CHARACTERIZATION OF MESORHIZOBIUM SP: INTRODUCTION

INTRODUCTION

The earth’s population grows annually by 1.4% and is expected to double in the next fifty years. This increase in population necessitates a simultaneous enhance in food production to maintain the dietary intake of the growing human population in an environmentally sustainable manner. This demand for higher crop production also implies a higher demand for fixed nitrogen (Graham & Vance,2000). Chemically produced nitrogen fertilizers can provide this nitrogen, but they are expensive to produce in addition to being harmful to the environment. This damage to the environment includes changes in the global nitrogen cycle, loss of nitrous oxides to the atmosphere, acid rain, nitrate pollution of ground water & induced leaching of soil nutrients. An inexpensive & environmentally friendly alternative to nitrogen fertilizer is biological nitrogen fixation (BNF), which is a process where by nitrogen gas in the atmosphere is converted into biologically useful & utilizable source of nitrogen for plants. The majority of the world’s land based biological nitrogen fixation can be accounted for by the symbiotic nitrogen fixation relationship between leguminous plants & rhizobia. The advantages of this type of BNF have led to numerous studies investigating the diversity & identity of the associated bacterial symbionts.

Although symbiotic nitrogen fixation by legumes is generally the dominant source of nitrogen input in soil for imparting fertility but soil stresses, pose a severe yield constraint in obtaining plant growth and development (Lawson et al, 1995). Environmental stresses adversely affect symbiotic nitrogen fixation in both tropical and temperate soils (Graham, 1981). Limiting rhizobial survival and persistence in soils and reduce nodulation.Typical environmental stress faced by the legume nodules & the symbiotic partners may include water stress, salinity, soil pH, temperature, heavy metals, fungicides etc (Kucuk & Kinvanc,2008).

This study determines the diversity of the Mesorhizobium that nodulates Chick pea through their growth characteristics, salt and ph tolerance, intrinsic antibiotic resistance, carbon source utilization and fungicide resistance pattern. This could lead to an improvement in the selection of isolates adapted to the climatic conditions.

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