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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with 2 mg/l 2,4-D, 0.2 mg/l 4PU (a growth stimulating substance recently found by our chemistry department, details unpublished), 0.05 mg/l NAA, and 0.1 mg/l KT (kinetin).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
plants
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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)
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Plant height(cm) 80 80 77 80 130 150
Spikelets
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
(January)
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
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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.
