Oryza minuta J. S. Presl ex C. B. Presl is a tetraploid wild rice with resistance to several insects and diseases, including blast (caused by Pyricularia grisea) and bacterial blight (caused by Xanthomonas oryzae pv. oryzae). To transfer resistance from the wild species into the genome of cultivated rice (Oryza sativa L.), backcross progeny (BC1, BC2, and BC3) were produced from interspecific hybrids of O. sativa cv 'IR31917-45-3-2' (2n=24, AA genome) and O. minuta Acc. 101141 (2n=48, BBCC genomes) by backcrossing to the O. sativa parent followed by embryo rescue. The chromosome numbers ranged from 44 to 47 in the BC1 progeny and from 24 to 37 in the BC2 progeny. All F1 hybrids were resistant to both blast and bacterial blight. One BC1 plant was moderately susceptible to blast while the rest were resistant. Thirteen of the 16 BC2 progeny tested were resistant to blast; 1 blast-resistant BC2, plant 75-1, had 24 chromosomes. A 3 resistant: 1 susceptible segregation ratio, consistent with the action of a major, dominant gene, was observed in the BC2F2 and BC2F3 generations. Five of the BC1 plants tested were resistant to bacterial blight. Ten of the 21 BC2 progeny tested were resistant to Philippine races 2, 3, and 6 of the bacterial blight pathogen. One resistant BC2, plant 78-1, had 24 chromosomes. The segregation of reactions of the BC2F2, BC2F3, and BC2F4 progenies of plant 78-1 suggested that the same or closely linked gene(s) conferred resistance to races 2, 3, 5, and 6 of the bacterial blight pathogen from the Philippines.
Intrachromosomal mapping studies were used to locate the positions of the genes Kr1 and Kr2, which control the crossability of wheat with Hordeum bulbosum, on chromosomes 5B and 5A, respectively. The location of Kr1 was established using the telocentric mapping technique and found to be on the long arm of chromosome 5B, distal to the centromere with a mean recombination frequency of 44.8±3.28%. Kr2 was located on the long arm of chromosome 5A by linkage with the major gene markers Vrn1, controlling vernalization requirement, and q, controlling ear morphology. Kr2 is closely linked to Vrn1, with a mean recombination frequency of 4.8±4.66%, and is distal to q with a mean recombination frequency of 38.1±10.60%. The similar locations of Kr1 and Kr2 on homoeologous chromosomes suggest that these two loci are homoeoallelic. Significant correlations between Hordeum bulbosum and rye crossability confirmed that Kr1 and Kr2 control the crossability of wheat with both species.
Triticurnaestivum, wheat, Hordeum bulbosum, pollen grain germination, pollen tube growth, frequency of fertilization, gibberellic acid, temperature.A quantitative examination of pollen grain germination and pollen tube growth within the ovary wall was made in selected wheat x tetraploid H. bulbosum hybridizations, to investigate the effect of the wheat and the H. bulbosum genotype on these characters. As expected, variation at the known crossability loci had no effect on pollen grain germination. The frequency of pollen tube penetration of the ovary wall was, however, severely reduced when the dominant alleles were present. Pollen tube penetration was nevertheless observed in 3 of the 110 ovaries examined of the non-crossable cultivar Highbury. The H. bulbosum genotype had a much smaller effect on these characters, but significant differences between the clones were observed in the numbers of pollen tubes initially penetrating the ovary wall. Although two H. bulbosum genotypes showed no significant differences in the number of ovaries with pollen tubes at the base of the ovule, significant differences in the frequency of fertilization were observed. The possible cause of this discrepancy is discussed.The frequency of fertilization in crossable wheat x H. bulbosum hybridizations was improved by the application of gibberellic acid within 10 minutes of pollination, and reduced by an increase in the ambient temperature from 20°C to 26°C. Fertilization following the pollination of non-crossable wheat genotypes was not affected by either of these factors.
S. 1987. Production and cytogenetic analysis of hybrids between Triticum aestivum and some caespitose Agropyron species. Genome, 29: 537-553. Intergeneric hybrids between Triticum aestivum L. cultivars and 12 traditional Agropyron species were produced in variable frequencies, lowest being 0.35% for A. stipaefolium to a high of 41.98% for A. varnense. The crossing success of T. aestivum cultivars ranged from 'Chinese Spring' > 'Pavon-76' = 'Nacozari-75' > 'Fielder' = 'Fremont' > 'Glennson-81'. All FI hybrids were somatically stable. The new combinations were with A. curvifolium (Thinopyrum curvifolium), A. rechingeri (T. sartorii = rechingeri) , A. scythicum (T. scythicum), and A. stipaefolium (Pseudoroegeneria stipaefolia). All hybrids were perennial and possessed a modified phenotype that was intermediate between the parents involved in the hybrid combinations with major variation in spike morphology (elongated spikes with lax internodes). High-pairing hybrids, presumably owing to suppression of the Ph locus were of T. aestivum -A. scythicum (15.3 1 I + 2.25 I1 rings + 6.92 I1 rods + 0.32 111) and T. aestivum -A. stipaefolium (10.6 I + 7.08 I1 rings + 4.41 I1 rods + 0.54 111). In the other combinations, the pairing was either low or high, and if high, pairing was attributed to autosyndetic association of the alien genome chromosomes. Based on the meiotic pairing data, alien species that were segmental allotetraploids or partial autopolyploids, or segmental allohexaploids or autoallohexaploids, may be advantageous in developing backcross derivatives with synthetic genomes. Production of fertile amphiploids was restricted to T. aestivum -A. rechingeri. ., et FAROOQ, S. 1987. Production and cytogenetic analysis of hybrids between Triticum aestivum and some caespitose Agropyron species. Genome, 29 : 537-553. Des hybrides intergknkriques entre des cultivars de Triticum aestivum L. et 12 especes communes d'Agropyron ont kt6 produits en frkquences variables, depuis les plus basses avec 0,35% pour A. stipaefolium vers les plus hautes avec 41,98% pour A. varnense. Le succes des croisements des cultivars de T. aestivum a Cvoluk comme suit: 'Chinese Spring' > 'Pavon 76' = 'Nacozari 75' > 'Fielder' = 'Fremont' > 'Glenson 81 '. Tous les hybrides F, ont kt6 stables sur le plan somatique. De nouvelles combinaisons ont kt6 faites avec A. curvifolium (Thinopyrum curvifolium), A. rechingeri (T. sartorii = rechingeri), A. scythicum (T. scyticum) et A. stipaefolium (Pseudoroegeneria stipaefolia). Tous les hybrides se sont avkrks vivaces et posskdaient un phknotype intermkdiaire entre les parents impliquks dans les combinaisons hybrides, mais avec une variation majeure dans la morphologie de l'kpi, soit des kpis allongks avec des entrenoeuds inkgaux. Les hybrides dont les appariements furent klevks, prksumkment en raison de la suppression du locus Ph, ont kt6 ceux de T. aestivum -A. scythicum (1 5,3 1 I + 2,25 I1 (en anneaux) + 6,92 11 (en bitonnets + 0,32) et de T. aestivum -A. stipaefolium (10,6 I + 7,08 I1 (en anneaux) + 4,41 I...
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