Assessment of genetic variability of haploids extracted from tetraploid (2n = 4x = 48) Solanum tuberosum.

The objectives of this study were to assess the genetic variability of haploids (2n = 2x = 24) extracted from tetraploid Solanum tuberosum through 4x x 2x crosses with Solanum phureja. Molecular and phenotypic analyses were performed to fingerprint the genotypes used and to evaluate their potential use in breeding programs. AFLP analysis revealed the presence of specific bands derived from the tetraploid seed parent S. phureja, as well as ex novo originated bands. On average, 210 bands were visualized per genotype, 149 (70%) of which were common to both parental genotypes. The percentage of S. tuberosum specific bands ranged from 25.1% to 18.6%, with an average of 22%. The fraction of genome coming from S. phureja ranged from 1.9% to 6.5%, with an average value of 4%. The percentage of ex novo bands varied from 1.9% to 9.0%. The presence of S. phureja DNA is very interesting because it indicated that S. phureja pollinator is involved in the mechanism of haploid formation. The characterization for resistance to Erwinia carotovora subsp. carotovora and potato virus X (PVX) provided evidence that haploids may express traits that are lacking in the tetraploids they come from, which can be useful for both genetic studies and breeding purposes. It is noteworthy that genotypes combining resistance to both diseases and good pollen stainability were identified. Other possible breeding implications owing to the presence of S. phureja genome in the haploids analyzed are discussed.     

Evidence for the existence of 2n gametes in Lotus tenuis Wald. et Kit. (2n=2x=12): their relevance in evolution and breeding of Lotus corniculatus L. (2n=4x=24)

Summary Crosses between male sterile L. corniculatus (2n=4x=24) and L. tenuis (2n=2x=12) plants were performed in order to verify the presence of 2n gametes in L. tenuis. All but one of the plants from these crosses had 2n=4x=24 and the L. corniculatus phenotype; this plant had 2n=2x=12 and the L. tenuis phenotype. The plants also showed good quantity of pollen at tripping, good pollen fertility and good percentage of seed setting in the backcross to L. corniculatus. On the whole, both cytological and morphological observations, showing that all but one of the plants from L. corniculatus x L. tenuis were normal tetraploids, suggest the existence of diploandrous gametes in L. tenuis. On the other hand, haploid parthenogenesis probably gave origin to the dihaploid plant 2n=2x=12.     

Features of the formation of self-fertile euploid lines (2n = 42) by self-pollination of the 46-chromosome barley-wheat BC1 hybrid Hordeum marinum subsp. gussoneanum Hudson (= H. geniculatum All.) (2n = 28) x Triticum aestivum L. (2n = 42)

We studied some features of the development of self-fertile 42-chromosome lines on the base of self-pollination progeny of 46-chromosome plants obtained by backcrossing of barley--wheat hybrids Hordeum marinum subsp. gussoneanum Hudson (= H. geniculatum All.) (2n = 28) x Triticum aestivum L. (2n = 42). The stabilization of karyotypes, resulting in 42-chromosome plants of the wheat type was generally completed by generation BC1F10. The plants of all self-pollination progenies, including BC1F10, showed some phenotypic traits characteristic of wild barley. Plants of BC1F10 with the chromosome sets 2n = 42 and 2n = 42 + t were analyzed by RAPD with a set of 115 primers. Fragments of the wild barley genome were detected in RAPD patterns with 19 primers. Cross-hybridization confirmed that these fragments belonged to the wild barley genome. We raised four phenotypically different 42-chromosome lines from grains obtained from plants of generation BC1F10, and these lines proved to be cytogenetically stable and self-fertile when grown in the field.     

Molecular study and C-banding of chromosomes in common wheat alloplasmic lines obtained from the backcross progeny of barley-wheat hybrids Hordeum vulgare L. (2n = 14) x Triticum aestivum L. (2n = 42) and differing in fertility

We studied common wheat alloplasmic lines differing in fertility traits, which had been obtained from the backcross progeny of barley-wheat hybrids Hordeum vulgare L. (2n = 14) x Triticum aestivum L. (2n = 42), using molecular analysis and chromosome C-banding. It was found that the nuclei of all alloplasmic lines studied, regardless of their fertility traits, contained only the common wheat chromosomes (2n = 42). The formation of line L-79(10)(3)F6, stable for self-fertility, from line L-79(10)(3)F6 was accompanied by changes of the proportions of simple sequence repeats of the parental common wheat varieties in the nuclear genome. The presence of barley genome fragments in line accessions with incomplete self-fertility was shown by RAPD. Heteroplasmy for mitochondrial genome loci was detected in these lines with the use of primers specific to the tMet-18S-5S repeat of mitochondrial ribosomal genes.     

Use of Ipomoea trifida germ plasm for sweet potato improvement. 3. Development of 4x interspecific hybrids between Ipomoea batatas (L.) Lam. (2n=6x=90) and I. trifida (H.B.K) G. Don. (2n=2x=30) as storage-root initiators for wild species

Summary More than 28,000 pollinations were carried out between 5 Ipomoea batatas and 41 diploid I. trifida accessions of diverse origins to obtain 4x interspecific hybrids. From the resultant 730 seeds, 248 plants were finally obtained. Ploidy level determination of the progeny showed unexpected results: 52 individuals were hexaploid, 5 were pentaploid, 190 were tetraploid, as expected, and one was not determined. The existence of 5x and 6x progenies from 6x x 2x crosses not only confirmed the presence of 2n gametes but also their successful function in gene flow between ploidy levels and polyploidization within this genus. The progeny and their cultivated parents were planted in an observation field. The cultivated parents produced 0.49 kg/plant or less. Most 4x progenies did not produce storage roots or had very poor yields; nonetheless, and despite their cultivated parents' poor yields, 8 genotypes yielded between 0.81 and 1.50 kg/plant.A new scheme, using the 4x interspecific hybrids, is proposed for evaluating 2x and 4x wild accessions of the section Batatas to which the sweet potato belongs. Other possible uses of the 4x hybrids in breeding and genetics of the sweet potato are also discussed.     

Study of mitochondrial genomes of allopllasmic recombinant wheat lines constructed on the basis of barley-wheat hybrids Hordeum geniculatum all. (= H. marinum subsp. gussoneanum) (2n = 28) x x Triticum aestivum L. (2n = 42) with using of RELP and PCR analyses

Using RELP analysis with three probes homologous to specific regions of mitochondrial DNA genes and PCR analysis of the mitochondrial recombining-repeat-sequence 18S/5S region of cereals, five alloplasmic wheat lines of different origin and fertility expression were studied. These lines are self-pollinated progeny of BC1-BC4 generations of barley-wheat hybrids Hordeum geniculatum All. (2n = 28) x Triticum aestivum L. (2n = 42). It was found that recombinant alloplasmic lines characterized by partial fertility contain either maternal (barley) DNA fragments or maternal and paternal (wheat) DNA fragments simultaneously (heteroplasmy). In lines with stable expression of self-fertility, fragments of only paternal mitochondrial DNA were detected. It is assumed that in alloplasmic lines, there is the interrelation between the presence of definite fragments of the mitochondrial genome belonging to either parental type and fertility expression.