Genetic improvement of rice for biotic and abiotic stress tolerance

Abstract

IntroductionRice (Oryza sativa L.) is one of the oldest cultivated crops. It has been cultivated in India and China for several thousands of years (Poehlman and Sleper, 1995). The major cultivated species of rice, Oryza sativa (2n = 2x = 24), originated in southern and southwestern tropical Asia. The other species of cultivated rice, Oryza glaberrima (2n = 2x = 24), is indigenous to the upper valley of the Niger River and it is cultivated only in western tropical Africa. Twenty-three species and 10 recognized genome types (AA, BB, CC, BBCC, CCDD, EE, FF, GG, HHJJ, and HHKK; Gramene: http://www.gramene.org/species/ oryza/rice_taxonomy.html) of Oryza are recognized. Close relatives of O. sativa are the wild perennial species O. rufipogon and the wild annual species O. nivara. Both are diploid weedy species with the AA genome.Rice is an important food crop and it needs continuous improvement due to the continuous increase in population. The major objectives to improve rice crops using biotechnological techniques include: 1) high yield potential, 2) early maturity, 3) resistance to lodging and shattering, 4) resistance to stress environments, 5) disease resistance, 6) insect resistance, 7) grain quality, and 8) enhancement of nutritional components. Economic importance of riceRice (Oryza sativa L.) is the most important crop of world. About 90% of the world's rice is grown in China, India, Pakistan, Japan, Korea, Southeast Asia, and other adjacent areas (USDA, 2014). Outside of Asia, Brazil and the United States produce the largest amounts of rice (Poehlman and Sleper, 1995). Rice is the staple food for over one-half of the world's people (FAO, 2008). In Pakistan, rice is a highly valued food crop and it is also a major export item. It accounts for 3.2% of the total value added in agriculture and 0.7% of the GDP. Area sown for rice is estimated at 2.891 × 10 6 ha and the production was 7.005 × 10 6 t in -2015 (Ministry of Finance, 2015. Rice is cultivated in diversified climatic conditions of Pakistan. Basmati rice (Indica) is grown in the traditional rice-growing belt of Punjab Province. In Swat, in high altitude alpine valleys, temperate Japonica rice is grown. In the south of Khyber Pakhtunkhwa, Sindh and Baluchistan provinces, IRRItype long-grain heat-tolerant tropical rice is mainly grown. Transformation of rice cropsThe world will need about 25% more rice by the year 2030 to meet the estimated demand of an increasing global population (Wani and Sah, 2014). One way to meet this challenge is to grow rice on more area, which is difficult due to increasing urbanization and escalating population in Abstract: Rice (Oryza sativa L.) is among the most important food crops that provide a staple food for nearly half of the world's population. Rice crops are prone to various types of stresses, both biotic and abiotic. Biotic stresses include insect pests, fungus, bacteria, viruses, and herbicide toxicity. Among abiotic stresses, drought, cold, and salinity are also well studied in rice. Various genes have been identified,...

Traits association and path coefficient analysis of yield and related traits in rainfed lowland rice (Oryza sativa L.) genotypes in North Western Ethiopia

“…The major cultivated species of rice, Oryza sativa (2n=2x=24), originated in Southern and South Western Tropical Asia. The other species of cultivated rice, Oryza glaberrima (2n=2x=24) is indigenous to the upper valley of the Niger River and it is cultivated only in Western Tropical Africa (Ansari et al, 2015). Rice provides the two-thirds of calories intake for more than three billion people in Asia and one-third of calories intake of nearly 1.5 billion people in Africa and Latin America (Khan et al, 2015).…”

Genetic Variability, Heritability and Genetic Advance for Yield and its Related Traits in Rainfed Lowland Rice (Oryza sativa L.) Genotypes at Fogera and Pawe, Ethiopia

“…The river valleys of Yangtze, Mekon River area in China could be the primary center of origin of Oriza sativa [3,4]. Oryza glaberrima is indigenous to the upper valley of the Niger River and it is cultivated only in western tropical Africa [5].…”

Molecular Control and Application of Male Fertility for Two-Line Hybrid Rice Breeding

“…Over time, the tremendous progress in the form of hybrid-breeding technology greatly benefited agriculture by HR with high yield and better tolerance against stressors (e.g., biotic stresses as the diseases, pests, and pathogen infestation and abiotic stresses as the drought, heat, salt, etc.) as compared to the inbred lines/varieties [ 4 , 19 , 20 , 21 ]. Rice is a self-pollinated cereal crop; its male fertility (MF, described as the release of the workable gametes or functional pollens that can fertilize female gametes) control demands the male sterility system to generate HR lines/varieties.…”