Genetic Variation for Nitrogen Fixation, Micronutrient Density and Influence of Plant Growth Promoting Rhizobacteria and Fertilizers on common Bean (IRO scholarship)

50000403v1625
Promoter: Jos Vanderleyden


Description: Evidence is growing that our global food systems are failing to deliver adequate quantities of healthy, nutritionally balanced food especially to under-privileged people globally. The consequences are poor human health, declining productivity and poor livelihoods. This has contributed to stagnating national development efforts in many developing nations. Protein and micronutrient deficiencies in local diets are widespread problems in Africa. The problems are now recognized as one of the most serious health challenges facing vast sectors of Africa’s population; particularly resource-poor women and children. The most deficient nutrients include iron and zinc. Although food fortification and supplementation are being implemented as strategies to reduce micronutrient malnutrition, the two strategies are limited in coverage because of heavy costs involved and are not sustainable. Natural fortification of the common bean especially through agronomic or soil management approaches is cheaper, and is a more effective and sustainable approach since the crop is one of the principal grain legumes grown by small-scale, resource poor farmers for food and sale in many countries in sub-Saharan Africa. Africa is the second most important bean-producing region of the tropics after Latin America, where the crop originated. Common beans are world’s second most important legumes after soybeans. Beans are an important item in the diet because they are relatively inexpensive and highly nutritious; hence important to the poor as a source of dietary protein and minerals. They are rich in protein (20-25%), phosphorus, iron and vitamin B1. Beans are therefore a highly nutritious and a low-cost protein food. Given the widespread use of common beans worldwide, efforts to improve their protein, iron and zinc contents may benefit a great many people. Beans are primarily grown by small-scale, resource-poor farmers, mainly intercropped with maize, coffee, bananas, sorghum, millet, potatoes and / or cassava. Increasing productivity of beans in a sustainable manner by the small-scale and resource-poor farmers is an urgent and first priority. In addition, current bean lines in use have a suboptimal nutritional value, which has to be improved. Ways in which agriculture can contribute to finding sustainable solutions to food system failures should be considered through holistic food-based system approaches, thereby closely linking agricultural production to improving human health, livelihood and well-being. Such action will stimulate support for agricultural research in many developed countries because it addresses consumer issues as well as agricultural production issues. A concerted effort of testing various agricultural practices in their capacity to increase micronutrient density in staple foods grown in the field is required. Nitrogen has to be added to the soil either through industrial nitrogen fertilizers, or by transformation of atmospheric nitrogen into forms which plants can take up for protein synthesis. This latter form known as Biological Nitrogen Fixation (BNF) is accomplished by free living and symbiotic microorganisms endowed with the enzyme nitrogenase. It is not only economically sound, but also environmentally more acceptable than industrial N sources. The use of industrial N source is extensive in developed countries and minimal to non-existent in the developing world. Deficiency of soil nitrogen is the most serious constraint to bean production in Africa, with estimated losses of more than 389,900 t per year. At the same time, BNF technology is very advanced in developed countries while this vast potential has gone largely untapped in the developing countries, especially in the African continent. In fact several African countries do not undertake any BNF improvement work at all. The amount of biologically fixed nitrogen by legumes varies a great deal depending on the rhizobium strain, the cultivar of the host and the environmental conditions. However, the capacity of a legume to nodulate and fix nitrogen is genetically determined. This study aims at assessing the possibility of increasing iron and zinc concentrations in edible portions of beans as a suitable long-term solution, low-cost and sustainable option in reducing the effects of poor health caused by protein and micronutrient malnutrition among the poor especially in developing countries such as Kenya, and improving food security, production and quality of life. The study also seeks to assess variation in biological nitrogen fixation in bean genotypes and identify lines combining high mineral density with enhanced nitrogen fixation.
Overall objective
To determine the effect of plant growth promoting rhizobacteria (PGPR) and their interactions with applied molybdenum, basal nitrogen, phosphorus fertilization and environmental or soil-related factors on the genetic variation for N2 fixation and micronutrient concentration in common bean genotypes.
Specific objectives
1.Screen and characterize germplasm (collection including 1500 lines) for genetic variation in N2 fixation capacity and micronutrient concentration among the bush and climbing bean genotypes.
2.Identify and characterize local PGPR and determine their effect on N2 fixation and micronutrient concentration in a limited number of screened bean genotypes.
3.Determine the effect of available three commercial rhizobia strains on N2 fixation and micronutrient concentration in the screened bean genotypes.
4.Determine the effect of the interactions between the three commercial rhizobia strains x Mo, basal N and P on N2 fixation and micronutrient concentration.
5.Assess the influence of environment, moisture status, soil type and nutrient status on N2 fixation and micronutrient concentration.
6.Identify bush and climbing bean genotypes combining high N2 fixation capacity and micronutrient concentration.
7.Determine the mechanisms of uptake, mobilization and accumulation of iron and zinc in edible portions of beans from the growing media in the greenhouse.
8.Validate the performance of good N2 fixers and micronutrient-rich genotypes under a range of farmer conditions and in replicated trials across agro-ecological zones in Kenya.

Expected output:
1.Information on the genetic variation in nitrogen fixation capacity and micronutrient oncentration of the nutribean germplasm nursery will be obtained.
2.The role of the local PGPR in nitrogen fixation capacity and micronutrient concentration of the screened bush and climbing bean genotypes will be known.
3.The role of the three commercial rhizobia strains and their interactions with molybdenum, basal nitrogen and phosphorus fertilizer on the nitrogen fixation and nutritional quality of edible portions of beans will be established and documented.
4.A better understanding of the interactions between the studied bean genotypes and the mentioned soil fertility management practices under local (farmer) conditions will be established.
5.Information on the agronomic performance and yield of beans in the study sites, influence of environment, moisture status, soil type and fertility status will be generated, in relation with the environmental and soil data obtained from the respective sites.
6.Bean genotypes combining (1) higher nitrogen fixation capacity and (2) seed and leaf iron and zinc concentrations will be known. This will permit the selection of combinations of bean genotypes, microbial inocula and soil fertility management practices leading to improved nitrogen fixation, nutritional value and yield of beans.
7.The mechanisms of uptake, mobilization and accumulation of iron and zinc in edible portions of beans will be known and documented.
8.Performance of good nitrogen-fixers and micro nutrient-rich bean genotypes under farmer conditions and national performance trials across agro-ecological zones in Kenya will be validated.

Key words: Common bean, biological nitrogen fixation, nutritionally balanced food, diet, micronutrients, protein

Latest application date: 2009-12-31

Financing: iro-scholarship

Type of Position: scholarship

Source of Funding: IRO scholarship

Duration of the Project : 4 years


Research group: Department of Microbial and Molecular Systems (M#S)