Identification of the low-tillering gene in rice (Oryza sativa L.)



   The genetic mechanism and allelic relationship between the low-tillering in two Japonica-type rice varieties Aikawa 1 and Shuho were clarified, and the chromosomal location was also identified with molecular (DNA) markers, to apply for the breeding program targeting to develop the new plant typerice as ones of gene sauces.


   The genetic mechanisms of low-tillering in two Japonica-type rice, Aikawa 1 and Shuho, were clarified and the controlling gene was identified on rice chromosomes using molecular markers. In these two Japonica varieties, the single dominant gene controlling low-tillering was confirmed on the basis of segregation analyses in each BC1F2 population derived from the crosses with Indica-type varieties IR64 and IR72 as recurrent parents, respectively.
   Aikawa 1 and Shuho were found to have the same low-tiller gene based on results of allelism tests in F2 populations derived from reciprocal crosses between Aikawa 1 and Shuho. Transgressive segregation was not observed in any of the distributions of 378 Aikawa 1/Shuho and 425 Shuho/Aikawa 1 F2 plants.
   The low-tiller gene was mapped between the SSR marker, RM149, and the RFLP marker, XNpb56, on the long arm of chromosome 8 using DNA markers (Fig. 1). As no gene related to low-tillering has been reported yet in this region, the genes found in Aikawa1 and Shuho plants were tentatively designated as Ltn (t).
   The near isogenic line (NIL) that introduced Ltn (t) into the elite Indica-type varieties IR64 and IR72 were developed from the advanced recurrent backcrosses of progenies to clarify yield ability of low-tiller plant types and to incorporate more detailed genetic and physiological analyses (Fig. 2). Partial sterility and malformed palea in the panicles of NILs were observed; this may have occurred due to the multiple effects of Ltn (t).
   Information on genetic mechanisms and mapping of low-tiller genes will be used for breeding programs using marker-aided selection or map-based cloning of Ltn (t); NILs will also be useful as breeding materials for Indica-type varieties.

Figure, table


    Table 1.
    Fig. 1. Identification of Ltn (t) locus using DNA markers.
    A: BC1F2 (IR64/Aikawa1//IR64) family lines (n=33).
    B: BC1F2 (IR72/Shuho//IR72) family lines (n=74).

    Fig. 2.
    Fig. 2. Near isogenic lines introduced with the low-tiller gene, Ltn (t), into the IR64 and IR72 genetic backgrounds.
    A, IR64; B, IR64 NIL (IR64/Aikawa1/5/ IR64,BC6F3); C, Aikawa 1; D, IR72; E, IR72 NIL (IR72/Shuho/5/IR72, BC6F3); F, Shuho.

Japan International Research Center for Agricultural Sciences Biological Resources Division


Technical A

Term of research

FY2003 (FY1999-2004)

Responsible researcher

FUKUTA Yoshimichi ( International Rice Research Institute )

ARAKI Etsuko ( National Agricultural Research Center for Western Region )

KATO Hiroshi ( Miyazaki Prefectural Agricultural Research Institute )

TSUNEMATSU Hiroshi ( Biological Resources Division )

Ebron Leodegario A. ( International Rice Research Institute )

SHEEHY Jhon E. ( International Rice Research Institute )

KHUSH Gurdev G. ( International Rice Research Institute )

Publication, etc.

Araki, A., Ebron, L.A., Cuevas, R.P., Mercado-Escueta, D., Khush, G.S., Sheehy, J.E., Kato, H. and Fukuta, Y. (2003a): Identification of low tiller gene in rice cultivar Aikawa 1. Breed. Res., 5, Suppl. 1, 95.

Araki, E., Ebron, L.A., Cuevas, R.P., Mercado-Escueta, D., Khush, G.S., Sheehy, J.E., Kato, H. and Fukuta, Y. (2003b): Genetic analysis of low tillering in Japonica-type rice (Oryza sativa L.) cultivar Aikawa 1. Philippine journal of Crop Science, 28 (1), 40.

Fukuta, Y., Araki, E., Ebron, L.A., Cuevas, P.R., Mercado-Escueta, D., Khush, G.S., Sheehy, J., Tsunematsu, H. and Kato, H. (2004): Identification of low tiller gene in rice two varieties, Aikawa 1 and Shuho in rice (Oryza sativa L.). Plant & Animal genome XII, Abstract, 167.

Araki, E., Fukuta, Y., Ebron, L.A., Cuevas, P.R., Mercado-Escueta, D., Khush, G.S., Sheehy, J.E., Tsunematsu, H. and Kato, H. (2004): Fine-mapping of a low tillering gene in a Japonica-type rice (Oryza sativa L.), Aikawa 1. World Rice Research Conference abstract, 138.

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