needed. However, seed mineral content has not been a selection criterion for plant breeding, although genetic variation for this trait is present in available germplasm collections. The aim of this study was to evaluate variability of iron and zinc concentrations among common bean genotypes grown in four major bean growing areas in Tanzania for breeding work. Ninety genotypes collected were evaluated under screen house at Sokoine University of Agriculture. A completely randomized design with three replications was used. Seeds and leaves were collected, dried, ground and the powder was used for iron and zinc determination using atomic absorption spectrophotometer. Variation in iron and zinc contents was observed among genotypes both in seeds and leaves and best genotypes identified. Results have shown a positive and significant correlation(r=o.416;P<0.001) between iron and zinc, suggesting that genetic factors for increasing iron and zinc are co-segregating with genetic factors for increasing zinc. Leaves of the studied varieties have moderate level of zinc (28.0 ppm) and high level of iron (310.0 ppm) forming good source of micronutrients in combating micronutrient malnutrition. Genotypes with high level of iron and zinc should be used as a gene source in future breeding work.