CHAPTER 1
INTRODUCTION
1.1 Research background
Rice is an oldest crop plant and cultivated since ancient time. It belongs to the grass family (Germineae) and genus is Oryza. The genus Oryza consists of 21 wild and two cultivated species Oryza sativa and Oryza glaberrima Oryza sativa are widely cultivated in Asia, America and Europe. The subspecies Indica and Japonica are further classified into temperate (Japonica), tropical (Japonica), indica (Indica) and aus (Indica). The two subspecies of Oryza sativa are Indica and japonica comprised most varieties of rice and based on morphological and physiological traits, many of rice varieties can be placed in these two rice races (Oka, 2012).
Rice (Oryza sativa) is a very important staple food for
The iron stress causes the inhibition of seed germination, typical leaf-bronzing symptoms, stain, edges and poorly developed dark brown root system. The reduction in height and dry matter has a related with rice production and ultimately affect the rice yield. Fe2+ toxicity has been reported in many Asian countries, including, Malaysia, Indonesia, Thailand, China, Philippines and India, there rice production are reduced by 12-100% depending rice cultivars tolerance to Fe2+ and on the toxicity severity (Audebert and Sahrawat, 2000).
Aluminum (Al) when combines with acid soils, very toxic to the crop root system and ultimately a reduction in vegetative growth that resulting the lower crop production (Kochian, 1995). It is reported that from a total of 41,274,890 Km2 of potentially cultivated land, 19,863,000 Km2 or approximately half are influenced by Al3+ toxicity (Bot et al., 2000). Crop production in acid soil is reduced by 25-80% where Al3+ toxicity is limiting factor influencing crop production in acidic soil (Herrera-Estrella,