**Abstract**

Rice is the predominant crop in India and is the staple food in eastern and southern Indian populations. One of the oldest grown crops is rice. The initial discovery of cytoplasmic male sterile (CMS) three-line system made it possible to produce hybrids that significantly increase rice yields compared to its inbred counterparts. Further genetic and molecular studies help elucidate the mechanisms involved in CMS male sterility. Additional CMS types were also discovered with similar genetic control from wild sources by interspecific hybridization. In India more than 1200 varieties were released for cultivation suitable different ecosystems and out of them 128 varieties have been contributed from NRRI, Cuttack. A list of these varieties are furnished below with their duration, grain type, yield potential, reaction to major disease and insects grain quality and tolerance to different adverse situations. Recent advances in molecular approaches used in modern rice breeding include molecular marker technology and marker-assisted selection (MAS); molecular mapping of genes and QTLs and production of hybrids and alien introgression lines (AILs). Genomic selection (GS) has been projected as alternative to conventional MAS. GS has huge potential to enhance breeding efficiency by increasing gain per selection per unit time. Due to the adaptation of semi dwarf high yielding varieties, combined with intensive input management practices, the country witnessed an impressive rice production growth in the post-independent period. Rice production was increased four times, productivity three times while the area increase was only one and half times during this period. The projected rice requirement by 2025, in order to keep up with increasing population, is about 130 m.t. The challenge of growing rice production is made more difficult by declining trends in HYV's yields, decreasing and degrading natural resources such as land and water and a severe labour shortage.

**Keywords:** Rice, Hybrid, Heterosis, Marker Assisted Selection, Genomic Selection

#### **1. Introduction**

Rice (*Oryza sativa* L.) is one of the most important staple foods that feed more than half of the world's population; Asia and Africa are the major consuming regions [1]. For at least half of the world's population, rice is the most significant source of calories. As a result, many countries have developed strategies to achieve rice self-sufficiency by growing the area under cultivation or increasing yield per

unit area. In case of rice, however, grain quality is just as critical as yield. Heterosis is the ability of F1 offspring to outperform either parent and it is the only way to achieve full hybrid vigor in crop plants. For decades, this has been a factor in the production of superior cultivars for many crops in agriculture and enthusiastic geneticists [2]. In a hybrid compared to HYVs, the appropriate combination and manipulation have produced benefits [3]. Since the discovery and growth of the cytoplasmic male sterile (CMS) source in the middle of the twentieth century, heterosis was possible due to its self-pollinating existence (0.3–3.0% outcrossing). Nanyou 2, the first indica rice hybrid, was released for cultivation in China in 1974.

Subsequently, relatively heterotical hybrid rice (HR) breeding approaches were adopted, such as two-line system and super hybrids, which complemented Chinese food security and liveling standards significantly in India. In 1989, the Indian Council of Agricultural Research (ICAR) launched a special goal-oriented and time-bound project for rice called "Promotion of Research and Development Efforts on Hybrids in Selected Crops," which included 12 network centres. Around four years of intensive research (1989–1993) paid off handsomely, and India became the second country after China to grow and commercialize hybrid rice. APRRI, Maruteru, launched the first hybrid variety APRH-1 in 1993–1994 for Andhra Pradesh. So far, 117 rice hybrids (36 from public organization and 81 from private sector) have been produced, with duration ranging from 115 to 150 days and a total area of 3.0 mha, accounting for 7.0 percent of India's total rice acreage [4]. As a result, breeding for consumer-favored grain qualities has become a major target for breeding programs all over the world. Grain quality must be clearly identified and the genes underlying their regulation deciphered before it is possible to breeder for fastidious customer preference. Rice is a staple food crop that accounts for more than a fifth of all calories consumed by humans [5]. Since rice is the most common cereal crop in most Asian countries and is the staple food for more than half of the world's population, even a small increase in rice grain micronutrient content could have a major effect on human health. Hybrid rice is the product of a cross between two rice parents with genetically different traits. When the right parents are chosen, the hybrid can outperform both parents in terms of vigor and yield. Higher yields, increased vigor, and increased resistance to diseases and insect resistance are all advantages of hybrid rice [6].

### **2. Hybrid rice breeding program in India**

Rice is the predominant crop in India and is the staple food in eastern and southern Indian populations. One of the oldest grown crops is rice. The two cultivated species of rice are (i) *Oryza sativa* - Asian rice Cultivated Species of Rice (A) Asian Rice (*Oryza sativa* L.). It is predominant species which has spread to different part of world. (B) African Rice (*Oryza glaberrima* L.) [7]. It's also only found in Africa's tropical region. Based on morphological and physiological characteristics as well as geographical adaptation, Asian rice is divided into three ecological forms. **1.** *Indica*: Grown in tropical climate such as India, Sri- Lanka, China, Thailand, Malaysia, Taiwan *2. Japonica*: Japan and Korea have a temperate climate *3. Javanica:* Indonesian hybrid of Indica and Japonica (**Table 1**).

#### **3. IRRI's hybrid rice program**

Germplasm, parents and hybrids are being developed through new breeding and seed technology by researcher. Currently scientists are working for the hybrids rice production with the Collaboration of NARS and private sectors.


**Table 1.** *Brief history of hybrid rice.*
