Majority Of Progeny Research Articles

"Establishment of GISH and multi-color GISH techniques to simultaneously discriminate different genomes in Erianthus procerus x Saccharum officinarum introgressed clones "

An attempt was made to identify the chromosomes from different species genomes in BC₂ progenies of Erianthus procerus x Saccharum officinarum through multi-color GISH (MCGISH). The BC₂ population was derived from the cross between a BC1 hybrid (GU 12-14) and a commercial variety, Co 16018. The BC2 progenies were studied for their somatic chromosome number and two cytotypes were observed, i.e., 2n=92 (2) and 2n=96 (5). GISH revealed that the majority of progenies were having nine Erianthus chromosomes, except 2 clones (25-5 and 25-10) were having nine Erianthus chromosomes with one chromosome fragment. The methodology for multi-color GISH was standardized and it distinguished the chromosomes from different genomes. Interspecific recombination was also detected in somatic cells of one BC₂ clone, 25-10. The hybridity of the introgressed lines has been confirmed with amplification of Erianthus specific tandem repeat sequences.

Spawning kinetics and parentage contribution of European sea bass (Dicentrarchus labrax) broodstocks, and influence of GnRHa-induced spawning

Increasing parentage contribution in aquaculture broodstocks is important, in order to take full advantage of the available genetic makeup of the chosen fish, and to avoid inbreeding and loss of allele diversity over subsequent production generations. European sea bass (Dicentrarchus labrax) broodstocks were evaluated over two reproductive seasons to examine spawning kinetics, egg production, and parentage contribution during spontaneous/volitional spawning. In addition, we obtained preliminary results on the potential of a hormonal therapy to synchronize spawning and increase parentage contribution. Spawning lasted between 25 and 66 days in January-March and consisted of 12–21 daily spawns per broodstock, with individual females spawning 1–5 times and males participating in 1–8 spawns during each reproductive season. Daily fecundity was variable during the season, without any trend, and so were all the examined egg/larval quality parameters. Parentage assignment of the produced families indicated that the majority of progeny from a whole season may belong to a very small number of breeders, with four females producing up to 80 % of the analyzed eggs, while a single male may sire up to 57 % of the fertilized eggs. No significant improvement in the overall parentage contribution was obtained with the hormonal treatment, using gonadotropin releasing hormone agonist (GnRHa). Nevertheless, the daily fecundity was higher, and parentage of the eggs from the first spawn after GnRHa treatment was more equally distributed to multiple males/females, compared to any volitional spawns. The study demonstrates the need to further improve parentage contribution in European sea bass aquaculture, through synchronization of maturation and spawning. Although the GnRHa induction experiment was not replicated in the present preliminary study, the results suggest that hormonally-induced synchronization of maturation may have the potential of producing a larger number of progenies from more families, from where to select the next generation of breeders for a breeding program.

A cross-eyed geneticist’s view VI. Segregation distortion in Drosophila melanogaster: Recent progress in solving ‘an esoteric puzzle’

Segregation distortion refers to an unusual genetic phenomenon in diploid organisms by which the two alleles at a locus in a parent are not recovered in the classical 1:1 Mendelian ratio in its offspring. The Drosophila melanogaster neogene Sd was created by a duplication breakpoint on the left arm of chromosome 2 (2L), and encodes a truncated RanGAP protein with normal GTPase activity but which mis-localizes to the nucleus and disrupts Ran gradients. Male flies carrying Sd exhibit segregation distortion for the Rsp locus on the right arm of chromosome 2 (2R). Specifically, spermatids inheriting chromosome 2 with the Sd+ Rsps(s) genotype, in heterozygous males of genotype Sd Rspi/ Sd+ Rsps(s), fail to develop properly so that the majority of progeny (approaching 100%) carry just the Sd Rspichromosome. One recent paper reported novel RNAi-expressing transgenes with Sd-mimicking properties; and another reported localization of an X-linked suppressor which restores Mendelian transmission. This article highlights how Drosophila genetics resources made this possible, and the significance of these findings to nucleus-cytoplasm transactions of interest to the wider cell biology community.

Genetic Pedigree Analysis of the Pilot Breeding Program for the Rediscovered Galapagos Giant Tortoise from Floreana Island.

An aim of many captive breeding programs is to increase population sizes for reintroduction and establishment of self-sustaining wild populations. Genetic analyses play a critical role in these programs: monitoring genetic variation, identifying the origin of individuals, and assigning parentage to track family sizes. Here, we use genetic pedigree analyses to examine 3 seasons of a pilot breeding program for the Floreana island Galapagos giant tortoise, C. niger, that had been declared extinct for ~150 years until individuals with mixed ancestry were recently discovered. We determined that 8 of 9 founding individuals were assigned parentage to at least 1 of 130 offspring produced, though there was considerable reproductive skew. In addition, we observed that genetic diversity of the progeny was lower than that of the founders. Despite the observed reproductive skew, we did not see evidence for assortative mating based on relatedness, but there was a trend toward reduced fitness when more related individuals bred. Finally, we found that the majority of progeny had ancestry assigned to the Floreana species (mean ± SE = 0.51 ± 0.02), though individual estimates varied. The success of these pilot seasons bodes well for a larger breeding program to help restore the previously extinct tortoise from Floreana island. Future efforts should continue to monitor for reproductive skew and assortative mating to maintain allelic diversity. We would also recommend forming smaller breeding groups and rotating individuals among them to prevent long-term reproductive skew among pairs.

Increased anthocyanin content in purple pericarp × blue aleurone wheat crosses

AbstractDue to their antioxidant activity, anthocyanins are of increasing interest for nutritionists, food scientists and plant breeders. Anthocyanins in wheat grains are expressed in either the pericarp or aleurone layer. Previous studies revealed that different anthocyanins are present in wheat varieties carrying genes for either the purple pericarp or the blue aleurone trait. Progeny from crosses between red‐, purple‐ and blue‐grained wheat varieties were selected over several cycles for grain colour by visual scoring. Bulked F5 grains were evaluated for their total anthocyanin content by UV‐VIS spectrophotometry and HPLC‐MS. The results demonstrate that it is possible to increase the anthocyanin content by the combination of the different genetic backgrounds for purple pericarp and blue aleurone, even though the majority of progeny were within the range of the purple‐ and blue‐grained check varieties. Visual scoring for grain colour is efficient, reliable and fast for selection in early breeding generations. Advanced breeding lines with high anthocyanin content can be identified by simple extraction methods and spectrophotometric measurements.

DISPERSION OF CRYPHONECTRIA PARASITICA VEGETATIVE COMPATIBILITY GROUPS IN A CHESTNUT STAND COMPOSED OF DIFFERENT PROGENIES

In 2003 and 2006 occurrence and dispersion of vegetative compatibility groups (VCGs) of chestnut blight fungus, Cryphonectria parasitica, was investigated in the stand of 270 chestnut seedlings, 20-year-old, belonging to different progenies. Majority of progenies were derived from controlled intra-specific crosses C. sativa × C. sativa and open pollinated C. sativa trees. Three progenies were derived from interspecific crosses C. sativa × C. crenata. Between 2003 and 2006, the portion of blighted stems rose from 7% to about 19%. Among 79 isolate, a total of seven VCGs were detected (EU 5, EU 12, EU 13, EU 15, EU 16, EU 17, EU 2). In 2003 was missing EU 2 and in 2006 EU 15 type. The same two VCGs (EU 5, EU 13) dominated in both surveyed years comprising nearly 70% of all isolates. Dispersion pattern of individual VCGs was analysed by Mantel test based on correlation of two matrices. One matrix contained the Gower distances between trees with cankers of the same VCG and the other one contained estimates of Euclidean distance between all blighted trees with VCGs assigned at random. Results have pointed at significantly non- random dispersion of VCGs in both surveyed years. Aggregation of VCGs strongly correlated with the origin of blighted trees. Progenies derived from three mother trees C. sativa of home origin exhibited significantly higher infection rate (from 42 to 50%) than remaining progenies. Only one blighted tree was found in 2006 among 20 inter-specific hybrids.

Relevance of unilateral and bilateral sexual polyploidization in relation to intergenomic recombination and introgression in Lilium species hybrids

Sexual polyploids were induced in diploid (2n = 2x = 24) interspecific F1 hybrids of Longiflorum × Asiatic (LA) and Oriental × Asiatic (OA) Lilium hybrids by backcrossing to Asiatic (AA) parents as well as by sib-mating of the F1 LA hybrids. A majority of the BC1 progenies were triploid and the progenies from sib-mating were tetraploid or near tetraploids. Genomic in situ hybridization (GISH) technique was applied to assess the intergenomic recombination in the BC1 populations of LA and OA hybrids obtained after unilateral sexual polyploidization. A total of 63 LA (LA × AA and AA × LA) and 53 OA hybrids were analysed. LA hybrids were originated through the functioning of 2n gametes either as 2n eggs or 2n pollen while those of OA hybrids originated through functional 2n pollen of diploid OA genotype. In both type of crosses, a majority of the progenies had originated through First Division Restitution (FDR) mechanism of functional 2n gamete either with or without a cross over. However, there were nine LA- and four OA-genotypes where Indeterminate Meiotic Restitution (IMR) was the mechanism of 2n gamete formation. Based on GISH, total amount of introgression of Longiflorum and Oriental genome into Asiatic genome was determined. Most of the BC progenies exhibited recombination and the amount of recombination was higher in LA hybrids as compared to OA hybrids. Intergenomic recombination was also determined cytologically in the 16 plants of sib-mated LA hybrids where both parents had contributed 2n gametes. Based on these results the nature of interspecific lily hybrids obtained from uni- and bilateral sexual polyploidization leading to allotriploid and allotetraploid formation is discussed in the context of introgression and intergenomic recombination.

Microsatellite markers reveal low breeding system efficacy and pollen contamination can limit production of full-sib avocado progeny

Phytophthora cinnamomi causes a severe root rot in avocado, Persea americana. Breeding tolerant rootstocks is thought to be the most promising method for phytophthora root rot disease control but breeding avocado is challenging. The avocado flowering syndrome (synchronous protogynous dichogamy), combined with high flowering and low fruit set, render controlled pollination exceedingly difficult. Juxtaposing complementary flowering types of elite parent cultivars (cultivars that produce progeny with tolerance to phytophthora root rot) was performed in an effort to increase the number of full-sib progeny for elite maternal parents and, hypothetically, the number of phytophthora root rot tolerant progeny. Although high outcrossing rates were achieved (estimated ∼93%), the majority of progeny had a non-elite paternal parent (56% of progeny were offtypes) implying maternal trees were pollinated by non-elite distant trees. Among progeny that could be confidently genotyped, a high number of cross types were detected (33). Contrary to our hypothesis, a significant portion of the progeny were the result of crosses between like, and not complementary, flowering types. The spatial distribution of productive trees and grafts helped to explain these data, as productive grafts were directly adjacent to grafts of the same flowering type more often than that of the complementary flowering type. Selfed progeny were significantly less tolerant to phytophthora root rot than outcrossed progeny. Progeny resulting from crosses between an elite maternal parent and non-elite pollen donor (offtypes) were less tolerant than full-sib progeny resulting from crosses between elite parents. Maternal effects may interfere with identifying truly disease tolerant selections. Thus, to reduce maternal effects and non-elite pollen donor contamination, removal of seedling cotyledons before screening for disease tolerance and better isolation of elite parent trees and windbreaks may improve breeding efficacy. This study also demonstrates the usefulness of microsatellite markers in parentage analysis where a high proportion of the putative parents are closely related.

Quantitative determination of mosaic GFP gene expression in tobacco.

A specific form of gene silencing that was observed visually as a mosaic distribution of fluorescent and non-fluorescent cells apparently dispersed at random within tissues was found in a few green fluorescent protein (GFP)-transformed tobacco lines. To characterize this event quantitatively, we studied flow cytometric measurements in GFP-expressing and -silenced cells in T1 and T2 progeny of four selected plants. The proportion of silenced cells varied considerably among the T1 lines but with notable genotype differences. Mosaic expression was inherited into the T2 generation in which the majority of progenies tested exhibited a level of silencing similar to that of their T1 parental plants. However, in some T2 progenies segregation, evident as a decrease or increase in the proportion of fluorescent cells, was observed. We discuss several factors, such as copy number, promoter activity or polyploidy, that may be the possible causes of the gene silencing, but none sufficiently explain the appearance of the mosaic distribution.

Inactivation of the Murine Pyruvate Dehydrogenase (Pdha1) Gene and Its Effect on Early Embryonic Development

A deficiency of pyruvate dehydrogenase complex (PDC) in humans results in lactic acidosis and neurological dysfunction that frequently results in death during infancy. Using gene targeting technology, a silent mutation was introduced into the murine X-linked Pdha1 gene that encodes the α subunit of the pyruvate dehydrogenase or E1 component of the complex. Two loxP sequences were introduced into intronic sequences flanking exon 8 to generate the Pdha1flox8 allele. In vitro studies in embryonic stem cells demonstrated that deletion of exon 8 ablated PDC activity. Homozygous Pdha1flox8 females were bred with male mice carrying a wild-type Pdha1 allele and a transgene that ubiquitously expresses the Cre recombinase to produce progeny with a deletion in exon 8, Pdha1Δex8. The majority of progeny were found to be mosaic with the presence of both the flox and deleted alleles, and there were no apparent phenotypic effects associated with the null allele. The mosaic mice were interbred to increase the degree of mosaicism for the Pdha1Δex8 allele in the subsequent generation, resulting in a significantly smaller litter size (54% reduction). Embryos carrying predominantly the Pdha1Δex8 allele were found to be globally delayed in development by 9.5 days postcoitus, with resorption occurring over the following several days. These findings demonstrate an essential role for oxidative metabolism of glucose during the early postimplantation period of prenatal development.

Conditional mutagenesis in mice with heat shock promoter-driven cre transgenes.

To explore the potential of a simple and rapid approach for ubiquitous conditional gene disruption, we have generated Cre-producer mouse transgenic lines (Hs-cre1, 6 and 7) expressing a recombinase transgene (cre) from a heat shock gene promoter and tested their performance in Cre-mediated excision of target DNA in crosses with Cre-responder strains carrying loxP-modified alleles of the genes encoding the Huntington's disease gene homolog (Hdh), the epidermal growth factor receptor (Egfr), and the type 1 insulin-like growth factor receptor (Igf1r). Analyses of progeny possessing various transgene/reporter combinations showed that cre expression can occur without heat shock in early embryos, but this constitutive transcription is stochastic and transgene dependent. Thus, Hs-cre1 behaves predominantly as a "deleter" strain, since the majority of progeny (approximately 70-85%) exhibit complete recombination, regardless of reporter locus. Lines Hs-cre6 and Hs-cre7, however, function successfully as "mosaicking" strains because, in addition to two extreme classes of progeny with 0% or 100% recombination, they generate an intermediate class of mosaics exhibiting various degrees of partial DNA excision. Notably, the frequency of offspring in each class varies between reporters, but mosaic embryos are consistently obtained in adequate numbers (approximately 30-60%). The Hs-cre6 transgene is also inducible and can be used to introduce mosaicism into adult tissues at preselected developmental times by heat shock treatment of mice with 0% recombination in tail DNA. By bypassing the lethality resulting from some gene knockouts, mosaic embryos and mice make particular mutational analyses possible and are also very useful for the identification of cell lineage-specific gene functions.

The genetics of rust resistance in sugar cane seedling populations

The inheritance of rust resistance was studied in sugar cane seedling populations using a factorial mating design over 1 summer and 2 winter seasons. Frequency distributions for rust infection pooled over 2 winter seasons for resistant x resistant parents were highly skewed with the majority of progenies grouped towards the resistant classes, whereas crosses between susceptible x highly susceptible parents tended to be skewed with the majority of progenies grouped towards the susceptible ones. Both categories of crosses produced transgressive segregants at either extremes. Distribution of infection within progeny of the selfed resistant parent ’R 570’ and distribution in the majority of crosses tended to support the hypothesis of a major gene with a dominant effect for resistance. However, the action of other minor genes acting in a quantitative way is also suggested. The female (F) and male (M) variance components were very important, and F×M interaction indicated the existence of non-additive genetic effects. F×S, M×S and F×M×S interaction mean squares were generally low or insignificant. Broad-sense heritability for the individual season ratings and for the combined ratings was high (0.75–0.90), whereas narrow-sense heritability was generally moderate (0.40–0.52) with the additive genetic effects accounting for 44–68% of the total genetic variation. The implications of these findings in the breeding for rust resistance in the local programme are discussed.

Spatial distribution, fruit production and seed removal of a rare, dioecious canopy tree species (Aglaia aff. flavida Merr. et Perr.) in Papua New Guinea

ABSTRACTAll mature individuals of Aglaia aff. flavida (Meliaceae) were mapped in a 260 ha study area at the Crater Mountain Biological Research Station in Papua New Guinea. Sixty-four reproductively mature trees were found in an aggregated distribution with a mean inter-tree distance of 88.9 m. The sample consisted of 35 female and 29 male trees with a mean shortest distance between sexes of 232 m. Seed production and seed removal of 22 female trees was monitored throughout the 1992 fruiting season. Female trees with in 200 m of male trees generally produced large seeds crops (> 100 seeds) whereas trees farther than 200 m from the nearest male had small seed crops (< 100 seeds) regardless of female size (DBH). Most seeds (63.2%, n = 3312) produced in a sub-sample of 22 trees came from the five most fecund trees, which also produced 74.1% of the seeds that were removed by vertebrate dispersers. Where a minority of a population of rare tropical trees produce the majority of progeny, sustainable harvest practices would be most effective where highly fecund individuals are identified and conserved.

Inheritance and Linkage of Thirteen Polymorphic Isozyme Loci in Diploid Blueberry

Diploid populations and progenies of controlled crosses of blueberry, Vaccinium section Cyanococcus, were analyzed by starch gel electrophoresis for nine enzyme systems, aconitase (ACO), aldolase (ALD), alcohol dehydrogenase (ADH), glyceraldehyde-3 -phosphate dehydrogenase (G-3-PDH), isocitrate dehydrogenase (IDH), leucine aminopeptidase (LAP), malate dehydrogenase (MDH), 6-phosphogluconate dehydrogenase (6-PGD), and phosphoglucose isomerase (PGI). Allozyme variants indicated the existence of three alleles at Ace-1, Ald, G-3-pdh-2, and Mdh-2; four alleles at Mdh-3 and 6-Pgd-2; five alleles at Aco-2, Idh, Lap-1, and 6-Pgd-1; six alleles at Adh-2 and Pgm-2; and nine alleles at Pgi-2. In addition, a null allele was found at Lap-1. In the majority of progenies, the inheritance patterns for each of these loci were consistent with mendelian laws for single gene control. Forty-seven pairs of loci were tested for independent assortment revealing two linked pairs, Pgi-2/Lap-1 and Pgm-2/6-Pgd-2, which appeared to represent two independent linkage groups.

CYTOGENETICS OF <i>SCILLA SCILLOIDES</i> COMPLEX

1. Several types of hypo- and hyper-ploids were found along with euploids BB, BBB, ABB, AABB, and ABBB among plants from a natural population of Scilla scilloides Druce at Nakabaru. Here A (x=8) indicates one of two genomes which compose the S. scilloides complex, and B (x=9) another one. Lacking or additional chromosomes in hypo- and hyper-ploids, ABB-1, -2, ABB+1, +2, +3, +5, AABB-1, -2, -3, were confirmed to be members of the genome A.2. The majority of progenies from seeds collected from ABB open-pollinated in the natural population was hypo- and hyper-ploid. Hypo- and hyper-ploids were also found in the progenies from the seeds from the mother plants BB and AABB. These facts indicate frequent occurrence of selfing of, and/or crossing between ABB, as well as crossing of ABB with BB and/or AABB. Therefore, ABB is primarily responsible for the origin of hypo- and hyper-ploids in the natural population.