Essay On Rice Cultivation

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Rice is inevitably an important staple food crop supporting half of the world population. Rice cultivation has gained importance worldwide not only as a source of dietary constituents, but also play a major role in socio economic development, providing food security, poverty alleviation, employment, sustainable development and maintenance of cultural heritage etc., (Nguyen and Ferrero, 2006). It is also a favorable model crop plant among cereals for genetic improvement studies and functional genomics due to its small genome size and availability of full genome sequence. The main concern over rice cultivation is the increasing demand over supply while there is remarkable depletion in cultivable land area. Many challenges lie ahead of cultivars to achieve the required target/need in coming years and rice diseases are among one of the major challenges.

Rice plants are frequently under attack from various insects, pest and pathogens. Most of the elite rice cultivars and varieties with favorable taste and yield such as Basmati, Sambha Mashuri, Swarna, other aromatic rice etc. are very much prone to diseases. Bacterial blight (BB) is one of the major diseases of rice affecting as much as 20-50% yield loss in severe cases (Reddy 1989; Mew 1993; Adhikari et al. 1994). Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial leaf blight disease in rice. It is a vascular disease resulting in systemic infection. To control the disease, use of chemical pesticides, biological control agents and host mediated resistance have been widely adopted. However, spraying pesticides have tremendous long term ill effects to environment and consumers. In order to provide durable, economical and sustainable disease resistance to plants, host ...

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... from different Asian countries (Gu et al. 2004). This gene was first identified in Oryza minuta and mapped on chromosome 6 of rice. xa5 confer race specific resistance against Phillipines Xoo race 1 (PXO86). The xa5 gene is a mutant form of rice transcription factor OsTFIIAγ5 (Xa5) where there was a substitution variant of single amino acid V39E (Iyer et al. 2004).

Our analysis which was conducted in wild species and domesticated rice may help in understanding the natural selection and evolution of the important BB resistance genes to sustain under ever evolving pathogen constraint. Studying the pattern and structure of genetic variation of BB R genes will help us in understanding the evolutionary history of these genes. It will also help in identifying good resistance source which may be further utilized for developing disease resistance varieties.
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