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PubMed2002

Identification of an STMS marker for the double-podding gene in chickpea.

Chickpea, a self-pollinating diploid annual with 2n = 2 x = 16 chromosomes, is an important food legume crop throughout the world and especially in developing countries. A gene that confers double-podding, with the symbol " s", is considered important for breeding higher yielding cultivars. Positive effects of " s" on yield stability were found by comparing single- and double-podded near-isogenic lines (NILs) derived from a cross of CA-2156 (single-podded) with JG-62 (double-podded). Considering the significant effects on seed yield, the NILs were used to identify molecular markers closely linked to " s". Sequence tagged microsatellite site (STMS) markers developed for chickpea, random amplified polymorphic DNA (RAPD) and inter simple sequence repeat (ISSR) markers were used to analyze the NILs. Out of 400 RAPD, 100 STMS and 100 ISSR markers, one STMS marker (TA-80) was polymorphic and was used to evaluate a recombinant inbred line population developed from the cross of Surutato-77 (single-podded) x JG-62 (double-podded) for co-segregation of the locus with " s". Our results indicated that the marker and " s" were 4.84 cM apart. This marker may be used by breeders for marker-assisted selection (MAS) to monitor the incorporation of the double-podding gene into improved germplasm.

Journal Article↗
PubMed2002

High-resolution genetic map of Nb, a gene that confers hypersensitive resistance to potato virus X in Solanum tuberosum.

Nb is a single dominant gene in potato that confers hypersensitive resistance to potato virus X (PVX) isolates from strain groups 1 and 2. Genetic and molecular analyses showed that Nb is located on the upper arm of chromosome V and forms part of a cluster of resistance genes encoding specificities to many different pathogens. We describe the genetical localisation of molecular markers tightly linked to the Nb locus and the development PCR-based markers suitable for isolation of the Nb resistance gene by positional cloning. A bulked segregant approach was applied to identify polymorphic AFLP markers tightly linked to the Nb locus. These markers were mapped in a population of segregating S1 progeny (1,300 plants) from a self-pollinated potato cultivar, Pentland Ivory. From this analysis, Nb was placed in an interval of 0.76 cM, flanked by the AFLP markers GM339 and GM637. Recombinant PVX strains carrying different combinations of avirulence genes were used in biological assays to show that Nb was also present in potato cv. Cara but was masked by the extreme PVX resistance conferred by the Rx gene. PCR-based screening of a Cara genomic BAC library with markers closest to the Nb locus identified a new marker tightly linked to Nb.

Journal Article↗
PubMed2002

Inheritance of S(f)-RNase in Japanese apricot ( Prunus mume) and its relation to self-compatibility.

Self-compatible cultivars of Japanese apricot ( Prunus mume Shieb. et Zucc.), a tree species that normally shows S-RNase-based self-incompatiblity, have a horticultural advantage over self-incompatible cultivars. Inheritance of self-compatibility and a common S(f)-RNase allele that is observed in self-compatible cultivars was investigated using progenies from controlled crosses. Total DNAs were isolated from the parents and progenies of seven crosses that included at least one self-compatible cultivar as a parent. These DNAs were PCR-amplified with the Pru-C2 and PCE-R primer pair to determine S-haplotypes of the parents and progenies. A novel S-haplotype, S(8), was found. In all crosses examined, the S(f)-RNase gene was inherited from either the seed or pollen parent as a pistil S-allele in a non-functional S-haplotype. Self-compatibility of about 20 trees each from reciprocal crosses of 'Benisashi ( S(7) S(f))' and 'Shinpeidayu ( S(3) S(f))', and 26 selections from 16 different crosses was tested by pollination and pollen-tube growth studies. Cosegregation of the S(f)-RNase allele and self-compatibility was confirmed with all but selection 1K0-26 ( S(3) S(7)). Selection 1K0-26 ( S(3) S(7)) that originated from 'Benisashi ( S(7) S(f))' x 'Koshinoume ( S(3) S(f))' appeared to be self-compatible even without the S(f)-RNase allele. The possible role of pollen- S, a presumably existing pollen component of gametophytic self-incompatibility, is discussed.

Journal Article↗
PubMed2002

Expression and inheritance of the wheat Glu-1DX5 gene in transgenic maize.

We have produced transgenic maize plants containing a wheat Glu-1Dx5 gene encoding the high-molecular-weight glutenin subunit 1Dx5. Analysis by SDS-PAGE showed that a protein similar in size to the wheat 1Dx5 subunit accumulates in the endosperm of transgenic maize from four independent transformation events. This protein reacts with a monoclonal antibody specific to the wheat 1Dx5 subunit and was not detected in nontransgenic controls or in pollen, anthers, leaves or embryos of plants grown from seeds expressing this protein in endosperm. Genomic Southern-blot analysis is consistent with results from SDS-PAGE and indicates that the transgene integration sites are complex and are different in the four events studied. Using the presence of this protein as a phenotypic marker, we studied the inheritance of this gene through three sexual generations. Reciprocal crosses with nontransgenic plants and self-pollinations were performed, and the resulting kernels were analyzed for the presence of the 1Dx5 subunit. These data, together with PCR analysis for the transgene, suggest that the transgene is inefficiently transmitted through pollen in all four events.

Journal Article↗
PubMed2002

Considerations of correlated fertility between genders on genetic diversity: the Pinus densiflora seed orchard as a model.

The correlation between 99 clone female and male fertilities in a first generation seed orchard of Pinus densiflora was studied over 6 years. The effective number of the parent ( N(p)) and the variance effective population number [ N(e)((v))] were used to assess the impact of total (Psi(T)), female (psi(f)) and male (psi(m)) fertility variation. A theoretical framework was developed to account for female and male fertility correlations as well as the impact of possible pollen contamination. Total fertility variation was described by the sibling coefficient (Psi(T): the probability that two genes randomly chosen from the gamete gene pool originate from the same parent), which was further subdivided into psi(f) and psi(m). These parameters were compared under various conditions including the total seed harvest, imposing on equal seed harvest among the orchard's clones and two contamination scenarios ( M = 0 and 20%). Fertility variations among females, males and clones were observed within and among years. Sibling coefficients (Psi(T)) were lower, but the effective number of parent ( N(p)) and variance effective population number ( N(e)((v))) were higher in years with moderate female and good male strobilus production. N(p) for female and male reproductive outputs varied from 49 to 82 and from 57 to 93, respectively. N(p) was higher for males than females. When the crop of the 6 years was pooled, N(p) for female, male and the clone were 73, 87 and 85, respectively. The impact of female-male fertility correlation for conditions with no-, positive- and negative-correlations were assessed and their impact on Psi(T), N(p) and N(e)((v)) was also evaluated. It was demonstrated that the practice of equal seed harvesting from every clone, or the mixing of seeds from several years, would substantially improve the genetic diversity and the genetic representation of the seed orchard population when a positive correlation between gender fertilities was observed. The relevance of these results to supplemental-mass-pollination was discussed under two cases where equal- and un-equal amounts of pollen from clones were included in the pollen mixes.

Journal Article↗
PubMed2002

Comparison between Poncirus and Citrus genetic linkage maps.

Five genetic linkage maps were constructed for the parents of three progenies: Citrus aurantium (A) x Poncirus trifoliata var. Flying Dragon (Pa), C. volkameriana (V) x P. trifoliata var. Rubidoux (Pv) and a self-pollination of P. trifoliata var. Flying Dragon (Pp). The number of polymorphic markers assayed ranged from 48 for Pa to 120 for A according to the heterozygosity of each parental. As our focus was on genome comparison, most of the markers were newly generated simple sequence repeats. Inter-retrotransposon amplified polymorphisms based on four retrotransposon sequences isolated from Citrus spp were also used to saturate the maps. These polymorphisms were much more frequent in A (53) than in Pa (15) and randomly distributed throughout both genomes. Since comparative genomics and quantitative trait locus analysis applicability depends on the reliability of marker ordering, the causes of variation in marker order were investigated. Around 25% of the markers showed gametal segregation distortions. Segregation distortions were also observed at the zygotic level towards a reduction in the observed frequency of homozygotes from that expected in linkage groups 5 and 7. The presence of balanced lethal factors or gametal incompatibility genes in those genomic regions would explain a zygotic advantage of heterozygotes at these specific regions. Four differences in genomic organization were observed; three are putative translocations and affect homeologous linkage groups 3, 7 and 11, where highly distorted markers are found. Other causes of variation in marker order are also discussed: the introduction of new markers in the map, lowering the LOD score and the mapping software. These results represent the first comparative mapping analysis among Citrus and Poncirus species.

Chromosome Mapping↗
PubMed2002

Pollen morphology and in vitro germination characteristics of nodulating and nonnodulating soybean (Glycine max L.) genotypes.

Artificial hybridization in highly self-pollinated crop species such as soybean (Glycine max L.) is important for both generating genetic variability and segregation for selection. In higher plants, pollen is an agent for transmission of genetic information over generations. The objective of this study was to measure and compare both morphological (length, width) and in vitro germination (germination percentage tube length) characteristics of pollen from the nodulating soybean cultivar, Bragg, and a nonnodulating Bragg mutant line, Nod 139, obtained following ethyl methanesulphonate treatment. Highly significant (P = 0.007) differences in pollen length were observed between these two genotypes. Similarly, in vitro germination percent (G%) indicated highly significant (P = 0.0001) differences between these genotypes, suggesting that the nodulation trait produces variation in in vitro germination capacity of the pollen. It appears the nonnodulation trait in soybean alters pollen grain length and G%.

Pollen↗
PubMed2003

Inheritance of self-compatibility in almond: breeding strategies to assure self-compatibility in the progeny.

To assure self-compatibility in the progenies, three different crosses were conducted for the first time in an almond breeding programme: self-pollination (266 descendants from 30 families), crosses between parents sharing an S-allele (108 descendants from five families) and crosses with homozygous self-compatible parents (62 descendants from five families). Depending on the cross, self-compatibility in the progenies was determined by observing pollen tube growth (by means of fluorescence microscopy), stylar S-RNases analysis or allele-specific PCR. The results obtained fit with the accepted hypothesis of inheritance of self-compatibility and the three crossing strategies used ensured 100% of self-compatible descendants. These strategies increase the efficiency of the breeding programme and avoid the laborious task of evaluating this characteristic. From the breeding point of view, self-fertilisation and crosses between relatives tend to produce inbreeding. Furthermore, these methods reduce the possibilities of choosing the parental combination. The use of homozygous self-compatible parents does not have any of these disadvantages. As far as we know, this is the first time that allele-specific PCR has been used for early selection of self-compatible seedlings. The advantages and disadvantages of the three methodologies used to determine self-compatibility are discussed.

Crosses, Genetic↗
PubMed2003

Development of rapeseed with high erucic acid content by asymmetric somatic hybridization between Brassica napus and Crambe abyssinica.

PEG-induced asymmetric somatic hybridization between Brassica napus and Crambe abyssinica was carried out. C. abyssinica is an annual cruciferous oil crop with a high content of erucic acid in the seed oil valuable for technical purposes. UV-irradiated mesophyll protoplasts of C. abyssinica cv 'Carmen' and cv 'Galactica' were fused with hypocotyl protoplasts of different genotypes of B. napus cv 'Maplus' and breeding line '11502'. Shoot regeneration frequency varied between 6.1% and 20.8% among the different doses of UV-irradiation, ranging from 0.05 J/cm(2) to 0.30 J/cm(2). In total, 124 shoots were regenerated, of which 20 asymmetric somatic hybrids were obtained and verified by nuclear DNA content and AFLP analysis. AFLP data showed that some of the characteristic bands from C. abyssinica were present in the hybrids. Cytological analysis of these hybrids showed that 9 out of 20 asymmetric hybrids had 38 chromosomes, the others contained 40-78 chromosomes, having additional chromosomes between 2 and 40 beyond the 38 expected for B. napus. The investigation into the fertility of asymmetric somatic hybrids indicated that the fertility increased with increasing UV-doses ranging from 0.05 J/cm(2) to 0.15 J/cm(2). All of the hybrids were cultured to full maturity, and could be fertilized and set seeds after self-pollination or backcrosses with B. napus. An analysis of fatty acid composition in the seeds was conducted and found to contain significantly greater amounts of erucic acid than B. napus. This study indicates that UV-irradiation could be used as a tool to produce asymmetric somatic hybrids and to promote the fertility of the hybrids.

Brassica napus↗
PubMed2003

Sequence variation and genomic organization of fatty acid desaturase-2 (fad2) and fatty acid desaturase-6 (fad6) cDNAs in maize.

Increased levels of oleic acid may enhance the nutritional and functional value of corn. Corn oil is primarily composed of palmitic, stearic, oleic, linoleic and linolenic fatty acids. Delta-12 desaturase in plants converts oleic acid (18:1) to linoleic acid (18:2) by inserting a double bond at the delta-12 position. Fatty acid desaturase-2 (fad2) encodes delta-12 desaturase that functions in the endoplasmic reticulum while fatty acid desaturase-6 (fad6) encodes delta-12 desaturase that functions in plastids. Complementary DNA (cDNA) clones from putative maize homologs for fad2 and fad6 were identified and the entire clones DNA sequenced. The maize fad2 cDNAs showed an amino-acid identity of 67-77% to fad2 of Glycine, Arabidopsis and Brassica species. Our cDNA sequence comparisons suggested that more than one fad2 gene is transcribed in maize embryos. Two different fad2 cDNAs from an embryo cDNA library map to separate chromosomal positions, providing evidence consistent with two different isoforms of fad2 expressed in the embryo. The fad2 cDNAs from multiple tissue sources clustered into three groups on a phenogram, and map to different positions on chromosomes 4, 5 and 10, which suggests at least three different isoforms of fad2 may be expressed in the maize plant. The two maize fad6 cDNAs share 81% amino-acid identity with the Arabidopsis fad6 and map to chromosome 1. Northern analysis revealed that fad2 is transcribed in embryos at 14, 21, 28 and 35 days after pollination, with the highest level observed at day 14. None of the fad2 or fad6 clones mapped to maize chromosome bins associated with QTLs for the ratio of oleic/linoleic acid, notably bin 6.04 which contains the linoleic1 locus and the largest reported QTL for the oleic/linoleic ratio. This suggests, but does not prove, that some of the QTLs for the oleic/linoleic acid ratio do not involve allelic variants of fad2 or fad6 but rather involve other genes that may influence flux through the enzymes encoded by fad2 or fad6.

DNA, Complementary↗
PubMed2003

Identification of AFLP markers linked to fertility restorer genes for tournefortii cytoplasmic male-sterility system in Brassica napus.

The tournefortii cytoplasmic male-sterility system is being used as a method of pollination control to develop hybrids in Brassica napus. Genetic analyses have indicated that two dominant genes, one major ( Rft1) and another minor ( Rft2), were required to achieve complete fertility restoration. Though the major gene ( Rft1) can cause complete fertility restoration on its own, its expression was significantly enhanced in the presence of the minor gene ( Rft2). In the absence of Rft1, Rft2 caused only partial fertility restoration. We used a pair of near-isogenic lines (NILs), differing for the presence/absence of Rf genes, to identify AFLP markers linked to fertility restorer genes. A total of 64 EcoRI/ MseI primer combinations were surveyed which produced 3,225 bands, of which 19 (0.006%) were polymorphic between parental NILs. Primer combinations which led to the identification of polymorphic bands present in fertile parental NILs were used for assaying a mapping population of 70 F(2) plants for determining the segregation pattern of markers. Initial screening resulted in the identification of five AFLP markers. The recombination analyses of these AFLP markers revealed that at least two (EACC/MCTT(105), EAAG/MCTC(80)) were present in the same linkage group along with the Rf loci. Marker EACC/MCTT(105) was separated from the major gene ( Rft1) by a distance of 18.1 cM, while it was 33.2 cM away from the minor fertility restorer gene ( Rft2). Another marker EAAG/MCTC(80) was also located adjacent to Rft1 at a distance of 18.1 cM, but on other side. Identification of flanking markers (EACC/MCTT(105), EAAG/MCTC(80)) for the major fertility restorer gene ( Rft1) provides a crucial component for marker-assisted selection and map-based cloning of the restorer genes, and can hence be used to construct elite restorer genotypes.

Brassica↗
PubMed2003

A PCR-based marker system monitoring CMS-(S), CMS-(T) and (N)-cytoplasm in the onion ( Allium cepa L.).

The chimerical mitochondrial CMS(1)-specific sequence in chives ( Allium schoenoprasum) was used to develop a PCR-marker that distinguishes both male-sterility inducing cytoplasms, CMS-(S) and CMS-(T), from the normal cytoplasm in onion ( Allium cepa). In combination with a previously described marker for CMS-(S), which anchors in the upstream region of the mitochondrial gene cob, all of the three known cytoplasms in the onion are distinguishable. The PCR-marker system was tested in 361 onion plants, which were selected from F(1)-hybrids and different open-pollinated varieties. The latter are mainly landraces from Turkey, in which all three cytoplasm types were detected.

Breeding↗
PubMed2003

An apricot (Prunus armeniaca L.) F2 progeny linkage map based on SSR and AFLP markers, mapping plum pox virus resistance and self-incompatibility traits.

A genetic linkage map of apricot ( Prunus armeniaca L.) was constructed using AFLP and SSR markers. The map is based on an F(2) population (76 individuals) derived from self-pollination of an F(1) individual ('Lito') originated from a cross between 'Stark Early Orange' and 'Tyrinthos'. This family, designated as 'Lito' x 'Lito', segregated for two important agronomical traits: plum pox virus resistance (PPV) and self-incompatibility. A total of 211 markers (180 AFLPs, 29 SSRs and two agronomic traits) were assigned to 11 linkage groups covering 602 cM of the apricot genome. The average distance (cM/marker) between adjacent markers is 3.84 cM. The PPV resistance trait was mapped on linkage group G1 and the self-incompatibility trait was mapped on linkage group G6. Twenty two loci held in common with other Prunus maps allowed us to compare and establish homologies among the respective linkage groups.

Breeding↗
PubMed2003

Characterisation of the phosphoenolpyruvate carboxylase gene family in sugarcane (Saccharum spp.).

Phosphoenolpyruvate carboxylases (PEPCs) are encoded by a small multigenic family. In order to characterise this gene family in sugarcane, seven DNA fragments displaying a high homology with grass PEPC genes were isolated using polymerase chain reaction-based cloning. A phylogenetic study revealed the existence of four main PEPC gene lineages in grasses and particularly in sugarcane. Moreover, this analysis suggests that grass C4 PEPC has likely derived from a root pre-existing isoform in an ancestral species. Using the Northern-dot-blot method, we studied the expression of the four PEPC gene classes in sugarcane cv. R570. We confirmed that transcript accumulation of the C4 PEPC gene (ppc-C4) mainly occurs in the green leaves and is light-induced. We also showed that another member of this gene family (ppc-aR) is more highly transcribed in the roots. The constitutive expression for a previously characterised gene (ppc-aL2) was confirmed. Lastly, the transcript accumulation of the fourth PEPC gene class (ppc-aL1) was not revealed. Length polymorphism in non-coding regions for three PEPC gene lineages enabled us to develop sequence-tagged site PEPC markers in sugarcane. We analysed the segregation of PEPC fragments in self-pollinated progenies of cv. R570 and found co-segregating fragments for two PEPC gene lineages. This supports the hypothesis that diversification of the PEPC genes involved duplications, probably in tandem.

Base Sequence↗
PubMed2003

Genetic evaluation of alternative silvicultural systems in coastal montane forests: western hemlock and amabilis fir.

Genetic diversity and mating system were quantified for shelterwood, patch cut and green tree-retention silvicultural systems, and compared to adjacent old-growth. This is a component of a larger study conducted in montane old-growth forests of coastal British Columbia to evaluate the feasibility and ecological consequences of alternative silvicultural systems. The experiment includes replicated treatments representing a range of overstory removal adjacent to old-growth and clearcut areas. Based on 22 electrophoretically assayed loci, the effects of silvicultural systems on genetic parameters of amabilis fir (Abies amabilis and western hemlock (Tsuga heterophylla were assessed by comparing an average number of alleles per locus, the percent polymorphic loci, and observed and expected heterozygosity between parental populations and naturally regenerated progeny as well as among treatments. Genetic variation in natural regeneration was greater than in parental populations, especially for low-frequency alleles. Silvicultural treatments caused no significant differences in amabilis fir genetic-diversity parameters, while the shelterwood system resulted in lower observed and expected heterozygosity in western hemlock. Nei's genetic distance revealed that all parental populations were extremely similar. The two species had contrasting mating system dynamics with amabilis fir producing higher levels of correlated paternity and inbreeding with wider variation among individual tree outcrossing-rate estimates. Western hemlock had significant levels of correlated paternity only for the green tree and shelterwood treatments demonstrating family structuring inversely related to stand density. Inbreeding in western hemlock was significant but lower than that observed for amabilis fir with a J-shaped distribution for individual tree multilocus outcrossing-rate estimates. The pollination and dispersal mechanisms of the two species represent the most-likely factors causing these differences. Artificial regeneration may be utilized to augment the genetic resources of natural ingress.

Abies↗
PubMed2003

Transmission and recombination of homeologous Solanum sitiens chromosomes in tomato.

The goal of the present experiments was to transfer the chromosomes of Solanum sitiens (syn. Solanum rickii) into cultivated tomato ( Lycopersicon esculentum). By crossing an allotetraploid L. esculentum x Solanum sitiens hybrid to sesquidiploid L. esculentum x S. lycopersicoides, a trigenomic hybrid (2n+14=38) was obtained. Analysis of the latter by GISH (genomic in situ hybridization) indicated it contained a full set of 12 S. sitiens chromosomes, plus two extras from S. lycopersicoides. This and other complex hybrids were pollinated with Lycopersicon pennellii-derived bridging lines to overcome unilateral incompatibility. A total of 40 progeny were recovered by embryo rescue, including diploids and aneuploids (up to 2n+8). In order to determine the origin of chromosomes and the location of introgressed segments, progeny were genotyped with RFLP markers. S. sitiens-specific markers on all chromosomes, except 6 and 11, were detected in the progeny. Several S. sitiens chromosomes were transmitted intact, either through chromosome addition (i.e., trisomics) or substitution (i.e., disomics). Recombination between S. sitiens and L. esculentum was detected on most chromosomes, in both diploid and aneuploid progeny. A monosomic alien addition line for S. sitiens chromosome 8 was identified, and the extra chromosome was stably transmitted to approximately 13% of the backcross progeny. This study demonstrates the feasibility of gene transfer from S. sitiens to L. esculentum through chromosome addition, substitution, and recombination in the progeny of complex aneuploid hybrids.

Chromosomes, Plant↗
PubMed2003

Additive transgene expression and genetic introgression in multiple green-fluorescent protein transgenic crop x weed hybrid generations.

The level of transgene expression in crop x weed hybrids and the degree to which crop-specific genes are integrated into hybrid populations are important factors in assessing the potential ecological and agricultural risks of gene flow associated with genetic engineering. The average transgene zygosity and genetic structure of transgenic hybrid populations change with the progression of generations, and the green fluorescent protein (GFP) transgene is an ideal marker to quantify transgene expression in advancing populations. The homozygous T(1) single-locus insert GFP/ Bacillus thuringiensis (Bt) transgenic canola ( Brassica napus, cv Westar) with two copies of the transgene fluoresced twice as much as hemizygous individuals with only one copy of the transgene. These data indicate that the expression of the GFP gene was additive, and fluorescence could be used to determine zygosity status. Several hybrid generations (BC(1)F(1), BC(2)F(1)) were produced by backcrossing various GFP/Bt transgenic canola ( B. napus, cv Westar) and birdseed rape ( Brassica rapa) hybrid generations onto B. rapa. Intercrossed generations (BC(2)F(2) Bulk) were generated by crossing BC(2)F(1) individuals in the presence of a pollinating insect ( Musca domestica L.). The ploidy of plants in the BC(2)F(2) Bulk hybrid generation was identical to the weedy parental species, B. rapa. AFLP analysis was used to quantify the degree of B. napus introgression into multiple backcross hybrid generations with B. rapa. The F(1) hybrid generations contained 95-97% of the B. napus-specific AFLP markers, and each successive backcross generation demonstrated a reduction of markers resulting in the 15-29% presence in the BC(2)F(2) Bulk population. Average fluorescence of each successive hybrid generation was analyzed, and homozygous canola lines and hybrid populations that contained individuals homozygous for GFP (BC(2)F(2) Bulk) demonstrated significantly higher fluorescence than hemizygous hybrid generations (F(1), BC(1)F(1) and BC(2)F(1)). These data demonstrate that the formation of homozygous individuals within hybrid populations increases the average level of transgene expression as generations progress. This phenomenon must be considered in the development of risk-management strategies.

Crops, Agricultural↗
PubMed2003

Gene flow in cherry orchards.

A survey of Australian cherry orchards identified the cherry cultivars Sunburst, Summit, Merchant, Sam, Sylvia, Tieton, Kordia, Regina, Empress, Nordwunder and Ulster as having low fruit-set associated with poor pollination. Unique orchard sites across Australia where low fruit-set was not a problem for these cultivars were located, and pollen gene-flow-analysis conducted using 6-PGD, GOT, G6PD, GPI, IDH, FDP and SKDH isozyme markers. Pollenisers for the above-mentioned cultivars were determined and Stella was a polleniser for eight of them. Stella's predominance was linked to it reaching full bloom before the other cultivars; anther dehiscence occurs sometime after flowers open, as such newly opened flowers; the most-fertile stage was mainly exposed to Stella pollen. Sunburst a self-compatible cultivar showed no evidence of self-fertilisation. The majority of pollenisers were found to be within 20 m of the tree under examination. Isozyme profiles for 22 cultivars not previously analysed are also presented.

Agriculture↗