37. A new source of cytoplasmic male sterility found in Bangladesh Boro rice

    Tsukasa Nagamine1, Koh-ichi Kadowaki1, Akio GoTo2 and Takeshi Ajioka2
    1) National Institute of Agrobiological Resources, Kannondai 2-1-2, Tsukuba-shi, 305 Japan
    2) Association for International Cooperation of Agriculture and Forestry, Chiyoda-ku, Tokyo, 102 Japan

     The male-sterile cytoplasm (cms-bo) derived from Chinsurah Boro II is widely utilized for breeding hybrid varieties of Japonica rice. In order to avoid genetic vulnerability due to the single origin of male-sterile cytoplasm, other sources of cytoplasms are desired.
    Four boro varieties, i.e., Tupaboro (Habiganji boro II), Khiaboro (Habiganji boro IV), Poshusail (Habiganji boro VI), and Habiganji boro VIII, introduced from Bangladesh in 1983, were crossed with a Japonica variety Akihikari in reciprocal directions and were backcrossed repeatedly, using Akihikari as recurrent parent. Khiaboro cytoplasm with nuclear genome of Akihikari showed male sterility and a cytoplasmic male-sterile line was established after eight successive backcrosses.
    Its test crosses for pollen-fertility restoration exhibited that the cytoplasm of this line was different from [cms-bo]. Some of Japanese upland varieties and many of Indica varieties restored fertility (Table 1).

Table 1. Seed-fertility restoration patterns for the MS cytoplasm from

Khiaboro (based on number of varieties)
 

Cross parent: 

Varietal group

 No resto.

(0-15%)

 Weak 

(16-25%)

 Partial 

(26-40%)

 Strong (>41%) Total
Indica 15 11 12 16 54
Japonica Paddy 45 0 1 1 47
Upland 2 0 4 0 6

    Southern hybridization analysis of mitochondrial DNAs (mtDNAs) isolated from seedling of this line was conducted with eight kinds of probes, i.e., atp6, atpA., cob, coxl, cox II, rps12, rp12/rpsl9, and rp15/rps14. It was found that the atp6 in Khiaboro had one band, while that in Chinsurah Boro II had two bands. The analysis with other seven probes showed the same pattern between the two cytoplasms, [cms-bo] and [cms-Khiaboro]. This suggests that the structure of mtDNAs of Khiaboro and that of Chinsurah Boro II differ from each other at the region around the atp6 only.