DEVELOPMENT OF MONOSOMIC ALIEN ADDITION LINES AND INTROGRESSION OF GENES FROM ORYZA-AUSTRALIENSIS DOMIN TO CULTIVATED RICE ORYZA-SATIVA L

Oryza australiensis, a diploid wild relative of cultivated rice, is an important source of resistance to brown planthopper (BPH) and bacteri al blight (BB). Interspecific hybrids between three breeding lines of O. sativa (2n = 24, AA) and four accessions of O. australiensis (2n = 24, EE) were obtained through embryo rescue. The crossability ranged f rom 0.25% to 0.90%. The mean frequency of bivalents at diakinesis/meta phase I in F-1 hybrids (AE) was 2.29 to 4.85 with a range of 0-8 bival ents. F-1 hybrids were completely male sterile. We did not obtain any BC, progenies even after pollinating 20,234 spikelets of AE hybrids wi th O. sativa pollen. We crossed the artificially induced autotetraploi d of an elite breeding line (IR31917-45-3-2) with O. australiensis (Ac e. 100882) and, following embryo rescue, produced six F, hybrid plants (AAE). These triploid hybrids were backcrossed to O. sativa. The chro mosome number of 16 BC1 plants varied from 28 to 31, and all were male sterile. BC2 plants had 24-28 chromosomes. Eight monosomic alien addi tion lines (MAALs) having a 2n chromosome complement of O. sativa and one chromosome of O. australiensis were selected from the BC, F, proge nies. The MAALs resembled the primary trisomics of O. sativa in morpho logy, and on the basis of this morphological similarity the MAALs were designated as MAAL-1,-4,-5,-7,-9,-10,-11, and -12. The identity of th e alien chromosome was verified at the pachytene stage of meiosis. The alien chromosomes paired with the homoeologous pairs to form trivalen ts at a frequency of 13.2% to 24.0% at diakinesis and 7.5% to 18.5% at metaphase I. The female transmission rates of alien chromosomes varie d from 4.2% to 37.2%, whereas three of the eight MAALs transmitted the alien chromosome through the male gametes. BC, progenies consisting o f disomic and aneuploid plants were examined for the presence of O. au straliensis traits. Alien introgression was detected for morphological traits, such as long awns, earliness, and Amp-3 and Est-2 allozymes. Of the 600 BC2 F-4 progenies 4 were resistant to BPH and 1 to race 6 o f BB. F-3 segregation data suggest that earliness is a recessive trait and that BPH resistance is monogenic recessive in two of the four lin es but controlled by a dominant gene in the other two lines.