Introductory Chapter: Recent Advances in Rice Biotechnology for Abiotic Stress Tolerance

*Munazza Ijaz, Roshina Shahzadi, Akmaral U. Issayeva, Shazia Anwer Bukhari and Mahmood-ur-Rahman*

### **1. Introduction**

The world population is rising gradually, and it would be approximately 9.1 billion in 2050 but the production of agriculture is not escalating with this speed. The global production of agriculture should be increased up to 100-110 percent till 2050 to feed the whole population. Moreover, agricultural production and crop growth are negatively affected by abiotic stresses. So, it is a major hurdle in the way of increasing food production world-wide. The drought, heat, cold, salinity, ultra violet radiations and heavy metal toxicity are the major abiotic stresses that affect the crop yield. The significant source of calories for human beings is cereals. The maize, wheat and rice produce 10%, 17% and 23% respectively. *Oryza sativa* (rice) serve as a staple food and a famous cost-effective cereal. Acceptance of green revolution cultivars lead towards an essential revolution in the production of rice [1]. First green revolution came into being by producing high-yielding semi dwarf rice and wheat cultivars via plant breeding and providing high doses of nitrogen fertilizers. It helped in preventing the famine in semi-arid regions of Southern Asia [2].

The first transgenic rice was developed almost two decades before that initiated the high-throughput transformation protocols for the development of high yielding cultivars and it laid the foundation of transgenic rice biotechnology [3]. After the genome sequencing of rice, the development of transgenic rice varieties for better stress tolerance, high yield and better nutritional qualities became relatively easy and gained more importance. Similarly, the donor genes from the other species (like bacteria, fungi, viruses, animals and insects) can be inserted in the rice for obtaining the improved cultivars for making agriculture more sustainable. Improvement of some other significant traits (like photosynthetic rate, aroma and nutrition of rice grains) with the good stress tolerance has gained attention in past few years [2]. Some examples of these traits will be discussed in the next sections comprehensively.

The transgenic or genetically improved crops are an integral part of the agriculture industry in the modern world. The transgenic cereal crops have been commercialized and cultivated by more than twenty-eight countries. In 1996, only 1.7 million hectares of land have been cultivated with the transgenic crop that was increased up to 170 million hectares till 2012 and still it is increasing. Continuous efforts are made to bring the rice yield maximum for developing the large market of it globally [2]. Therefore, it is necessary to develop more cultivars of rice by using

either old plant breeding techniques or new targeted genome editing techniques like zinc finger proteins (ZFNs), transcription activator-like nucleases (TALENs) and clustered regularly interspaced short palindromic repeats associated with Cas9 protein (CRISPR-Cas9) to develop cultivar of rice for improved agronomical traits.
