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International Rice Research Institute, P.O. Box 933, Manila, Philippines
The genus Oryza to which cultivated rice (Oryza sativa L.) belongs has more than 20 wild species. These wild species are an important reservoir of useful genes for resistance to major diseases and insect pests and tolerance to abiotic stresses. To widen the rice gene pool and for transfer of useful alien genes, we have produced hybrids of rice varieties with eight wild species (Table 1). In these cross-combinations, 15977 rice florets were pollinated with pollen of eight species and 1420 seeds were obtained. The seed set ranged from 3.8 to 22.1 percent average being 8.9 percent. From crosses of rice with 12 accessions of wild species, 204 hybrid plants were produced through embryo rescue. These hybrids were produced specifically to transfer genes for tungro tolerance from O. officinalis (105220) and O. latifolia (105141, 105142); yellow stemborer and tungro tolerance from O. ridleyi (100821); brown planthopper and bacterial leaf blight resistance from O. rhizomatis and O. eichingeri; high biomass from O. alta and to determine genomic constitution of O. ridleyi, O. granulata and O. indandamanica.
Immature embryos, 10-14 day of post pollination were excised from different cross-combinations. These embryos were cultured on 1/4 MS medium and were incubated in the dark (25+-1 deg C) until germination following the procedure of Jena and Khush (1984). The seedlings were kept in the light incubated room up to three leaf stage and transferred to soil after growing in liquid culture medium for 10 days. The hybrid nature of some of these plants was confirmed from PMC analysis. In general, the hybrids were intermediate in morphological characters between the two parents (Fig. 1). The F1 hybrids were male sterile. These hybrids are being maintained and multiplied through tiller propagation. We have
Table 1. Interspecific hybrids produced through embryo rescue between
cultivated rice (O. sativa) and eight wild species of Oryza
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Hybrid-combination
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Wild species (male)
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O.sativa Species Genome Accession Florets Seed set Embryos Hybrid
(female) pollinated (No.) cultured plants
(No.) (No.) (No.)
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IR42 O. eichingeri CC 105181 48 20 18 13
IR64(4n) " " 105181 12 6 1 1
IR31917-45-3-2 " " 101422 184 33 5 1
IR54 " " 101422 112 12 0 0
IR64 " " 101422 106 12 4 1
IR64(4n) " " 101430 55 5 4 4
IR20 O. officinalis CC 105220 90 30 6 1
IR22 " " 105220 238 2 0 0
IR24 " " 105220 416 6 0 0
IR31917-45-3-2 " " 105220 452 10 1 0
IR70 " " 100878 105 1 1 1
IR31917-45-3-2 O.rhizomatis CC 105432 127 26 19 8
IR36(4n) " " 105432 609 2 0 0
IR20 O. latifolia CCDD 105141 441 64 39 25
IR22 " " 105141 786 185 44 33
IR24 " " 105141 1264 173 79 36
IR31917-45-3-2 " " 105141 1745 131 49 6
IR64(4n) " " 105141 122 2 0 0
IR20 " " 105142 384 32 8 6
IR22 " " 105142 294 27 5 2
IR24 " " 105142 932 40 19 15
IR31917-45-3-2 " " 105142 407 37 17 13
IR36(4n) " " 105142 103 11 8 0
IR31917-45-3-2 O.alta CCDD 101395 111 63 0 0
IR64 " " 101395 54 18 3 2
IR64(4n) " " 101395 80 0 0 0
IR36(4n) " " 101395 121 0 0 0
IR72 O. ridleyi unknown 100821 1263 3 1 1
IR74 " " 100821 2091 224 40 27
IR31917-45-3-2 " " 100821 1259 128 12 1
IR56 O. granulata unknown 100879 372 42 2 0
IR31917-45-3-2 " " 100879 537 45 14 3
IR36(4n) " " 100879 642 3 0 0
IR31917-45-3-2 O.indandamanica unknown - 160 1 0 0
IR36(4n) " " 95 0 0 0
IR64(4n) " " 160 26 4 4
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already produced BC1 plants through embryo rescue from crosses of IR42 X O. eichingeri, IR31917-45-3-2 X O. rhizomatis and IR31917-45-3-2 X O. granulata. We now have interspecific hybrids involving elite breeding line/varieties of rice with 12 wild species having genomes other than A.
Reference
Jena, K. K. and G. S. Khush, 1984. Embryo rescue of interspecific hybrids and its scope in rice improvement. RGN 1: 133-134.
