Review on the Effect of Seed Source and Size on Grain Yield of Bread Wheat (Tritium Aestivum L.)

Wheat (Tritium aestivum L.) is the most important crop and among the major three cereal crops that provides 20 percent of the total energy requirement in human food. It is a major crop contributing importantly to the nutrient supply of the global population and has the highest content of protein of all the staple cereals and contains essential minerals, vitamins, and lipids. It shows wide adaptation to diverse agro-ecological conditions and cropping technologies. The productivity of the crop remains low (2.4 tons ha-1) in the Ethiopia as compared to the world average yield (3.19 tons ha -1). The low yield per hectare is attributed to many factors, such as seed source, unavailability of quality seed, use of poor quality seeds, inappropriate seed size and seed rate are some of the factors. Seed source influenced growth and yield during the growing season but the response depended on seed size and variety. Seed quality is very important to optimum growth and yield production in farm which influenced by many factors such as genetic characteristics, viability, germination percent, vigor, moisture content, storage conditions, survival ability and seed health. High quality seed is important to ensure maximum seed germination and seedling vigor, which is turn is instrumental in achieving maximum yield. poorer quality seeds show low viability, reduced germination and emergence rates, poor tolerance to sub optimal conditions and low seedling growth rates. The seed quality is also reflected in the final growth, maturity of plants, their uniformity and stability of yield. Seed size is an important physical indicator of seed related to yield, market grade factors and harvest efficiency. Seed size was the trait that was most consistently associated with yields. Seed size was the most consistent seed trait that influenced growth and yield. Grain yield of wheat significantly increased by increasing seed size. The use of high quality seed and large seed size increase the grain yield of bread wheat.