9. Character expression of CC and CCDD genomes in hybrids with diploid and tetraploid strains of O. sativa

Z. X. LI1, D. X. LIU1, Wen-Jin YU1 and Y. SONG2

1) Chengdu Institute of Biology, Academia Sinica, Chengdu 610015, China

2) Sichuan Academy of Agricultural Sciences, Chengdu 610016, China

A male-sterile line (765-5-230) and an autotetraploid line (P187) of O. sativa were crossed with lines of O. grandiglumis (genome CCDD) and O. officinalis (CC), respectively, using O. sativa lines as the maternal parents. The hot-water emasculation method (45 deg C, 5 min) was used. The F1 embryos were excised 10-13 days after pollination, sterilized in 70% alcohol and 0.1% mercuric chloride (8- 15 min), and were rinsed iii sterile water several times. Then, the embryos were incubated on modified M6 basal medium supplemented with 2 mg/l 2,4-D, 0.2 mg/l 4PU (a growth stimulating substance recently found by our chemistry department, details unpublished), 0.05 mg/l NAA, and 0.1 mg/l KT (kinetin). The cultures were kept in dark at 25+/-3 deg C for callus induction. Calli formed from embryos were cut into pieces (5 min) and transferred to N6 basal medium with 2 mg/l KT, 0.2 mg/l 4PU, and 0.5 mg/l NAA for regeneration of plants. The

Table 1.  Morphological and physiological characters of parental lines and F1
                 P187   P187X      O.officinalis 765-5-230 765-5-230X O.grandi-
Character      (AAAA) O.officinalis  (CC)          (AA)    O. grandi-  glumis
                        (F1)                               glumis (F1) (CCDD)
Plant height(cm)  80     80           77            80         130       150
 per panicle     100     85           50           150         140       207
% spikelet
  fertility       30      0           50             0           0        70
Panicle exertion  good partly       good           good        good      good
Color of leaf
 margin and
 stem base       green  green       green          purple      purple    green
Leaf pubescence  pubes. pubes.      pubes.         pubes.      medium    smooth
Green leaves at
 maturity          3     >4            3             3           5         5

                  no    wither      tolerate        no      flowering flowering
Cold resistance resist. ca.5 deg C  to 8-1O deg C resist.   below 15 C  at 5 C

Blast resistance   M      R            R             M          R          R

Stem borer
 resist.           M      R            R             M          R          R

Brown plant-
 hopper resist.    M      R            R             M          R          R

Drought           no     wither     tolerate                tolerate   tolerate
 resistance    resist.   at soil    to soil         no      to soil    to soil
                         cracking   cracking      resist.   cracking   cracking
R-resistant, M-medium resistance.
cultures were kept at 25+/-3 deg C under 12 h/day illumination (2000 Lux) to induce green plantlets. From plantlets with 3 to 5 leaves, the tips of primary and secondary roots were taken and chromosomes were observed using the wall degradation hypotonic (low osmotic pressure) and flame-drying method.

Most of the plants obtained from both crosses by the embryo rescue technique were triploids (2n = 36). A few aneuploids having 2n+1, 2n+2 and 2n+3 chromosomes were also obtained. Some other cells showed 42 chromosomes.

Characters of the parents and F1 hybrids observed are given in Table 1. The F1 plants showed useful characters such as resistance to cold, drought and different diseases and pests. All the F1 plants were male-sterile and produced no seeds. The F1 plants from both crosses were pollinated with the pollen of O. sativa cultivars. One plant from 765-5-23O X O.grandiglumis produced a few shrunken seeds. The F1 plants are maintained vegetatively for further backcrosses.