Sweet Sorghum: Salt Tolerance and High Biomass Sugar Crop

Soil salinity is one of the main problems for plant growth in agriculture, especially in countries where crops should be irrigated (Ahloowalia et al., 2004). Soil salinity has been considered a limiting factor to crop production in arid and semi arid regions of the world (Munns, 2002). Saline soils are estimated about 5 – 10% of the world’s arable land (Szabolcs, 1994), and the area affected by salinity is increasing steadily (Ghassemi et al., 1995). Saltaffected soils are distributed throughout the world and no continent is free from the problem (Brandy and Weil, 2002). Globally, a total land area of 831 million hectares is saltaffected (Kinfemichael & Melkamu, 2008; FAO, 2000). However, soil salt accumulation can change with time and place, as a function of soil management, water quality (Almodares & Sharif, 2005), irrigation method, and the weather conditions. Salt accumulation is mainly related to a dry climate, salt-rich parent materials of soil formation, insufficient drainage and saline groundwater or irrigation water (Almodares et al., 2008a). Salts in soils are chlorides and sulfates of sodium, calcium, magnesium, and potassium that among them sodium chloride has the highest negative effect on the plant growth and development. Salinity causes slow seed germination, sudden wilting, and reduce growth, marginal burn on leaves, leaf yellowing, leaf fall, restricted root development, and finally death of plants. The inhibitory effects of salinity on plant growth include: (1) ion toxicity (2) osmotic influence (3) nutritional imbalance leading to reduction in photosynthetic efficiency and other physiological disorders. Among agricultural crops, sorghum (Sorghum bicolor L. Moench) is naturally drought and salt-tolerant crop that can produce high biomass yields with low input. Also, it can thrive in places that do not support corn, sugarcane and other food crops. In addition, sweet sorghum has potential uses (six F) such as: food (grain), feed (grain and biomass), fuel (ethanol production), fiber (paper), fermentation (methane production) and fertilizer (utilization of organic byproducts), thus it is an important crop in semi-aired and aired regions of the world. Sorghum is grown on approximately 44 million hectares in 99 countries (ICRISAT, 2009). An estimation of the world-wide tonnage produced in 2007-2008 is shown in Table 1. The increasing cost of energy and deplete oil and gas reserves has created a need for alternative fuels from renewable sources. The consumption of biofule may reduce greenhouse gases. Also it can be replaced with lead tetraethyl or MTBE (Methyl tert-butyl ether) that are air and underground water pollutants,