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Introduction. The diagnosis of SARS-CoV-2 infection is crucial for medical and public health reasons, to allow the best treatment of cases and the best control of the pandemic. Serology testing allows for the detection of asymptomatic infections and 19-COVID cases once the virus has been cleared. We analyzed the usefulness of the SARS-CoV-2 rapid test of Autobio and tried to correlate its pattern with the severity of COVID19 infection. Material and methods. We analyzed the accuracy and clinical usefulness of a point-of-care IgM and/or IgG test for SARS-CoV-2 in 35 COVID-19 patients [12 (34.3%) mild-moderate and 23 (65.7%) severe-critical] admitted to a field hospital in Madrid, as well as in 5 controls. Results. The mean time from the first day of symptoms to the antibody test was 28 days (SD: 8.7), similar according to the severity of the disease. All patients with SARS-CoV-2 PCR+ showed the corresponding IgG positivity, while these results were negative in all control individuals. A total of 26 (74%) cases also presented with positive IgM, 19 (83%) were severe-critical cases and 7 (58%) were mild-moderate cases. The IgM response lasted longer in the severe critical cases (mean: 29.7 days; SD: 8.4) compared to the moderate cases (mean: 21.2 days; SD: 2.0). Conclusions. Rapid serology tests are useful for the diagnosis of patients with COVID-19 (mainly IgG detection) and may also be correlated with the severity of the infection (based on IgM detection).

In this work, the origin of micronuclei production as well as microsporogenesis in Agave tequilana Weber cultivar “Azul” and A. angustifolia Haw. cultivar “Lineno” was studied. Both species showed ...

Sprekelia formosissima (L.) Herbert is a bulbous ornamental species of the Amaryllidaceae family, distributed from northern Mexico to Guatemala. Different reports on cytogenetic research on this species show differences in chromosome numbers (2n = 60, 120, 150, 180) with a basic number of x = 30. Since the chromosome number of plants can provide useful information for various fields of research including karyotaxonomy, genetics, and cytogenetics, it is important to determine the chromosome number for this species. Bulbs of S. formosissima were collected in three different locations in the state of Jalisco, Mexico. Meristematic root cells were analyzed cytogenetically using a modified steam-drop method. The three populations showed different chromosome numbers and ploidy levels, 2n = 2x = 60, 2n = 4x = 120, and 2n = 5x = 150. The ploidy level was compared with morphological traits showing higher values related to higher ploidy levels. The populations analyzed correspond to new polyploid cytotypes of S. formosissima.

The development of novel ornamental cultivars requires phenotypic and genetic variation. Interspecific hybridization is an important tool to achieve this variation. Eustoma grandiflorum (Raf.) Shinner, commonly known as lisianthus, has gained importance among ornamental crops, as cut-flower or potted plant, due to the shape of its flowers, which after several years of breeding resembles those of the rose; however, the color of lisianthus flowers ranges from white to purple, including greenish, rose and blue, and many forms with colored eyes, rings and brushes. The genus is endemic to America, and it distributes from the southern United States to Central America, including the Caribbean islands. E. grandiflorum is restricted to the southern United States and to northern Mexico. E. exaltatum (L.) Salisb. Ex G. Don distributes from central Mexico to Central America. Lisianthus breeding began around 50 years ago, and due to an indirect selection, many of the available cultivars nowadays, are susceptible to high temperatures, and if the plantlets are exposed to temperatures above 25°C they might rosette. In this respect, in order to achieve genetic variation and produce heat tolerant Eustoma cultivars, we conducted a breeding program, which includes interspecific hybridization among E. grandiflorum and E. exaltatum, the last being found in its natural habitat at an average temperature above 25°C during summer. Many crosses were performed in both directions, and F1, BC1 and S1 generations were achieved, showing outstanding ornamental traits, such as different color patterns, stem and flower size and heat tolerance. Furthermore, chromosome counts and chromosome identification were possible through in situ hybridization of rDNA and retrotransposon probes to metaphasic chromosomes in both species.

Preparations that contain well-spread metaphase chromosomes are critical for plant cytogenetic analyses including chromosome counts, banding procedures, in situ hybridization, karyotyping and construction of ideograms. Chromosome spreading is difficult for plants with large and numerous chromosomes. We report here a technique for obtaining cytoplasm-free, well-spread metaphases from two Amaryllidaceae species: Sprekelia formosissima (2n = 120) and Hymenocallis howardii (2n = 96). The technique has three main steps: 1) pretreatment to cause chromosome condensation, 2) dripping onto tilted slides coated with a thin layer of pure acetic acid and 3) application of steam and acetic acid to produce cytoplasmic hydrolysis, which spreads the chromosomes.

This study is a cytogenetic characterization by karyotyping and determination of the DNA content by flow cytometry of Agave angustifolia Haw. “Cimarron” and “Lineno” that were collected in the sout...

Dioscorea sparsiflora Hemsley (camote de cerro) is a wild species with agricultural potential that is not exploited as a crop but is collected for consumption and sale in western Mexico. The objective of the present research was to evaluate the effect of different light intensities (26,000, 18,000, and 14,000 lux), three shading periods (60, 90, and 180 d), and five types of containers two cylindrical (7 and 9 L), one rectangular (60 L), and two hydroponic channels: one 30 cm wide (45 L), and the other, 40 cm wide (60 L) on two D. sparsiflora accessions. The performances of two accessions (751 and 112) in previous treatments were also evaluated. The tuber weight was highest, with 18,000 lux (6.9 t ha–¹), and had the highest yield when cultivated with a 60 d shading (33 t ha–¹) and in the rectangular container (40 t ha–¹). Accession 751 obtained the highest averages for tuber weight and diameter (43 t ha–¹ and 73 mm, respectively).

Tuberose is an ornamental plant of economic importance produced worldwide due to the elegant shape and fragrant flowers. Despite its commercial importance, one of the limitations of tuberose production is control of flowering time, which has not been determined at present. In our research, the flowering time has been evaluated in corms of Agave amica cv. Double, during two production cycles (2017 and 2018) using different times of storage of the corms (4, 5, 6 and 7 weeks) at variable temperatures (4 °C, 12 °C, 27 °C, RT). Also, we studied the development of the corms to determine which changes occur in the meristem during floral transition and how the flower quality is affected. The results showed that meristematic differentiation occurred 30-45 days after establishment (DAE) in both culture cycles, although there was no temperature treatment that clearly affected the meristem growth. However, some floral characters were affected, the earliest sprouting occurred in the treatment of six and seven weeks of storage at 27 °C at 20 DAE in 2017 and 10 DAE in 2018, respectively. In addition, the shortest time to flowering occurred in the treatment of seven weeks of storage at 27 °C at 79 days in 2017 and at 100.6 days in 2018, a value that is 30 days earlier than that obtained with the treatments of six weeks of storage at 12 °C, which delayed meristem transition, sprouting and flowering time. In contrast, treatments at 4 °C and GA3 were not statically different from the control in both years.

This study aimed to evaluate the genetic difference between 43 F1 hybrids and 8 parents, seven of Iris germanica and one of I. spuria and to estimate genetic parameters by using 10 descriptors and the morphological variation to determine their potential for genetic improvement. The mean comparisons showed that the Iris hybrids 10 and 11 had higher flower size than other Iris hybrids and the parental, a coveted trait that could be used in breeding programs, with the aim of increase sales. The Iris hybrid 8 showed the most significantly difference in crown diameter, flower branches diameter and flower peduncle diameter. The cluster of largely are could separation hybrids in terms of morphological characteristics. Irises a trait correlation with other traits makes possible indirect measurement. Relatively high heritability values, in broad sense, were found 97% for height plant, fall width and length, flower size and leaf width. These characters may be applied as useful traits in Iris breeding and for selection hybrids.

This study presents the cytogenetic characterization by karyotyping and a determination of the DNA content by flow cytometry of wild adult plants, plants grown from seeds of wild plants and bulbils of Agave parviflora subsp. flexiflora from Bacadehuachi to Nacori Town, Sonora, Mexico. The analyzed plants were diploids (2n = 2x = 60) and had three different structural cytotypes. The cytotype observed in wild adult plants was 44m + 4sm + 10st + 2t, the cytotype found in plants grown from seeds was 48m + 8st + 4t and the cytotype displayed by bulbils was 44m + 2sm + 14st. Agave parviflora subsp. flexiflora showed a bimodal karyotype of 10 large + 50 small chromosomes. All diploid plants had a secondary constriction in one pair of the large chromosomes. The arm ratio, the proportion of different types of large and small chromosomes, the mean of genome length and the asymmetry index of karyotypes clearly varied among all three diploid cytotypes. The pattern of variation among all the types of plants is probabl...

In horticulture, interspecific hybridization is one of the most important tools to achieve genetic variation; this is especially true when it comes to ornamental crops, where it is always necessary to introduce new traits, such as flower colour, petal shapes, stem size and strength, longevity, disease resistances and more. However, to maintain such traits in the progeny is necessary to introgress the genes of the alien species into the gene pool of the receptor species. To accomplish this, first sterility must be overcome, because, as a general rule, interspecific hybrids tend to be sterile. Mitotic polyploidization is a useful technique to come to such end, but the use of unreduced gametes is preferred because recombination occurs between the parental genomes and introgression might be achieved. Here it is described i) the production of interspecific, intersectional lily hybrids, obtained through the use special pollination techniques combined with ovary- and embryo-rescue techniques, in crosses of distantly related lily hybrids, cultivars and species from different taxonomical sections (L. longiflorum × Asiatic hybrids (LA), L. longiflorum × Oriental hybrids (LO), L. longiflorum × L. rubellum (LR), L. longiflorum × L. henryi (LH), L. henryi × L. candidum (HC), L. auratum × L. henryi (AuH), L. martagon × Asiatic hybrids (MA), Oriental hybrids × Asiatic hybrids (OA), Oriental hybrids × Trumpet hybrids (OT) and Oriental hybrids × L. pardalinum (OP)); ii) the use of molecular Genomic in situ Hybridization (GISH) to depict the mechanisms of 2n gamete formation and their use for the production of sexual polyploids; iii) the utilization of allotriploid BC1 progenies in introgression breeding and iv) the application of N2O to induce the formation of unreduced gametes in sterile lily hybrids.

Supercritical fluid extracts from flowers of Polianthes tuberosa var. double were ob tained using carbon dioxide as a solvent. Yield extract obtained was 2.5%. The effects of the pressure process (18 MPa, 28 MPa, and 38 MPa) and temperature process (313 K, 323 K, and 333 K) on the volatile composition of tuberose flowers extracts were evaluated, and a significant variation in chemical composition was found. Characteristic compounds of tuberose as methyl isoeugenol, benzyl benzoate, methyl anthranilate, pentacosene, and heptacosene were obtained mainly at 18 MPa and 333 K process conditions, and could be used in the perfume or fragrance industry. Components such as geraniol, farnesol, and methyl eugenol were also obtained, these extracts could be used in the development of cosmeceutical products. This work allowed to identification of the chemical composition profile and evaluation of the changes in tuberose extracts due to the extraction process.

Agave Linnaeus, 1753 is endemic of America and is considered one of the most important crops in Mexico due to its key role in the country’s economy. Cytogenetic analysis was carried out in A. tequilana Weber, 1902 ‘Azul’, A. cupreata Trelease et Berger, 1915 and A. angustifolia Haworth, 1812. The analysis showed that in all species the diploid chromosome number was 2n = 60, with bimodal karyotypes composed of five pairs of large chromosomes and 25 pairs of small chromosomes. Furthermore, different karyotypical formulae as well as a secondary constriction in a large chromosome pair were found in all species. Fluorescent in situ hybridization (FISH) was used for physical mapping of 5S and 18S ribosomal DNA (rDNA). All species analyzed showed that 5S rDNA was located in both arms of a small chromosome pair, while 18S rDNA was associated with the secondary constriction of a large chromosome pair. Data of FISH analysis provides new information about the position and number of rDNA loci and helps for detection of hybrids in breeding programs as well as evolutionary studies.

Single chromosome identification is of primal importance in the study of evolutive process in complex genomes, such as polyploidization and hybridization events, among others. Traditionally, chromosome identification is made by arranging the chromosomes by the length of the short (p) and the long (q) arms, identifying the centromeres and secondary constrictions. Furthermore, accurate chromosome identification can be performed trough chromosome differentiation techniques such as C-, N-, and Q-banding. In the last years, through the development of fluorescent in situ hybridization techniques (FISH), even more accurate single chromosome identification has been accomplished, by the hybridization of highly conserved repetitive sequences, such as rDNAs. However, particular probes must be developed through laborious isolation and cloning molecular techniques. The comparative genomic in situ hybridization (cGISH) is a straightforward technique that allows the identification of single chromosomes by the generation of signals of conserved DNA regions along the chromosomes of different species. In this study we labeled total genomic DNA of Triticum aestivum and Arabidopsis thaliana and hybridized it to chromosomes of different cultivars of the genus Lilium. Different stringencies were applied to determine the optimum removal of cross hybridization, the 80% stringency showed to be the best, giving a clear signal and removing most of the cross hybridization. Triticum aestivum total genomic DNA exhibited six landmarks on three homologous chromosomes in the three different cultivars while Arabidopsis thaliana total genomic DNA exhibited six landmarks on three homologous chromosomes of Lilium, one of these signals being in a different chromosome of those of the T. aestivum signals. Together with the DAPI bands the total genomic DNAs landmarks allowed the identification of six out of 12 single homologous chromosomes.

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.

For overcoming F1-sterility in interspecific hybrids, mitotic and meiotic polyploidisation is applied in lily and can result in fertile allopolyploids. The mechanism of viable pollen production of mitotic and meiotic polyploidisation is quite different. Mitotic polyploids are obtained by artificial chromosome doubling and results in normal pairing of homologous chromosome set, which enables the formation of 2x gametes during the meiosis. Meiotic polyploidisation, on the other hand, leads in rare cases of restitutional chromosome division, to the formation of unreduced gametes (2n gametes). In contrast to mitotic doubling, homoeologous recombination can occur in these gametes. Genomic in situ hybridization (GISH) was used to discriminate parental chromosomes in the F1 hybrids and backcross progenies to detect homoeologous recombination. Mitotic polyploidisation showed no homoeologous recombinations between the parental genomes whereas in meiotic polyploids it was detected in a high frequency. The use of 2n gametes is therefore the most promising approach for the introgression of desirable characters in using interspecific hybrids in breeding. In both cases, the frequency of viable gametes appeared to be low and limited to a few F1-hybrids. A new and promising method is developed in which 2n-gametes can be induced by the application of laughing gas (N2O). This method proved to be successful in lily and the occurrence of homoeologous recombination, a characteristic of meiotic polyploidisation, was detected. In tulip where the production of mitotic polyploids requires at least five years, it will speed up breeding with interspecific hybrids enormously

Eight different genotypes of the F1 hybrids between Oriental × Asiatic lily (Lilium) hybrids (2n = 2x = 24) were treated with nitrous oxide (N2O) gas under pressure for 24 and 48 hours. At the time of treatment, all plants possessed early meiotic stages in the anthers of the oldest flower buds. The mature flowers from treated plants were monitored for fertility through pollen germination in vitro as well as by using them in crosses with diploid Asiatic hybrids (2n = 2x = 24) both as male and female parents. In five out of the eight genotypes of OA hybrids there was evidence for the production of 2n pollen which germinated in vitro from either one or both treatments. The 2n pollen from three genotypes was successfully used in crosses. In two cases, the treated plants were successfully used as female parents which indicated the formation of 2n (or 2x) egg cells. From an analysis of 41 sexual polyploid progenies obtained from N2O treated plants it was shown that they were all euploids consisting of 34 triploids (2n = 3x = 36) and seven tetraploids (2n = 4x = 48). A detailed cytological analysis of 12 progeny plants through genomic in situ hybridization (GISH) proved that N2O had induced first division restitution gametes in most cases and in two cases they produced gametes through indeterminate meiotic restitution. There was evidence for intergenomic recombination in three cases.

It is attractive to use 2n gametes in breeding for three reasons: a) they can overcome the sterility of F1 hybrids between distantly related species, b) facilitate homoeologous recombination between alien chromosomes and c) generate a large number of different genotypes of 2n gametes from a single F1 hybrid. Such genetic variation can be potentially useful for breeding. However, there is one drawback of using 2n gametes in breeding. The frequency of 2n gamete-producing genotypes OA-hybrids, is very low. By producing a large number of interspecific hybrids followed by careful screening, we have selected few 2n gamete producing F1 hybrids between different groups of Lilium species. This screening for 2n pollen production revealed enormous variation in 2n pollen production frequencies between the different genotypes and between the same genotypes grown in different environments. The fluctuations in greenhouse temperature appeared to influence 2n gametes frequency considerably. To study this during several years, four normally complete sterile genotypes were exposed to a heat shock treatment in phytotron. Three out of the four genotypes produced viable 2n pollen. In total 2% of the treated flowers became fertile due to this temperature-induced stimulation of 2n pollen formation.

Cytological modes of the origin of 2n gametes were investigated in six different genotypes of F1 hybrids between Oriental and Asiatic (OA) lilies (Lilium, 2n = 2x = 24). Chromosome pairing between the parental genomes was very low, the average frequency range from 0.3 to 1.2 bivalents per cell among the genotypes. Within a genotype the frequency of bivalents varied from 0 to 6 in some cases. The normally occurring haploid pollen grains were totally sterile. In contrast, in different genotypes, variable percentages of 2n pollen were found and shown to be fertile as estimated from pollen germination. A cytological analysis of Metaphase I and subsequent stages of meiosis using genomic in situ hybridization (GISH) revealed that there was intergenomic recombination between the alien genomes. Following Metaphase I stage, three different types of abnormal cytological events led to the formation of 2n pollen: (i) Post-Metaphase I division (PMI), (ii) Post-Metaphase II division (PMII) and (iii) Asymmetric Cytokinesis of the pollen mother cell followed by chromosome division. All three cytological events led to first division restitution (FDR) gametes. Based on in vitro pollen germination it was proved for two genotypes that 2n pollen was viable only during the first day of anthesis. It was possible to use 2n pollen successfully for backcrossing. Implications of 2n pollen for intergenomic recombination in BC1 progenies are discussed.

Genetic recombination is an important pre-requisite for transferring specific genetic traits across distantly related plant species. With a view to transfer some of the desirable characters like resistances against viruses, Fusarium and Botrytis, besides many horticultural traits, we have made interspecific hybrids between different species of lilies (Lilium, 2n=2x=24). The F1 hybrids in all these cases are totally sterile because of the lack of chromosome pairing. Traditional method of somatic chromosome doubling (mitotic polyploidization) can produce fertile allotetraploids. But, because of strict autosyndetic pairing in allotetraploids, no genetic recombination occurs in the progenies. In order to overcome this difficulty, we have selected 2n gamete producing F1 hybrids of different Lilium species and used them successfully for sexual polyploidization (meiotic polyploidization). An important feature of meiosis in the F1 hybrids is that a certain amount of homoeologous chromosome pairing does occur in them. When 2n gametes originate from such F1 hybrids through first division restitution (FDR) they are expected to possess recombinant chromosomes. Cytological analyses, using genomic in situ hybridization (GISH), of the sexual polyploid progenies have proved that considerable amount of intergenomic recombinant chromosomes can be recovered in the chromosome complements. One example of the sexual polyploid progenies from Oriental x Asiatic hybrid lilies possessing intergenomic recombinant chromosomes will be illustrated and discussed.

Background Individuals with factor V Leiden or prothrombin G20210A mutations are at a higher risk to develop venous thromboembolism. However, the influence of these polymorphisms on patient outcome during anticoagulant therapy has not been consistently explored. Methods We used the Registro Informatizado de Enfermedad TromboEmbolica database to compare rates of venous thromboembolism recurrence and bleeding events occurring during the anticoagulation course in factor V Leiden carriers, prothrombin mutation carriers, and noncarriers. Results Between March 2001 and December 2015, 10,139 patients underwent thrombophilia testing. Of these, 1384 were factor V Leiden carriers, 1115 were prothrombin mutation carriers, and 7640 were noncarriers. During the anticoagulation course, 160 patients developed recurrent deep vein thrombosis and 94 patients developed pulmonary embolism (16 died); 154 patients had major bleeding (10 died), and 291 patients had nonmajor bleeding. On multivariable analysis, factor V Leiden carriers had a similar rate of venous thromboembolism recurrence (adjusted hazard ratio [HR], 1.16; 95% confidence interval [CI], 0.82-1.64), half the rate of major bleeding (adjusted HR, 0.50; 95% CI, 0.25-0.99) and a nonsignificantly lower rate of nonmajor bleeding (adjusted HR, 0.66; 95% CI, 0.43-1.01) than noncarriers. Prothrombin mutation carriers and noncarriers had a comparable rate of venous thromboembolism recurrence (adjusted HR, 1.00; 95% CI, 0.68-1.48), major bleeding (adjusted HR, 0.75; 95% CI, 0.42-1.34), and nonmajor bleeding events (adjusted HR, 1.10; 95% CI, 0.77-1.57). Conclusions During the anticoagulation course, factor V Leiden carriers had a similar risk for venous thromboembolism recurrence and half the risk for major bleeding compared with noncarriers. This finding may contribute to decision-making regarding anticoagulation duration in selected factor V Leiden carriers with venous thromboembolism.

A cytological analysis of the microsporogenesis was carried out in the Agave tequilana and A. angustifolia species. Several abnormalities such as chromosomal bridges, lagging chromosomes, micronuclei, monads, dyads and triads were found. The morphological analysis of the pollen, together with the above-mentioned 2n microspores, allowed us to confirm the presence of 2n pollen as well as its frequency. In both A. tequilana and A. angustifolia two different mechanisms were observed: the first mechanism, a failure in the cytokinesis in meiosis II caused the formation of dyads with two 2n cells and triads containing two n cells and one 2n cell; the second mechanism, involves an abnormal spindle, which caused the formation of triads with two n cells and one 2n cell. Likewise, the presence of monads was detected in both species, these, might be caused by a failure of the cytokinesis in both meiotic divisions. This is the first report about the presence of a Second Division Restitution mechanism (SDR) which causes the formation of 2n pollen in the genus Agave. The genetic implications of the presence of 2n pollen in the genus Agave are discussed.

UNLABELLED PREMISE OF THE STUDY Teosinte species are the closest relatives of maize and represent an important but increasingly rare genetic resource for maize improvement and the study of evolution by domestication. Three morphologically and ecologically distinct teosinte populations were recently discovered in Mexico. The taxonomic status of these rare and endangered populations was investigated by detailed comparisons to previously characterized wild Zea species. • METHODS Three new teosinte populations were compared to known teosinte taxa on the basis of morphological, ecogeographic, cytological, and molecular characteristics. Phenetic and phylogenetic analyses were performed using morphological and molecular data, respectively. • KEY RESULTS The newly discovered populations are distinct from each other and from other Zea species to represent three new entities based on their unique combinations of morphological, ecological, ploidy, and DNA markers. A perennial diploid population from Nayarit is distinguished by early maturing plants, and having male inflorescences with few tassel branches and long spikelets. A perennial tetraploid population from Michoacan is characterized by tall and late maturing plants, and having male inflorescences with many branches. An annual diploid population from Oaxaca is characterized by having male inflorescences with fewer branches and longer spikelets than those found in the sister taxa Z. luxurians and Z. nicaraguensis, plants with high thermal requirements, and very long seed dormancy. • CONCLUSIONS Evidence from multiple independent sources suggests placement of the three new populations of teosinte as distinct entities within section Luxuriantes of the genus Zea. However, more extensive DNA marker or sequence data are required to resolve the taxonomy of this genus.

With the aim of utilizing allotriploid (2n = 3x = 36) lily hybrids (Lilium) in introgression breeding, different types of crosses were made. First, using diploid Asiatic lilies (2n = 2x = 24), reciprocal crosses (3x − 2x and 2x − 3x) were made with allotriploid hybrids (AOA) obtained by backcrosses of F1 Oriental × Asiatic hybrids (OA) to Asiatic cultivars (A). Secondly, the AOA allotriploids were crossed with allotetraploid (OAOA, 2n = 4x = 48), in 3x − 4x combination. Finally, the AOA allotriploids where crossed to 2n gamete producer F1 OA hybrids (3x − 2x (2n)). Two types of triploids were used as parents in the different types of crosses, derived from: (a) mitotic polyploidization and (b) sexual polyploidization. Ploidy level of the progeny was determined by estimating the DNA values through flowcytometry as well as chromosome counting. The aneuploid progeny plants from 3x − 2x and reciprocal crosses had approximate diploid levels and in 3x − 4x crosses and 3x − 2x (2n) the progeny had approximate tetraploid levels. Balanced euploid gametes (x, 2x and 3x) were formed in the AOA genotypes. Recombinant chromosomes were found in the progenies of all crosses, except in the case of 2x − 3x crosses through genomic in situ hybridization (GISH) analyses. Recombinant chromosomes occurred in the F1 OA hybrid when the triploid AOA hybrid was derived through sexual polyploidization, but not through mitotic polyploidization with two exceptions. Those recombinant chromosomes were transmitted to the progenies in variable frequencies.

Intergenomic recombination was assessed in a BC1 population of Oriental (O) × Asiatic (A) lilies (Lilium) backcrossed to Asiatic parents. This population consisted of 38 plants generated from the 2n gametes from 2 genotypes (951502-1 and 952400-1) of the diploid F1, Oriental × Asiatic lilies (2n = 2x = 24) as parents. In the majority of BC1 plants, there was evidence that first division restitution, with and without crossovers, resulted in functional gametes. However, there were 5 BC1 plants in which 2n gametes originated from indeterminate meiotic restitution (IMR). Based on the number of recombinant chromosomes for a particular homoeologous pair, 3 types of plants were identified: (i) those with both the reciprocal product of a crossover (O/A, A/O, where O represents the centromere of the O genome and A the recombinant segment of Asiatic chromosome, and vice versa); (ii) those with 1 normal chromosome of the O genome and a recombinant chromosome (O, A/O); and (iii) those with 1 normal chromosome of the A genome and a recombinant chromosome (A, O/A). An important feature of A × OA backcross progeny is the occurrence of substitutions for the segment distal in the crossover wherever the recombinant chromosome O/A was present. In the case of IMR, the substitution occurred for both proximal and distal recombinant segments. The significance of these substitutions is that they offer the potential for the phenotypic expression of recessive genes in polyploids (i.e., nulliplex genotype).Key words: genomic in situ hybridization (GISH), fluorescence in situ hybridization (FISH), unreduced gametes, allopolyploid.

In an effort to transfer Botrytis resistance from Oriental lilies to Asiatic hybrids (Lilium, 2n=2x=24) we made a large number of F1 hybrids between these two distantly related species. Because these species belong to two different taxonomic sections, the F1 hybrids were totally sterile and could not be directly used in breeding. Therefore, two approaches were used for utilizing the F1 hybrids. First, the somatic chromosome number of the F1s was doubled by treating with oryzalin that resulted in allotetraploids (mitotic doubling). These allotetraploids were used for crossing with the parents. Second, 2n gametes were used directly for crossing with the parents for producing sexual polyploids (meiotic doubling). The two types of BC1 progenies were monitored for resistance against Botrytis elliptica through a ¿leaf tip test¿. Disease severity was evaluated on a nominal scale, ranging from 1 resistant (no lesions) to 6 (a high degree of necrosis with mycelium or even spores). In both populations the resistance varied from very susceptible to highly resistant. However, the occurrence of transgression of resistance, meaning that the degree of resistance in some seedlings exceeded that of the parent, was higher in meiotically doubled polyploids as compared to those derived from mitotic doubling. This was explained from the fact that the typical allotetraploids produce uniformly a single genotype of 2x gametes containing both parental genomes because of autosyndetic pairing so that there is no scope for genetic variation. On the contrary, in the case of meiotic polyploids intergenomic recombination occurs between the alien chromosomes that could lead to considerable amount of genetic variation. This phenomenon might be an explanation for the observed transgression of Botrytis resistance in the meiotic polyploid progenies.

The mechanism of SDR 2n-pollen formation was analyzed in two intra-sectional diploid (2n = 2x = 24) Lilium hybrids (Enchantment x L. pumilum). Variable frequencies of 2n-pollen were found. Meiotic analysis indicated that the intra-sectional hybrids showed perfect chromosome pairing in most cases at metaphase I and normal anaphase I movement of pollen mother cells (PMCs), but produced 2n-pollen by second division restitution (SDR). A high bivalent formation (11.9II and 11.8II, respectively) at metaphase 1, irregular meiotic division such as unbalanced chromosome separation and chromatic fragmentation resulted yet in acceptable pollen fertility for cross-pollination. The hybrids were fertile, and when used as male parents, offspring could tie generated. The significance of the occurrence of 2n-pollen for the breeding of lilies was analyzed.

Sugarcane tissues subcultured for over 4 years had lost the capability to differentiate shoots. In freshly isolated tissues from 3 cultivars, we readily obtained shoot differentiation on Murashige-Skoog medium, but shoot differentiation was lost, apparently irreversibly, after more than one subculture on a modified White's medium. Tissue from a fourth cultivar produced only roots. The tissue cultures of all cultivars studied have the capability to form roots regardless of the length of time in culture; root formation was enhanced by treatment with dalapon (2,2-dichloropropionic acid).