Review Paper On Breeding Common Bean Phaseolus Vulgaris L. Genotypes For Acidic Soil Tolerance

Common bean Phaseolus vulgaris L. is a food legume grown on more than four million hectares annually in Africa. It provides dietary protein for over 100 million people in rural and poor urban communities with an annual per capita bean consumption of 50 to 60 kg in Eastern Africa being the highest in the world. Common bean provides proteins essential amino acids minerals such as Fe Cu Zn P K Mg and Ca starch and dietary fibre which are less or absent indiets of of subsistence farmers in Africa and South America often contain high carbohydrates through cassava maize rice wheat. Eventhough the crop has this much contripution in the daily livelihood of the society its production is affected by some biotic and abiotic factors. Soil acidity affects the bean production through different mechanisms including Aluminium and Mangans toxicity and inhibition of essential nutrientP KN avaliability to the crop. Aluminuim toxicity affect the growth and development of the crop by restricting root growth and enlongation. Even though Aluminum toxicity reduces both root and shoots growth the most easily recognized symptom of A1 toxicity is the inhibition of root growth and this has become a widely accepted measure of Al stress in plants. Common bean can tolarate Al toxicity through different mechanisms. Aluminum tolerance can be divided into mechanisms that facilitate Al exclusion from the root apex external tolerance mechanisms and mechanisms that confer the ability to tolerate Al in the plant symplasm internal tolerance mechanisms