EFFECT OF RHIZOBIUM ON GROWTH OF DIFFERENT MUNGBEAN VARIETIES UNDER SALT STRESS CONDITIONS

Excessive and imbalanced use of chemical fertilizers may pose devastating effect on soil fertility and sustainable productivity. Bio-organic amendments improve soil fertility and sustainable crop productivity. Seeds of mungbean varieties i.e. NCM-2013, Chackwal-Mung 06, NM-11 and AZRI-06 were inoculated with rhizobium in saline soil. These inccilated miunngbean varieties were sown under artificially salinity developed soil (ECe= 5.0 dSm -1 ) using completely randomized design with three repeats for enhancement of growth. The experiment was conducted during July to September, 2015 in the Head House of Land Resources Research Institute, National Agricultural research Centre, Islamabad, Pakistan. Data were collected on germination, plant height, root length, fresh / dry weight and chlorophyll contents during experiment period. Ionic concentrations of P, Cu, Fe, Mg and Zn were determined to compare the difference of edible quality in saline soil under the inoculation of seeds with rhizobium. Effect of biozote on germination, root length, fresh weight and dry weight was significant in all mung bean varieties: NCM-2013, Chakwal Mung-06, NM-II and AZRI-06 under salt stress conditions. Maximum germination (53%) was recorded by Chakwal Mung-06 followed by 51% by AZRI-06. The maximum root length (10.1 cm) was registered by NM-II. Fresh weight / plant was maximum (5.1 g) by AZRI-06. The maximum dry weight/plant (1.5 g) was recorded by AZRI-06. Maximum P% (0.14), Cu (4.83 ppm), Fe (179.3ppm), Mg (2.07ppm) and Zn (168.8ppm) of Chakwal Mung-06 with the use of rhizobium under salt stress by NM-11. Similar trend was also recorded in ionic concentration of P, Cu, Fe and Mg by NM-11 without rhizobium under salt stress conditions.. The saline soil affected the quality of mungbean showing the reduction under salt stress without rhizobium inoculation in ionic concentration. The results of ionic values showed that NM-11 attained the highest position following the AZRI-06. [3] and [8] reported same results regarding K and P of different crops under salt stress conditions. Key Words--Mungbean varieties, saline soil, rhizobiumgrowth, edible quality and ionic concentration


INTRODUCTION
Biofertilizers are known to play an important role in increasing biological fixation of atmospheric nitrogen and enhance phosphorus availability to crop (Bhat et al., 2013). Similarly humus derived from vermicompost is most commonly used for sustainable production (Premsekhar and Rajashree 2009) due to its beneficial effects on nutrient uptake and retention, pest control and productivity (Barrios et al., 2011).
Mungbean is a very important pulse crop which provides an inexpensive source of vegetable dietary protein. In Pakistan, mungbean is cultivated on an area of 127.7 thousand hectares with total grain production of 98.7 thousand tons Economic survey of Pakistan, 15). It is popular for its nutritive value and digestibility, containing higher protein contents (30%), fat (1.2%), carbohydrates (65%) and essential macronutrients like Phosphorus 340 mg 100 g -1 and Calcium 118 mg 100 g -1 (Anwar et al., 2007). It can be cultivated during spring and winter and takes less time to mature and fits well in existing cropping pattern of the country. Today, of various abiotic stresses, soil salinity is known to cause considerable crop losses (Ashraf et al., 2008). Although soil salinity occurs predominantly in arid and semiarid regions, it has been found in all the climatic zones (Munns, 2008). Moreover, the problem in salt affected land is increasing due to low quality water usage for irrigation, improper drainage in canal-irrigated wetland agro-ecosystems, entry of seawater in coastal areas during cyclones, and higher accumulation of salts in the root zone due to considerable evaporation of water and insufficient leaching of ions due to low rainfall in arid and semi-arid regions (Munns, 2008). According to an estimate, 33% of irrigated land world-wide has been affected by salinity (Ashraf et al., 2008). Pakistan is worst hit by soil salinity as about 14% of total irrigated land in Pakistan is salt affected (Economic Survey of Pakistan, 2008). Salt affected soils are generally categorized as saline, sodic, or saline-sodic. In other words, a soil is considered to be saline when electrical conductivity of saturate soil pastes is equal or greater than ~4 dS m-1 at 25°C (equivalent to ~40 mM NaCl) and the sodium adsorption ratio (SAR) is ~13-15 (Munns, 2008).
Inside the plant, soluble salts at higher concentrations cause hyperosmolality, ion toxicity and disequilibrium of nutrients that adversely affect plant growth and development (Munns, 2008). High levels of both Na+ and Cl-in cytosol are inhibitory to a number of metabolic and cellular processes (Ashraf, 2009).
Soil salinity causes prominent losses of yield in all crops, therefore causing to reduction in crop production (Ashraf,. 2009 and The conductance of such experiments has resulted in a substantial increase in both growth and yield of many crops grown under saline conditions (Ashraf,. 2009 and Cha-um. et al., 2011)Exogenous application of inorganic essential nutrients as foliar spray or through the root growing medium has also been reported to be an economical and efficient means of mitigating the adverse effects of salt stress on different crops (Ashraf,. 2009 andKaya . et al., 2010) of different major essential nutrients, potassium (K) and phosphorus (P) play vital roles in plant growth and regulate various metabolic reactions (Taiz and Zeigr, 2010).. Therefore this study was carried out to evaluate the performance of mungbean varieties under saline condition for the enhancement of pulse production under marginal lands.

MATARIALS AND METHODS
Seeds of mungbean varieties i.e. NCM-2013, Chackwal-Mung 06, NM-11 and AZRI-06 were inoculated with rhizobium in saline soil. These inccilated miunngbean varieties were sown under artificially salinity developed soil (ECe= 5.0 dSm -1 ) using completely randomized design with three repeats for enhancement of growth. The experiment was conducted during July to September, 2015 in the Head House of Land Resources Research Institute, National Agricultural research Centre, Islamabad, Pakistan. Data were collected on germination, plant height, root length, fresh / dry weight and chlorophyll contents during experiment period. Ionic concentrations of P, Cu, Fe, Mg and Zn were determined to compare the difference of edible quality in saline soil under the inoculation of seeds with rhizobium. The data collected were analyzed statistically according to the procedure given using statistic, 2000 package and means between treatments were compared using LSD test at 5% probability level ( Steel and Torrie, 1997)