Soybean has been adapted and commercially cultivated in Madhya Pradesh, Maharashtra, Rajasthan, Karnataka and Andhra Pradesh. At present, it has been established as a most important oilseed crop of India in general and Madhya Pradesh in particular. Soybean (Glycine max (L.) Merrill) ranks first among the oil seed crops in the India as well as in the world.

Soybean has unprecedented expansion in India by recording 15-20% annual growth rate. It has emerged very fast since early eighty’s and occupied vital place in agriculture, edible oil economy, foreign exchange and enlistment of soybean farmers. It contributes around 25% of total edible oil pool of the country.

In India, in the year 2011-12, soybean cultivation reached 103 lakh hectares recording production of 119 lakh tonnes with an average of 1155 kg/ha. In Madhya Pradesh in the year 2011-12, area production and productivity was 57.0 lakh hectare, 62 lakh tonnes, 1077 kg/ha respectively. The present yield level is quite low in comparison to world’s average i.e. 22 q/ha. Among the major constraints, the erratic monsoon and climate change adversely affect the productivity. The soybean is covering vast area representing varied eco-edaphic conditions. Plants are subjected to a range of abiotic stresses that affect the growth and development adversely. Being a rainfed crop, soybean faces unpredictable moisture stresses either excess or scarce.

Soybean is a kharif crop and planting time is from mid June to mid July but due to climate change unpredicted rainfall occurs sooner or later. Either heavy rainfall damages crop at seedling stage or late rainfall creates water deficit (drought) at flowering and pod filling stages of soybean. Occasional exposure to both the types of stresses during same crop cycle, i.e. excess moisture at seedling, vegetative stage and drought during flowering and pod filling stage is common. Therefore, there is need of development of tolerant soybean genotypes for excess moisture stress and water deficit (drought) conditions.

Soybean is very sensitive to excess water as compared to other crops. Soybeans can survive underwater for a week or more under ideal conditions. Generally, soybeans tolerate 48 hours under water quite well but flooding for 4 to 6 days can reduce stands, vigour and eventually seed yield (Scott et al., 1989). Water logging tolerance was assessed in cultivars at early vegetative stages and early reproductive stages and results indicate the most susceptibility to excess water at the growth stages. Physiological characters including leaf water use efficiency were promising indicators for screening soybean which is tolerant to excess water conditions (Lee et al., 2004).

Although all higher plants require access to free water, excess water in the root environment of land plants can be injurious or even lethal because it blocks the transfer of oxygen and other gases between the soil and the atmosphere. Crop plants require a free exchange of atmospheric gases for photosynthesis and respiration; plants can be easily suffocated if this gas exchange is impeded. Oxygen status of cells and tissues varies significantly during ontogenesis and depends on environmental oxygen supply. The most common impediment to gas diffusion is water that saturates the root environment in poorly drained soils or that accumulates above soil capacity as a result of the overflow of rivers, excessive rainfall or excessive irrigation (Sairam et al., 2008). Growth is greatly inhibited in the deficiency (hypoxia) or complete absence (anoxia) of oxygen. In water-saturated soils roots grow only in a small region near the surface and do not exploit a large soil volume as they would under aerated conditions. Plants invariably wilt within few hours to 2-4 days of imposing a flooding stress (Jackson & Drew, 1984). Water logging to 8 days caused significant increase in O₂^- and H₂O₂ contents, and the values were 80–90% of the control values more. Gene expression studies showed enhanced expression of cytosolic-Cu/Zn-superoxide dismutase (SOD) and cytosolic-ascorbate peroxidase (APX) in the roots of waterlogged (Sairam et al., 2011). Water logging is also known to induce adverse effects on several physiological and biochemical processes of plants by creating deficiency of essential nutrients like nitrogen, magnesium, potassium, calcium. Apart from these Water logging induced alterations in physiological mechanisms, plants growing under flooded conditions also exhibit certain morphological changes entailing the formation of adventitious roots, initiation of hypertrophied lenticels and/or establishment of aerenchyma (Muhammad, 2012).

Water logging resulted in decrease in relative water content (RWC), membrane stability index (MSI) in root and leaf tissues, and chlorophyll (Chl) content in leaves, while the Chl a/b ratio increased (Sairam et al., 2009). Although water logging caused decline in total, non-reducing sugars and activity of alcohol dehydrogenase (ADH) increased up to 8 days of water logging (Sairam et al., 2009). Water logging tolerant genotypes depend on the availability of sufficient sugar reserve in the roots, activity of sucrose synthase to provide reducing sugars for glycolytic activity and ADH for the recycling of NADH for the continuation of glycolysis, the major source of energy under hypoxia. This was reflected in better RWC and Chl content in leaves, and membrane stability of leaf and root tissue (Kumutha et al., 2008). Soybean dry matter and nitrogen were determined at various times following the initiation of flood or low O₂ treatment. N₂ fixation was more sensitive to flooding than was biomass accumulation. The decrease in N₂ fixation occurred faster (within 7 days of flooding) than decrease in biomass (within 14-21 days) and the decrease in N₂ fixation was more pronounced than the decrease in biomass (Bacanamwo & Purcell, 1999). According to Turner et al. (2013), there is very low auxin activity during soybean nodule initiation, hypersensitivity to auxin inhibits nodule development and a regulatory feedback loop involving auxin and cytokinin is crucial for proper nodule development in soybean. Soybean management system influenced development of the different yield components and produced seed mass ranging from 10.5 to 16.5 g 100 seed^-1, seed number from 2878 to 3824 seeds m^-2, pod number from 1182 to 1571 pods m^-2, seeds per pod from 2.36 to 2.49 seeds pod^-1. Harvest index ranged from 56.2-58.0% across management systems as reported by Pedersen & Lauer (2004).

The experiments were conducted at the Department of Plant Breeding and Genetics, Jawaharlal Nehru Agricultural University in Jabalpur, MP in collaboration with Japan International Cooperation Agency (JICA), College of Agriculture Indore, Indore, MP. The plot size of each genotype was 3.6 m² (2m x 1.8m). There were four rows in each plot; row to row spacing was 45cm and plant to plant spacing 6.25 cm. Plant population of 128 plants per plot was maintained.

Thirty two plants were maintained in each row (2 meter). The statistical analysis was done using Factorial Randomized Block Design (FRBD) with three replications. Sowing was completed on 6^th July 2012. A total of 25 soybean cultivars and lines were exposed to EMS condition at 15-20 DAS, 35-40 DAS and 55-60 DAS (Seedling, vegetative, reproductive and pod filling stage). As the control, the same set of soybean genotypes were grown in a well drained field condition with general cultivation practices. Soil moisture percentage was calculated at 30 DAS, 60 DAS and 90 DAS (Black, 1965). Metrological Observations were collected from Agro-metrological Department JNKVV-Jabalpur (M.P.) (Table 1 and Plate 1234).

The present experiments illustrated evaluation of 25 soybean cultivars and lines grown under two conditions i.e. control (non-flooded) and Excessive moisture (flooded field). On the basis of yield performance evaluated soybean tolerant cultivars and lines. Excessive moisture, tolerant cultivars and lines produced more pods plant^-1, number of seeds plant^-1 and heavier seed weight and higher yield. On the basis of yield performance the popular cultivars and advanced lines Bragg, JS 97-52 and JS20-87, JS20-71 showed higher yield up to some extent, under excessive moisture stress as well as control condition respectively.

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