Inheritance of high iron and zinc concentration in selected bean varieties

Abstract

Micronutrient malnutrition especially iron (Fe) and zinc (Zn) has disastrous consequences for the more vulnerable members of the human society, especially poor women and pre-school children in developing countries. The common bean (Phaseolus vulgaris L.), an important grain legume directly consumed by humans provides cheap and important quantities of protein and calories and is an excellent source of some minerals (Fe and Zn) and vitamins which qualify it as perfect food. Unfortunately, many of the adapted bean market class varieties are low in these nutrients. Therefore there is need for biofortification of these varieties with Fe and Zn through plant breeding and genetic engineering in order to contribute to improved health of bean consumers. The objective of this study was to determine the mode of inheritance of high Fe and Zn concentration in selected bean varieties. Six parents high and low in Fe and Zn were crossed following a full diallel crossing design. Populations were advanced from F1 to F2. F3 seed were analyzed for Fe and Zn concentration using X-ray fluorescence. The study showed that both additive and non-additive gene effects are important in determining the expression of high Zn and Fe concentration even though additive gene effects contributed more. Narrow sense heritability of Fe and Zn was high estimated at 71 % for Fe and 83 % for Zn. Significant maternal and reciprocal effects suggest also that cytoplasmic inheritance is involved in Zn and Fe concentration. Strong positive correlation between Fe and Zn concentrations (r = 0.75) was observed suggesting that these micronutrients are not independently inherited. The positive relationship between Fe and Zn plus the negative relationship observed between Zn and seed size (r = 56) suggest that Zn and Fe accumulation is controlled multigenically or oligogenically with some genes affecting the concentration of both minerals. The variability in seed mineral concentration among crosses was larger for Fe (47–77 ppm) than for Zn (28–38 ppm).