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Contibuted by Dr. Mohamad bin Osman
Universiti Kebangsaan Malaysia

Introduction

Grain elongation on cooking and aroma are two major characteristics of high quality rices. Elongation of the grain after cooking without appreciable increase in width is a desired property for some fine-grained and aromatic rice such as Basmati from India and Pakistan. Grain elongation, like aroma, is a major component of the grain quality characteristics of Basmati types. This type of rice is an important commercial commodity for the economies like India, Pakistan and Thailand. In Malaysia, there is an increasing demand for quality rice in domestic markets.

Quality Rice

Due to such demands, MARDI had initiated a special breeding programme to breed for high quality rices, alongside of the mainstream breeding programme. As a result, the special programme had successfully released two new high quality varieties, namely MRQ 50 (aka Puteri) and MRQ 74 (aka Mas Wangi). Two special quality traits present in these varieties, but not present in previously released varieties, are grain elongation and aroma of cooked rice.

Grain elongation characteristic is derived from is a mutant line named “Mahsuri Mutant”, a product of the collaborative research initiated by UKM and MARDI in 1979 to use induced mutations in rice breeding. Mahsuri Mutant possesses the grain elongation characteristic very much akin to that found in Basmati, and is found to be controlled by one or two major genes. This is the only known local source of grain elongation characteristic. Consequently, breeders have targeted the grain elongation of Mahsuri Mutant as one of the invaluable quality traits. Since then, efforts have been stepped up to transfer this special trait into elite breeding lines through conventional methods. The internal anatomical structure of grain, cell shape and arrangement might have influence on the water uptake and the nature of swelling on cooking. Preliminary studies indicated that, the internal cracks for Mahsuri Mutant was substantially increased when it was artificially aged.

Results and Discussion

Seven sets of primer for grain elongation were used and tested in PCR amplification analyses. The results obtained showed that six sets out of seven selected and synthesised primers were functional. However, the expected fragment size between grain elongation and non-grain elongation could not be discriminated by agarose gel electrophoresis. Therefore, the amplicons were sequenced.

The sequenced regions of chromosome(s) were analysed using BLAST programme to identify their identity so that these could be used to generate new and better molecular markers that would tag closer to the gene of interest, i. e. the grain elongation gene in our rices.

In the sequence analyses, it was found that 93% (Mahsuri Mutant) were identical to Oryza sativa microsatellite MRG4671 containing (AAT)X12, closest to marker C1338 Oryza sativa chromosome 10 sequence (GenBank Accession No: AY022346; nt. 50-196), whereas 96% (Basmati 370) and 96% (MRQ 50) were both identical to certain region of Oryza sativa chromosome 10 BAC OSJNBa0015J15 genomic sequence (GenBank Accession No: AC026758; nt. 87205-87229) which is referred to Oryza longistaminata receptor-like kinase protein (Xa21). From the genetic map of rice chromosomes, grain elongation marker is close to rice blast disease marker (Xa21). Based on the present results, only Mahsuri Mutant’s nucleotide sequence would be used in adopting genome walking method to generate novel molecular markers. Subsequently, these new markers would be tested for their utility for marker-assisted selection in our rice breeding programme

Authors:
Mohamad, O.(1), Hadzim, K.(3), Azlan, S.(3), Abdullah, M. Z.(4), Zainah, M.(2), Salwa, A. S.(1), Nur Samahah, M. Z.(1) & Amiran, N.(1)
1 Universiti Kebangsaan Malaysia, Bangi
2 Malaysian Agricultural Research & Development Institute (MARDI)
3 Formerly with Malaysian Agricultural Research & Development Institute (MARDI)
4 Universiti Malaysia Terengganu, Kuala Terengganu

Source: Poster exhibition at Malaysia Technology Expo (MTE 2008) held at Putra World Trade Centre (PWTC), Kuala Lumpur on 21-23 February 2008.

For the complete paper please contact the main author: mbopar@pkrisc.cc.ukm.my
Website: www.ukm.my

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