2012, pp 261-298
Date: 18 Jun 2012

Genomics of Hevea Rubber

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Abstract

Hevea brasiliensis is the most recent domesticated tree species from Amazonian rain forest producing latex of commercial utility. Major hurdles for genetic improvement of rubber tree were attributed to its perennial nature, long juvenile period, and a narrow genetic base. Further, the limited availability of Hevea genomic resources/information is another impediment to genomics-assisted crop improvement. Improvement of rubber tree in terms of latex production through breeding was the major focus of the scientific community dealing with the crop. Due to unidirectional selection for yield, other secondary attributes of rubber plants were lost during the process of developing high-yielding clones. Work on plant genomics gained momentum only after whole genome sequencing of Arabidopsis thaliana in 2000 (Arabidopsis Genome Initiative, 2000) followed by rice (International Rice Genome Sequencing Project, 2002) and poplar, the first tree genome (International Populus Genome Consortium, 2004). However, rubber genomics is still in its infancy. Initial molecular work started in the 1990s with cloning and characterization of latex biosynthesis genes followed by the studies on gene expression influenced by various biotic and abiotic stresses, tapping panel dryness (TPD), and ethylene stimulation of latex production. Simultaneously, different genetic markers were established in rubber for understanding the inheritance and diversity of natural variation existing among the Wickham and wild populations. Genetic markers were used successfully to generate linkage map for QTLs involving disease tolerance. During the last decade, transgenic research also progressed significantly with the development of transgenic Hevea clones with overexpressed MnSOD gene effective against TPD and drought stress. In recent years, with the advent of new-generation sequencing techniques, large-scale EST generation in rubber had been possible, which provided insights into genomic architecture and helped to elucidate genes involved in biological processes like latex production. In the absence of whole genome sequence information, the available transcriptome sequences form a potential resource to be utilized in genetic enhancement of rubber tree. The future challenge is to translate and integrate available genomic knowledge into appropriate methodologies, which we believe will revolutionize future Hevea breeding program.