Male fertility restoration of wheat in Hordeum chilense cytoplasm is associated with 6HchS chromosome addition

We report a new cytoplasmic male sterility (CMS) source in bread wheat (Triticum aestivum L.) designated as msH1. CMS has been identified during the process of obtaining alloplasmic bread wheat in different Hordeum chilense Roem. Schultz. cytoplasms. It was observed that when using the H. chilense H1 accession, the corresponding alloplasmic line was male sterile. This alloplasmic wheat is stable under different environmental conditions and it does not exhibit developmental or floral abnormalities, showing only slightly reduced height and some delay in heading. On examining microsporogenesis in the alloplasmic line, it was found that different stages of meiosis were completed normally, but abnormal development occurred at the uninucleate-pollen stage at the first mitosis, resulting in failure of anther exertion and pollen abortion. Fertility restoration of the CMS phenotype caused by the H. chilense cytoplasm was associated with the addition of chromosome 6HchS from H. chilense accession H1. Thus, some fertility restoration genes appear to be located in this chromosome arm. Considering the features displayed by the msH1 system, we consider that it has a great potential for the development of viable technology for hybrid wheat production.

Presence of various rye-specific repeated DNA sequences on the midget chromosome of rye

The chromosome 1R of rye, or the midget chromosome, is necessary for plump, viable seed development and fertility restoration in the alloplasmic line with rye cytoplasm and a hexaploid wheat nucleus. The midget chromosome of rye represents 1/15th of the physical length of the chromosome 1R of rye. C-banding analysis indicated that the centromeric and pericentric region (approximately 30% physical length) of the midget chromosome is heterochromatic and the distant 70% physical length is euchromatic. These data suggest that the midget chromosome may represent the pericentric region of the long arm of chromosome 1R. In contrast with earlier reports, our results indicate that an array of rye-specific repeated sequences (both dispersed and tandem) are present on the midget chromosome. Various rye-specific repeated DNA sequences that are present on the midget chromosome will be useful in constructing a long-range map and studying the genomic organization of the midget chromosome. It is unclear if any of these repeated DNA sequences are involved in the origin of the midget chromosome.Key words: midget chromosome, pericentric region, repeated DNA sequences, rye telomere associated sequence.

Correction of chlorophyll deficiency in alloplasmic male sterile Brassica juncea through recombination between chloroplast genomes

SummaryBrassica juncea cv. Pusa Bold carrying B. oxyrrhina cytoplasm (oxy cytoplasm) was male sterile and chlorotic under field conditions at low temperature (Prakash & Chopra, 1990). Leaf protoplasts of the chlorotic male sterile alloplasmic line (2n = 36) were fused with hypocotyl protoplasts of green male fertile, B. juncea cv. RLM-198 (2n = 36) using polyethylene glycol. Of the 1043 plants regenerated from 10 fusion experiments, 123 had ‘gigas’ features and were identified as presumptive fusion products. Among field-grown population, one plant was dark green even at low temperatures and male sterile. It possessed 72 chromosomes which formed 36 bivalents at late diakinesis of meiosis-I. This plant was back-crossed to B. juncea cv. Pusa Bold (the maintainer line) for three successive generations. One male sterile, normal green BC3 progeny plant with 2n = 36 was analyzed for organelle constitution. Probing its total DNA with the mitochondrial gene for cytochrome oxidase subunit I revealed that it possessed mitochondria of B. oxyrrhina. Southern hybridization pattern with the gene for ribulose bisphosphate carboxylase oxygenase-large subunit (rbcL) revealed that the chloroplast genome of the chlorophyll deficiencycorrected plant had characteristics of both B. juncea and B. oxyrrhina. The deficiency correction has been attributed to recombination between chloroplast genomes of the two species.

MALE STERILITY-FERTILITY RESTORATION SYSTEMS IN TRITICUM DURUM

Triticum durum Desf. selection 56-1 (2n = 28,AABB) genomes were introduced into the cytoplasms of six species of Triticum, 14 of Aegilops, and one each of Secale and Haynaldia by the backcross method. Of the 22 alloplasmic lines, 14 were completely male sterile, four were partially fertile, and the remaining four, having cytoplasms of T. dicoccoides Körn, Ae. kotschyi Boiss., Ae. variabilis, Eig. or H. villosa L., were of normal fertility. Eleven of these lines headed late and 14 had lower plant height than the control euplasmic T. durum. The 14 male-sterile lines were crossed with five R-lines derived from crosses involving T. nudiglumis Nabalek and T. durum, and male-fertility restoration in F1 hybrids was examined. All five R-lines restored male fertility to six of the male-sterile lines having cytoplasms of Ae. speltoides Tausch., Ae. bicornis Forsk., T. nudiglumis, T. araraticum Jakubz., T. timopheevi Zhuk., or T. zhukovskyi Men. &Er. The male fertility of the alloplasmic line having rye (secale cereale L.) cytoplasm was completely restored by RE 5 and partially by RE 2. Also, RE 5 restored plant vigor to durum plants having rye cytoplasm. None of the five R-lines restored male fertility or plant vigor to any of the six male-sterile lines having cytoplasms of T. boeoticum Boiss., Ae. caudata L., Ae. umbellulata Zhuk., Ae. heldreichii Holzm., Ae. sharonensis Eig., or Ae. triaristata Willd. In general, F2 data from crosses involving four of the male-sterile lines and five R-lines indicated that male fertility restoration was simply inherited.