CHAPTER ONE

INTRODUCTION

1.1. Background of Study

Common bean (Phaseolus vulgaris L.) belongs to the family Fabacea and originated from Central and South America. It is now widely cultivated as a major food crop in many tropical and subtropical areas of America, Europe, Africa and Asia (Wortmann, 2006). It is highly polymorphic warm-season, herbaceous annual crop and which has two growth habit: erect herbaceous bushes (determinate), up to 20-60 cm high; and twining, climbing vines (indeterminate) up to 2-5 m long (Ecocrop, 2013).

Common bean is a major grain legume consumed worldwide for its edible seeds and pods. In Cameroon, it is an important cash crops and source of protein in many Western regions. It is high in starch, dietary fiber and is an excellent source of potassium, selenium, molybdenum, thiamine, vitamin B6, and folic acid (Maiti, and Singh, 2007). It is used as food in different form the green unripe pods are cooked or conserved as vegetable and the ripe seeds cooked for “cornchaff” boiled and mixed with maize, also pounded with potatoes ” pounding pounding”, fried and eaten with ‘puff- puff’ ‘ nchombo’

They World production of common bean exceed more than 25 million MT, out of which about 6million MT is produced in Africa (FAOSTAT, 2015). In Cameroon it is widely grown as traditional pulse crop with area of about 165,000 hectares and total annual production of 195,111 metric tons(FAO 2021) .In terms of geographical distribution of production, North West took the lion share (35%) of common bean production in the country, followed by West (25%), Adamawa(15%), North region (10%) and the remaining 15,% goes to small holders farmers (CSA 2023).

However, common bean production is being effected by a variety of biotic and abiotic stresses. Two important factors that can influence bean yields are the presence of Rhizobium bacteria that form root nodules and fix atmospheric nitrogen, and the occurrence of angular leaf spot disease caused by the fungus Pseudocercospora griseola.

Rhizobium inoculation has been shown to significantly increase bean yields by improving the plant’s access to fixed nitrogen (Hungria et al., 1997). However, the degree of yield response can vary depending on factors like native Rhizobium populations, soil fertility, and environmental conditions. Similarly, angular leaf spot can cause substantial defoliation and yield losses if not properly managed (Navarrete-Maya et al., 2002), but the impact may depend on factors like disease severity and timing of infection.

This study aims to evaluate the interactive effects of Rhizobium inoculation and angular leaf spot occurrence on the yield and productivity of common bean cultivars under field conditions. Understanding these interactions is important for developing integrated management strategies to optimize bean production. The results will provide insights into the relative importance of biological nitrogen fixation and disease resistance for improving common bean yields.

1.2. Problem Statement

The importance of Beans and its production to the population of Bamenda.The productivity of common beans (Phaseolus vulgaris) is often constrained by various biotic and abiotic factors, including the occurrence of angular leaf spots (ALS) and the availability of effective Rhizobium bacteria for biological nitrogen fixation. Angular leaf spot, caused by the fungal pathogen Phaeoisariopsis griseola, can significantly reduce bean yields if left unmanaged. On the other hand, the symbiotic relationship between Rhizobium bacteria and bean plants can enhance the plant’s access to atmospheric nitrogen, potentially increasing growth and yield.

1.3. Justification of the Study

A lot of research has being done to solve this problem Despite all research carried out to evaluate the effect of Rhizobium inoculation and occurrence of angular leaf spots on the yield of common beans, there is still a huge gab in Cameroon as yields are extremely low as compared to developed world or the world’s production. The low yields of common beans might merely reflect the inability of the current technology to overcome soil and environmental constraints due to inability in the proper application of fungicide and how to increase nitrogen fixation capacity in plant. The use of synthetic fertilizer and fungicide on common beans is becoming rampart to the environment, human health, water bodies and the ecosystem as a whole. With all these demerits, the use of Rhizobium japonicum will be of promising output.

1.4. Significance of the study

Nowadays, agricultural intensification is taking interest on environmentally sustainable approaches, these perspective modifies the agro-ecosystem to minimize the used of synthetic input (pesticide) and maintain economic profitability with biocontrol agents such as native beneficial microbiota which will increased production yield and keep the human health and environment healthy

1.5.1. Main Research Question

Can Rhizobium japonicum inoculation impact the occurrence of angular leaf spot and the yield of common bean?

1.5.2. Specific Research Question

• Can Rhizobium japonicum inoculation effect the occurrence of angular leaf spot disease in common bean?
• Can the so-called local Rhizobium strain impact the yield of common bean under severe disease outbreak?

1.6. Objectives of the Study

1.6.1. Main Objective

This research aimed to evaluate the effect of Rhizobium japonicum inoculation on the occurrence of angular leaf spots on the yield of common beans.

1.6.2. Specific Objectives

This work aimed specificallt to;

• Asess the ability of Rhizobium japonicum inoculation to supress the angular leaf spot disease in common bean
• Evaluate the impact of Rhizobium inoculation on the yield of common bean under severe Angular leaf spot outbreak?