Bacterial blight (BB) is a serious disease of rice in India. We have used molecular marker-assisted selection in a backcross breeding program to introgress three genes (Xa21, xa13, and xa5) for BB resistance into Triguna, a mid-early duration, high yielding rice variety that is susceptible to BB. At each generation in the backcross program, molecular markers were used to select plants possessing these resistance genes and to select plants that have maximum contribution from the Triguna genome. A selected BC3F1 plant was selfed to generate homozygous BC(3)F(2) plants with different combinations of BB resistance genes. Plants containing the two-gene combination, Xa21 and xa13, were found to exhibit excellent resistance against BB. Single plant selections for superior agronomic characteristics were performed on the progeny of these plants, from BC(3)F(3) generation onwards. The selected plants were subjected to yield trials at the BC(3)F(8) generation and were found to have a significant yield advantage over Triguna. The newly developed lines are being entered into national multi-location field trials. This work represents a successful example of the application of molecular marker-assisted selection for BB resistance breeding in rice.

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The contribution of rice breeding for ensuring food security in India is well known. Organized rice breeding is nearly eight decades old in the country which started with the establishment of Central Rice Research Institute at Cuttack in the year 1946. Thereafter, the rice breeding programmes have undergone several transformations to meet the needs of stakeholders at both regional and national level. For all the rice ecologies of the country, high yielding varieties were developed by deployment of the required genes. Initially the objectives were met only through phenotypic selections based on breeders' own skills. With time, the rice breeders of the country adopted the advances in the fields of science and technologies especially in the areas of plant sciences. From the initial phase of users of methodologies and materials developed elsewhere, the rice scientists of India have transformed themselves to discover useful genes from the vast germplasm resources of the country and utilize them as per the local requirements through marker assisted selection. Despite the progress made in last few decades, the genetic gain from breeding programmes is becoming stagnant over time and the increased yield in current years are now attributed more to production interventions. The rice breeders of India need to take advantage of the recent developments of speed breeding, whole genome sequences of various Oryza species, advanced phenomics and computational methods, high throughput genotyping platforms, tissue culture and genome editing tools etc. to shift from its current approach of "breeding by chance" to "breeding by design" and to bring significant improvements in the rate of genetic gain per generation.

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From a ship-to-mouth existence at the time of its Independence, India became a food sufficient country due to the research and policy interventions during the green revolution era and in the last six decades. The country witnessed a phenomenal increase in the production and productivity of rice and wheat and presently the country is exporting significant quantities of rice. However, there are multiple challenges in ensuring food and nutritional security through rice in the coming decades including a rapidly changing climate and a plateauing of rice yields has been witnessed in the last two decades in many rice growing countries across the world including India. It is therefore imperative to enhance rice productivity and production through application of modern tools of science. This review traces the developments related to rice research and yield improvement over the last six decades and discusses about the conventional and modern approaches to enhance grain yield in rice. These approaches include pre-breeding, wide-hybridization, new plant type/ideotype breeding, heterosis breeding, marker and genomics-assisted breeding, haplotype-based breeding, transgenic breeding and genome editing.