Rapid elimination of low-copy DNA sequences in polyploid wheat: a possible mechanism for differentiation of homoeologous chromosomes

To study genome evolution in allopolyploid plants, we analyzed polyploid wheats and their diploid progenitors for the occurrence of 16 low-copy chromosome- or genome-specific sequences isolated from hexaploid wheat. Based on their occurrence in the diploid species, we classified the sequences into two groups: group I, found in only one of the three diploid progenitors of hexaploid wheat, and group II, found in all three diploid progenitors. The absence of group II sequences from one genome of tetraploid wheat and from two genomes of hexaploid wheat indicates their specific elimination from these genomes at the polyploid level. Analysis of a newly synthesized amphiploid, having a genomic constitution analogous to that of hexaploid wheat, revealed a pattern of sequence elimination similar to the one found in hexaploid wheat. Apparently, speciation through allopolyploidy is accompanied by a rapid, nonrandom elimination of specific, low-copy, probably noncoding DNA sequences at the early stages of allopolyploidization, resulting in further divergence of homoeologous chromosomes (partially homologous chromosomes of different genomes carrying the same order of gene loci). We suggest that such genomic changes may provide the physical basis for the diploid-like meiotic behavior of polyploid wheat.

Plant domestication versus crop evolution: a conceptual framework for cereals and grain legumes

'Domestication syndrome' (DS) denotes differences between domesticated plants and their wild progenitors. Crop plants are dynamic entities; hence, not all parameters distinguishing wild progenitors from cultigens resulted from domestication. In this opinion article, we refine the DS concept using agronomic, genetic, and archaeobotanical considerations by distinguishing crucial domestication traits from traits that probably evolved post-domestication in Near Eastern grain crops. We propose that only traits showing a clear domesticated-wild dimorphism represent the pristine domestication episode, whereas traits showing a phenotypic continuum between wild and domesticated gene pools mostly reflect post-domestication diversification. We propose that our approach may apply to other crop types and examine its implications for discussing the timeframe of plant domestication and for modern plant science and breeding.

Rapid genomic changes in newly synthesized amphiploids of Triticum and Aegilops. I. Changes in low-copy noncoding DNA sequences

We recently reported that allopolyploid formation in wheat was accompanied by rapid nonrandom elimination of specific low-copy, noncoding DNA sequences. These sequences occur in all diploid progenitors but are chromosome- or genome-specific at the polyploid level. To further investigate this phenomenon, we studied nine of these sequences, six chromosome-specific sequences and three genome-specific sequences, all isolated from common wheat. The various sequences were hybridized to DNA derived from nine newly synthesized amphiploids at different ploidy levels and to DNA from their parental lines. Although sequences homologous to the probes occur in all parental lines, a nonrandom loss of hybridization fragments was found at a high frequency in all amphiploids studied. In addition, a "loss/gain" of a hybridization fragment(s) was noticed in some of the amphiploids at lower frequency. Neither the type nor the frequency of changes was affected by intergenomic recombination or DNA methylation. It is suggested that rapid genomic changes culminated in a "programmed" pattern of elimination and (or) modification of specific low-copy DNA sequences following allopolyploidization. These events augmented the differentiation of homoeologous chromosomes, thus providing the physical basis for the diploid-like cytological behavior of polyploid wheat.Key words: wheat, allopolyploidy, genome evolution, chromosome- or genome-specific sequences, sequence elimination, homoeologous chromosome differentiation.

Genomic dissection of drought resistance in durum wheat x wild emmer wheat recombinant inbreed line population

Drought is the major factor limiting wheat productivity worldwide. The gene pool of wild emmer wheat, Triticum turgidum ssp. dicoccoides, harbours a rich allelic repertoire for morpho-physiological traits conferring drought resistance. The genetic and physiological bases of drought responses were studied here in a tetraploid wheat population of 152 recombinant inbreed lines (RILs), derived from a cross between durum wheat (cv. Langdon) and wild emmer (acc# G18-16), under contrasting water availabilities. Wide genetic variation was found among RILs for all studied traits. A total of 110 quantitative trait loci (QTLs) were mapped for 11 traits, with LOD score range of 3.0-35.4. Several QTLs showed environmental specificity, accounting for productivity and related traits under water-limited (20 QTLs) or well-watered conditions (15 QTLs), and in terms of drought susceptibility index (22 QTLs). Major genomic regions controlling productivity and related traits were identified on chromosomes 2B, 4A, 5A and 7B. QTLs for productivity were associated with QTLs for drought-adaptive traits, suggesting the involvement of several strategies in wheat adaptation to drought stress. Fifteen pairs of QTLs for the same trait were mapped to seemingly homoeologous positions, reflecting synteny between the A and B genomes. The identified QTLs may facilitate the use of wild alleles for improvement of drought resistance in elite wheat cultivars.

Viewpoint: Evolution of cultivated chickpea: four bottlenecks limit diversity and constrain adaptation

Chickpea (Cicer arietinum L.) is characterised by a different adaptation profile from the other crops of West Asian origin such as pea, barley, and wheat. In this paper we suggest that a series of four evolutionary bottlenecks occur in chickpea: (1) the scarcity and limited distribution of the wild progenitor, C. reticulatum Ladiz., (2) the founder effect associated with domestication, (3) the shift, early in the crop's history, from winter to spring sowing, and the attendant change from using rainfall as it occurs to a reliance on residual soil moisture, and (4) the replacement of locally evolving landraces by elite cultivars produced by modern plant breeding. While two of the bottlenecks are common to all species, the limited distribution of the wild progenitor and shift of cropping from utilisation of current rainfall to stored soil moisture is unique to chickpea. In this paper we suggest that in order to widen the genetic base of cultivated chickpea it is imperative to reintroduce traits from across the primary gene pool. Moreover, a comparative physiological approach to the study of adaptation among the annual wild relatives of chickpea may reveal adaptive strategies within the genus currently obscured by monomorphic loci. The poor state of the world collection of annual wild Cicer species severely constrains the implementation of both these imperatives. We suggest that an extensive collection of annual wild Cicer species, based on ecogeographic principles to maximise the probability of collecting diverse ecotypes, should provide a better understanding of the biology and adaptation in this ancient crop and lead to improved productivity.

Genetic analysis of wheat domestication and evolution under domestication

Wheat is undoubtedly one of the world's major food sources since the dawn of Near Eastern agriculture and up to the present day. Morphological, physiological, and genetic modifications involved in domestication and subsequent evolution under domestication were investigated in a tetraploid recombinant inbred line population, derived from a cross between durum wheat and its immediate progenitor wild emmer wheat. Experimental data were used to test previous assumptions regarding a protracted domestication process. The brittle rachis (Br) spike, thought to be a primary characteristic of domestication, was mapped to chromosome 2A as a single gene, suggesting, in light of previously reported Br loci (homoeologous group 3), a complex genetic model involved in spike brittleness. Twenty-seven quantitative trait loci (QTLs) conferring threshability and yield components (kernel size and number of kernels per spike) were mapped. The large number of QTLs detected in this and other studies suggests that following domestication, wheat evolutionary processes involved many genomic changes. The Br gene did not show either genetic (co-localization with QTLs) or phenotypic association with threshability or yield components, suggesting independence of the respective loci. It is argued here that changes in spike threshability and agronomic traits (e.g. yield and its components) are the outcome of plant evolution under domestication, rather than the result of a protracted domestication process. Revealing the genomic basis of wheat domestication and evolution under domestication, and clarifying their inter-relationships, will improve our understanding of wheat biology and contribute to further crop improvement.

Key features of cereal genome organization as revealed by the use of cytosine methylation-sensitive restriction endonucleases

Unlike mammalian genomes, cereal (Gramineae) genomes exhibit little suppression of CpG dinucleotides. In cereal genomes, however, most of the numerous potential recognition sites for CpG methylation-sensitive restriction enzymes are methylated. Analysis of cereal genomic libraries and of regions flanking genes indicates that unmethylated NotI sites are useful landmarks for regions containing genes/single-copy sequences. Studies of a rye chromosome arm indicate that its pericentromeric region has a reduced density of unmethylated NotI (and MluI) sites and therefore of genes. Unmethylated MluI and NruI sites are distributed nonrandomly in the genomes of wheat, barley, and rice. Analysis of the genomic blocks defined by these sites in wheat and barley indicates that they are most likely to have arisen by amplification. These observations form the basis of a proposed model for the organization and evolution of the wheat, barley, and rice genomes.

Quantitative trait loci governing carotenoid concentration and weight in seeds of chickpea (Cicer arietinum L.)

Chickpea is a staple protein source in many Asian and Middle Eastern countries. The seeds contain carotenoids such as beta-carotene, cryptoxanthin, lutein and zeaxanthin in amounts above the engineered beta-carotene-containing "golden rice" level. Thus, breeding for high carotenoid concentration in seeds is of nutritional, socio-economic, and economic importance. To study the genetics governing seed carotenoids in chickpea, we studied the relationship between seed weight and concentrations of beta-carotene and lutein by means of high-performance liquid chromatography in segregating progeny from a cross between an Israeli cultivar and wild Cicer reticulatum Ladiz. Seeds of the cross progeny varied with respect to their carotenoid concentration (heritability estimates ranged from 0.5 to 0.9), and a negative genetic correlation was found between mean seed weight and carotenoid concentration in the F(3). To determine the loci responsible for the genetic variation observed, the population was genotyped using 91 sequence tagged microsatellite site markers and two CytP450 markers to generate a genetic map consisting of nine linkage groups and a total length of 344.6 cM. Using quantitative data collected for beta-carotene and lutein concentration and seed weight of the seeds of the F(2) population, we were able to identify quantitative trait loci (QTLs) by interval mapping. At a LOD score of 2, four QTLs for beta-carotene concentration, a single QTL for lutein concentration and three QTLs for seed weight were detected. The results of this investigation may assist in improving the nutritional quality of chickpea.

Mapping quantitative trait loci in chickpea associated with time to flowering and resistance to Didymella rabiei the causal agent of Ascochyta blight

Drought is the major constraint to chickpea (Cicer arietinum L.) productivity worldwide. Utilizing early-flowering genotypes and advancing sowing from spring to autumn have been suggested as strategies for drought avoidance. However, Ascochyta blight (causal agent: Didymella rabiei (Kov.) v. Arx.) is a major limitation for chickpea winter cultivation. Most efforts to introgress resistance to the pathogen into Kabuli germplasm resulted in relatively late flowering germplasm. With the aim to explore the feasibility of combining earliness and resistance, RILs derived from a cross between a Kabuli cultivar and a Desi accession were evaluated under field conditions and genotyped with SSR markers. Three quantitative trait loci (QTLs) with significant effects on resistance were identified: two linked loci located on LG4 in epistatic interaction and a third locus on LG8. Two QTLs were detected for time to flowering: one in LG1 and another on LG2. When resistance and time to flowering were analyzed together, the significance of the resistance estimates obtained for the LG8 locus increased and the locus effect on days to flowering, previously undetected, was significantly different from zero. The identification of a locus linked both to resistance and time to flowering may account for the correlation observed between these traits in this and other breeding attempts.

Construction of BAC and BIBAC libraries and their applications for generation of SSR markers for genome analysis of chickpea, Cicer arietinum L

Large-insert bacterial artificial chromosome (BAC) libraries, plant-transformation-competent binary BAC (BIBAC) libraries, and simple sequence repeat (SSR) markers are essential for many aspects of genomics research. We constructed a BAC library and a BIBAC library from the nuclear DNA of chickpea, Cicer arietinum L., cv. Hadas, partially digested with HindIII and BamHI, respectively. The BAC library has 14,976 clones, with an average insert size of 121 kb, and the BIBAC library consists of 23,040 clones, with an average insert size of 145 kb. The combined libraries collectively cover ca. 7.0 x genomes of chickpea. We screened the BAC library with eight synthetic SSR oligos, (GA)10, (GAA)7, (AT)10, (TAA)7, (TGA)7, (CA)10, (CAA)7, and (CCA)7. Positive BACs were selected, subcloned, and sequenced for SSR marker development. Two hundred and thirty-three new chickpea SSR markers were developed and characterized by PCR, using chickpea DNA as template. These results have demonstrated that BACs are an excellent source for SSR marker development in chickpea. We also estimated the distribution of the SSR loci in the chickpea genome. The SSR motifs (TAA)n and (GA)n were much more abundant than the others, and the distribution of the SSR loci appeared non-random. The BAC and BIBAC libraries and new SSR markers will provide valuable resources for chickpea genomics research and breeding (the libraries and their filters are available to the public at http://hbz.tamu.edu).

The Chickpea, Summer Cropping, and a New Model for Pulse Domestication in the Ancient Near East

The widely accepted models describing the emergence of domesticated grain crops from their wild type ancestors are mostly based upon selection (conscious or unconscious) of major features related either to seed dispersal (nonbrittle ear, indehiscent pod) or free germination (nondormant seeds, soft seed coat). Based on the breeding systems (self-pollination) and dominance relations between the allelomorphs of seed dispersal mode and seed dormancy, it was postulated that establishment of the domesticated forms and replacement of the wild ancestral populations occurred in the Near East within a relatively short time. Chickpea (Cicer arietinum L.), however, appears as an exception among all other "founder crops" of Old World agriculture because of its ancient conversion into a summer crop. The chickpea is also exceptional because its major domestication trait appears to be vernalization insensitivity rather than pod indehiscence or free germination. Moreover, the genetic basis of vernalization response in wild chickpea (Cicer reticulatum Ladiz.) is polygenic, suggesting that a long domestication process was imperative due to the elusive phenotype of vernalization nonresponsiveness. There is also a gap in chickpea remains in the archaeological record between the Late Prepottery Neolithic and the Early Bronze Age. Contrary to the common view that Levantine summer cropping was introduced relatively late (Early Bronze Age), we argue for an earlier (Neolithic) Levantine origin of summer cropping because chickpea, when grown as a common winter crop, was vulnerable to the devastating pathogen Didymella rabiei, the causal agent of Ascochyta blight. The ancient (Neolithic) conversion of chickpea into a summer crop required seasonal differentiation of agronomic operation from the early phases of the Neolithic revolution. This topic is difficult to deal with, as direct data on seasonality in prehistoric Old World field crop husbandry are practically nonexistent. Consequently, this issue was hardly dealt with in the literature. Information on the seasonality of ancient (Neolithic, Chalcolithic, and Early Bronze Age, calibrated 11,500 to 4,500 years before present) Near Eastern agriculture may improve our understanding of the proficiency of early farmers. This in turn may provide a better insight into Neolithic agrotechniques and scheduling. It is difficult to fully understand chickpea domestication without a Neolithic seasonal differentiation of agronomic practice because the rapid establishment of the successful Near Eastern crop package which included wheats, barley, pea, lentil, vetches, and flax, would have preempted the later domestication of this rare wild legume.

Characterization of the calmodulin gene family in wheat: structure, chromosomal location, and evolutionary aspects

Calmodulin is a ubiquitous transducer of calcium signals in eukaryotes. In diploid plant species, several isoforms of calmodulin have been described. Here, we report on the isolation and characterization of calmodulin cDNAs corresponding to 10 genes from hexaploid (bread) wheat (Triticum aestivum). These genes encode three distinct calmodulin isoforms; one isoform is novel in that it lacks a conserved calcium binding site. Based on their nucleotide sequences, the 10 cDNAs were classified into four subfamilies. Using subfamily-specific DNA probes, calmodulin genes were identified and the chromosomal location of each subfamily was determined by Southern analysis of selected aneuploid lines. The data suggest that hexaploid wheat possesses at least 13 calmodulin-related genes. Subfamilies 1 and 2 were both localized to the short arms of homoeologous-group 3 chromosomes; subfamily 2 is located on all three homoeologous short arms (3AS, 3BS and 3DS), whereas subfamily 1 is located only on 3AS and 3BS but not on 3DS. Further analysis revealed that Aegilops tauschii, the presumed diploid donor of the D-genome of hexaploid wheat, lacks a subfamily-1 calmodulin gene homologue, whereas diploid species related to the progenitors of the A and B genomes do contain such genes. Subfamily 3 was localized to the short arm of homoeologous chromosomes 2A, 2B and 2D, and subfamily 4 was mapped to the proximal regions of 4AS, 4BL and 4DL. These findings suggest that the calmodulin genes within each subfamily in hexaploid wheat represent homoeoallelic loci. Furthermore, they also suggest that calmodulin genes diversified into subfamilies before speciation of Triticum and Aegilops diploid species.

Ecological genetic divergence of the fungal pathogen Didymella rabiei on sympatric wild and domesticated Cicer spp. (Chickpea)

For millennia, chickpea (Cicer arietinum) has been grown in the Levant sympatrically with wild Cicer species. Chickpea is traditionally spring-sown, while its wild relatives germinate in the autumn and develop in the winter. It has been hypothesized that the human-directed shift of domesticated chickpea to summer production was an attempt to escape the devastating Ascochyta disease caused by Didymella rabiei. We estimated genetic divergence between D. rabiei isolates sampled from wild Cicer judaicum and domesticated C. arietinum and the potential role of temperature adaptation in this divergence. Neutral genetic markers showed strong differentiation between pathogen samples from the two hosts. Isolates from domesticated chickpea demonstrated increased adaptation to higher temperatures when grown in vitro compared with isolates from the wild host. The distribution of temperature responses among progeny from crosses of isolates from C. judaicum with isolates from C. arietinum was continuous, suggesting polygenic control of this trait. In vivo inoculations of host plants indicated that pathogenic fitness of the native isolates was higher than that of their hybrid progeny. The results indicate that there is a potential for adaptation to higher temperatures; however, the chances for formation of hybrids which are capable of parasitizing both hosts over a broad temperature range are low. We hypothesize that this pathogenic fitness cost is due to breakdown of coadapted gene complexes controlling pathogenic fitness on each host and may be responsible for maintenance of genetic differentiation between the pathogen demes.

Chromosome painting in plants: in situ hybridization with a DNA probe from a specific microdissected chromosome arm of common wheat

We report here on the successful painting of a specific plant chromosome within its own genome. Isochromosomes for the long arm of chromosome 5 of the wheat B genome (5BL) were microdissected from first meiotic metaphase spreads of a monoisosomic 5BL line of the common wheat Triticum aestivum cv. Chinese Spring. The dissected isochromosomes were amplified by degenerate oligonucleotide-primed PCR in a single tube reaction. The amplified DNA was used as a complex probe mixture for fluorescent in situ hybridization on first meiotic metaphase spreads of lines carrying 5BL as a distinctive marker. Hybridization signals were observed, specifically, along the entire 5BL. In some of the cells, labeling was also detected in two bivalents, presumably those of the 5B "homoeologues" (partial homologues) found in common wheat (5A and 5D). The probe also revealed discrete domains in tapetal nuclei at interphase, further supporting the probe's high specificity. These data suggest that chromosome and homoeologous group-specific sequences are more abundant in 5BL than genome-specific sequences. Chromosome-painting probes, such as the one described here for 5BL, can facilitate the study of chromosome evolution in polyploid wheat.

The potential use of chickpeas in development of infant follow-on formula

BACKGROUND

Undernutrition during childhood is a common disorder in the developing countries, however most research has focussed much on its treatment rather than its prevention.

OBJECTIVE

We investigated the potential of using chickpeas in infant follow-on formula production against the requirements of WHO/FAO on complementary foods and EU regulations on follow-on formula.

METHODS

Chickpeas were germinated for 72 hours followed by boiling, drying and dehulling in order to minimise associated anti-nutrition factors. Saccharifying enzymes were used to hydrolyse starch to maltose and the resulting flours were analysed for their protein content and amino acid profile.

RESULTS

The protein content (percentage) increased from 16.66 ± 0.35 and 20.24 ± 0.50 to 20.00 ± 0.15 and 21.98 ± 0.80 for the processed desi and kabuli cultivar compared to raw chickpeas, respectively (P < 0.05). There was insignificant change (P = 0.05) in amino acid profile following processing and the resulting flour was found to meet the amino acid requirements of WHO/FAO protein reference for 0-24 month's children.

CONCLUSION

The designed chickpea based infant follow-on formula meets the WHO/FAO requirements on complementary foods and also the EU regulations on follow-on formula with minimal addition of oils, minerals and vitamins. It uses chickpea as a common source of carbohydrate and protein hence making it more economical and affordable for the developing countries without compromising the nutrition quality.

Detection of ribosomal DNA sites in lentil and chickpea by fluorescent in situ hybridization

Hybridization sites of an rDNA probe coding for the 18S, 5.8S, and 26S genes were detected on lentil and chickpea somatic chromosomes using fluorescent in situ hybridization. One pair of hybridization sites was detected in cultivated lentil Lens culinaris L. and wild lentil L. orientalis (Boiss.) Hand.-Mazz., and in both the hybridization sites of the ribosomal probe correspond to the secondary constriction. In cultivated chickpea Cicer arietinum three pairs of rDNA sites were detected and in the wild C. reticulatum two pairs were detected. The karyotypic relationship between the cultivated C. arietinum and its wild progenitor C. reticulatum is discussed.

Experimental growing of wild pea in Israel and its bearing on Near Eastern plant domestication

BACKGROUND AND AIMS

The wild progenitors of the Near Eastern legumes have low germination rates mediated by hardseededness. Hence it was argued that cultivation of these wild legumes would probably result in no yield gain. Based on the meagre natural yield of wild lentil and its poor germination, it was suggested that wild Near Eastern grain legumes were unlikely to have been adopted for cultivation unless freely germinating types were available for the incipient farmers. Unlike wild cereals, data from experimental cultivation of wild legumes are lacking.

METHODS

Replicated nurseries of wild pea (Pisum elatius, P. humile and P. fulvum) were sown during 2007-2010 in the Mediterranean district of Israel. To assess the effect of hardseededness on the yield potential, seeds of the wild species were either subjected to scarification (to ensure germination) or left intact, and compared with domesticated controls.

KEY RESULTS

Sowing intact wild pea seeds mostly resulted in net yield loss due to poor establishment caused by wild-type low germination rates, while ensuring crop establishment by scarification resulted in net, although modest, yield gain, despite considerable losses due to pod dehiscence. Harvest efficiency of the wild pea plots was significantly higher (2-5 kg seeds h(-1)) compared with foraging efficiency in wild pea populations (ranging from a few grams to 0·6 kg h(-1)).

CONCLUSIONS

Germination and yield data from 'cultivation' of wild pea suggest that Near Eastern legumes are unlikely to have been domesticated via a protracted process. Put differently, the agronomic implications of the hardseededness of wild legumes are incompatible with a millennia-long scenario of unconscious selection processes leading to 'full' domestication. This is because net yield loss in cultivation attempts is most likely to have resulted in abandonment of the respective species within a short time frame, rather than perpetual unprofitable cultivation for several centuries or millennia.

Osmotic adjustment in chickpea (Cicer arietinum L.) results in no yield benefit under terminal drought

Variation in osmotic adjustment (OA) among chickpea (Cicer arietinum L.) cultivars has been observed when exposed to terminal drought, but some studies suggest that this benefits yield while others suggest it does not benefit yield in water-limited environments. In the present study, parents differing in OA were crossed and a set of advanced breeding lines (ABLs) developed for yield testing. The variation in OA during podding was measured under terminal drought in the F(2), F(3), F(7), and F(8) progeny and in the parents by either rehydrating the leaves before sampling for osmotic potential (OP) or by measuring the relative water content (RWC) and OP on adjacent leaves for the calculation of the OP at full turgor. Yields were measured in the F(8) progeny under terminal drought in Australia and India. While differences in OA were measured in the chickpea lines and parents, OA varied from year to year and did not consistently benefit yield when measured in the field under terminal drought. In Australia, differences in OA were not associated with any yield benefit in any year, while in India early flowering resulted in higher yields at three of the four sites, and OA had an inconsistent effect on seed yields. A comparison of OP at full turgor measured after rehydration and from measurements of RWC and OP showed that the rehydration technique underestimated OA. The lack of contribution of OA to yield of chickpea is discussed.

Cytogenetics of semi-fertile triploid and aneuploid intergeneric vine cacti hybrids

Crosses between the diploid Hylocereus polyrhizus, as the female parent, and the tetraploid Selenicereus megalanthus, as the male parent, yielded triploid and aneuploid hybrids. The fruits of these hybrids combined the attractive appearance of Hylocereus fruits with the delicious taste of S. megalanthus fruits. The aim of this work was to assess the fertility and breeding potential of the triploid and aneuploid hybrids with a view to developing an improved vine cactus crop. Pollen mother cells at metaphase I revealed univalents, bivalents, trivalents, and occasionally quadrivalents. Chromosome distribution at anaphase I revealed different classes of chromosome segregation as well as lagging chromosomes. At metaphase II, parallel and tripolar spindles were observed. The occurrence of triads was frequent, whereas dyads were rarely observed. Pollen stainability varied among the clones studied ranging from 9.8% to 18.6%. The diameters of the stained pollen grains varied widely, probably as a result of the number of chromosomes. Despite the allotriploid origin of our hybrids, functional female and male gametes were produced in considerable proportions, most likely as a result of balanced chromosome segregation. The triploid and aneuploid clones studied yielded viable seeds whose number per fruit was strongly dependent on the pollen donor.