الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Rice (Oryza sativa L.) is the most important food crop and a primary food source for more than 50% of the world population (Khush and Virk, 2000). It is providing a stable diet for most of the world’s population (Xing et al., 2004). It is also one of the most versatile and important cereal crops of Poaceae family cultivated for more than 10.000 years (Sasaki, 2005). In Egypt, rice is the most important summer crop occupying almost 1/3 of the cultivated area (1.88 million feddans), USDA (2014). Farmers grow rice for several vital purposes including nutrition, as cash crop and for ameliorating soil chemical disorders especially salinity. In spite of the governmental decrees and regulation issued to regulate the acreage cultivated with rice, farmers insist to cultivate that crop to fulfill the previously mentioned purposes. Irrigated rice requires a large quantity of water. It is a highly– consuming crop for irrigation water, where water requirements range from 6000 to 8000 m3/ faddan, according to soil type, cultivar and environmental conditions and it needs about 3,000–5,000 L of water to produce 1 kg of grain (Bouman et al., 2007). Thus, rice consumes a large portion of Egypt’s total share of the Nile water (55 billion m3). Due to increasing limitations on water supply for agriculture, rice production, under reduced irrigation supply, is becoming a necessity in Egypt, as well as in many areas worldwide. This reduction in the amount of water, devoted to rice irrigation, imposes unprecedented stress on this crop. Stress causes severe yield loss (Wang et al., 2008). Drought stress is the major constraint to rice production and yield stability in the rainfed regions (Evenson et al., 1996).Water scarcity in agricultural production is becoming a serious worldwide issue. It has been widely accepted that new crop cultivars with high potential of strong drought tolerance can solve or improve this problem (Geng et al., 2008). Development of drought- tolerant lines of rice is the urgent need in the present scenario of limited water resources, irregular rains and water scarcity (Islam et al., 2012). Breeding for water stress tolerance by traditional methods is a time consuming path with many limitations (Dorffling et al., 1993). Conventional breeding has not proved satisfactory in this endeavor. Development of drought- tolerant lines, through the use of biotechnology approaches, would be appropriate, especially in high yielding variety background, by blending yield and drought tolerance appropriately. Anther culture has been quiet useful for the introgression of desirable traits, in overcoming sterility for the production of homozygous doubled haploid lines and for the utilization of heterosis in rice (Raina and Irfan, 1997). Therefore, anther culture would be of significant importance, especially when crossings are made among the upland rice genotypes (drought- tolerant) and Egyptian (drought sensitive) varieties. Anther culture is a useful technique in plant breeding, which allows the development of homozygous plant lines. Regeneration of haploid plants from 2 microspores in the anthers, and the subsequent chromosome doubling of the haploids results in fully homozygous diploids. Therefore, anther culture facilitates the immediate conversion of heterozygous breeding material to homozygous breeding material, which is a faster alternative to conventional inbred line development. In rice, haploid plant production by anther culture is accomplished in two steps. First, induction of a callus from the cultured anther followed by regeneration of plants from induced callus tissue. For the technique to be practical, these two in vitro events must occur efficiently and reliably in rice varieties (Mayakaduwa and Silva, 2017).