Genetics Plants

Introduction To LEGUMES

Legumes are the most diverse plants on earth widespread in tropics and temperate zones. Legumes can grow in much degraded soil because they have the ability to fix nitrogen in association with the Rhizobium. Besides its major role in traditional diets throughout the world, Legumes provide a multiple benefit to both soil and other crops and through intercropping. Nitrogen is the most limiting nutrient for growth of leguminous plants like common beans, soya-beans, cowpeas and garden peas because that present in the soil cannot support the growth. An Endophyte is an endosymbiont often a bacterium or fungus, which lives within a plant for at least part of its life cycle without causing apparent disease. Endophytes may be transmitted either vertically (directly from parent to offspring) or horizontally (among individuals). Endophytes and plant often engage in mutualism with endophytes primarily aiding in health and survival of the host plant. Endophytic associations date back to the first land plants. Endophytic populations like rhizospheric  populations are conditioned by biotic and abiotic factors but endophytic bacteria could be protected from biotic and abiotic stresses than rhizospheric bacteria . Endophytic bacteria in a single plant host are not restricted to a single species but comprise several genera and species. No one knows if communities inside plants interact, and it has been speculated that beneficial effects are the combined effect of their activities. In this review, we will first address the diversity of endophytes. Unfortunately, some of the older papers describing bacteria inside plants have used methods that do not allow an accurate classification of endophytic bacteria.  Criterion to recognize the “true” endophytic bacteria have been published and this requires not only the isolation from surface-disinfected tissues but also microscopic evidence to visualize “tagged” bacteria inside plant tissues. Use of the term putative endophytes has been recommended for those not validated microscopically. True endophytes may also be recognized by their capacity to re-infect disinfected seedlings. In a process guided by both the bacteria and plant, the rhizobia invade a plant tissue and ultimately inhabit individual plant cells within the host roots. Once inside the plant the rhizobia can become efficient symbionts breaking down nitrogen (N₂) from air pockets in the soil into forms that are useful for the plant.

      PGPR is an important constituent of agricultural systems which in turns depends largely on the beneficial microorganisms present in rhizosphere and helps crops to maintain growth and sustain productivity (Rosas et al.2009). Solubilizing inorganic phosphates by biological nitrogen fixation control of plant pathogens via a synthesis of antibiotics, by nutrient cycling and by seedling establishment.

   Chickpea (Cicer arietinum) is a leguminous plant. Chickpea is considered less labor-intensive crop and its production requires less external inputs as compared to cereals. Chickpea is widely grown around the world and serves as a multi-use crop. It plays a significant role in improving soil fertility by fixing the atmospheric nitrogen. It can fix up to 140 kg N ha^-1 from air and meet most of its nitrogen requirement. After harvest, it leaves substantial amount of residual nitrogen for subsequent crops and adds some amount of organic matter to maintain and improve soil health and fertility. This saves the fertilizer input cost not only for chickpea but also for the subsequent crops. Chickpea has the ability to grow on residual moisture which gives farmers the opportunity to engage in double cropping, where chickpea is sown at the end of the rainy season following the harvest of the main crop. This allows more intensive and productive use of land, particularly in areas where land is scarce. It is also an excellent source of protein, fiber, complex carbohydrates, vitamins, and minerals thus can help alleviating malnutrition and improving human health. The growing demand in both the domestic and export markets provides a source of cash for smallholder producers. It has deep tap root system, chickpea can withstand drought conditions by extracting water from deeper soil layers. It also increases livestock productivity as the residue is rich in digestible crude protein content compared to cereals. Chickpea was first produced in the Middle East about 7,000 years ago. At present, it is produced in over 40 countries represented in all continents. However, the most important chickpea producing countries are India, Turkey, Pakistan, Iran, Mexico, Australia, Ethiopia, Myanmar, and Canada. Chickpea is currently grown on about 11 million hectares worldwide with 65% and 8% share belonging to India and Pakistan, respectively. Average annual production of chickpea is about 9 million tonnes with 95% of chickpea cultivation and consumption occurring in the developing countries.