Botanical aspects of Heteropterys umbellata (Malpighiaceae): a cytological and palynological approach

The genus Heteropterys is one of the major genera in Malpighiaceae. However, few cytological and palynological studies were reported. The present work described for the first time the chromosome number, heterochromatin pattern, meiotic behavior, pollen viability and palynological aspects of Heteropterys ubellata, a very spread species. One large Brazilian population was evaluated using conventional techniques for meiotic studies and acetolyse to access the pollen morphology. The species showed 2n = 20 chromosomes, normal meiotic development and viable pollens. Great blocks of heterochromatin were observed around the centromers. DAPI staining was positive for centroeric heterochroatin, hile CMA3 ark as observed just at terinal regions of one pair of hoologues chromosomes. This result and the presence of one chromosome pair attached to the nucleoli during the pachytene and diakinesis suggested the presence of only one pair of NORs. Palynological analysis revealed that pollen grains are apolar, 6 porate and with colpoids associated to all pores. The pollen content was positive for the starch test, and the exine was rugulate with little psilate regions.

O gênero Heteropterys é um dos maiores gêneros entre as Malpighiaceae. Entretanto, poucos estudos citológicos e palinológicos foram relatados. O presente trabalho descreveu pela primeira vez o número cromossômico, o padrão heterocromático, o comportamento meiótico, a viabilidade polínica e aspectos palinológicos de Heteropterys umbellata, uma espécie muito disseminada. Uma grande população brasileira foi estudada utilizando técnicas convencionais para o estudo de cromossomos meióticos e acetólise para acessar a morfologia polínica. A espécie apresentou 2n = 20 cromossomos, desenvolvimento meiótico normal e pólens viáveis. Grandes blocos de heterocromatina foram observados ao redor dos cen-trômeros. A coloração com DAPI foi positiva para a hetero-cromatina centromérica, enquanto marcas com CMA3 foram observadas somente em um sítio terminal de um par de cromossomos homólogos. Este resultado e a presença de um par de cromossomos associados a um nucléolo durante o paquíteno e diacinese sugerem a presença de somente um par de RONs. A análise palinológica revelou que os grãos de pólen são apolar, com 6 poros e colpóides associados a todos eles. O conteúdo polínico foi positivo para o teste de amido e a exina mostrou-se rugulada com poucas regiões psiladas.

Ability of Allium cepa L. root tips and Tradescantia pallida var. purpurea in N-nitrosodiethylamine genotoxicity and mutagenicity evaluation

N-nitroso compounds, such as N-nitrosodiethylamine (NDEA), can be formed by the reaction of secundary amines with nitrosating agents, and are suspected to be involved in tumors in humans. NDEA has been considered a weak carcinogen in genotoxic assays probably due to the inefficient nitrosamine activation system that is used and/or to the efficient repair system. In this work, we evaluated the sensibility of Allium cepa L. root tips and Tradescantia stamen hair mutation assay (Trad-SH) using Tradescantia pallida var. purpurea for NDEA (0.1; 0.5; 5 and 25mM) genotoxicity and mutagenicity induction. Allium cepa L. was treated with different NDEA concentrations for 3h, for 3 consecutive days, including negative control (distilled water) and positive control maleic hydrazide (MH 30mg/mL). After treatment, the roots were hydrolyzed, squashed, and the mitotic index (MI) and cytological abnormalities were scored. The results revealed a cytostatic effect of NDEA (0.5 and 5mM), showing a significant reduction in the MI. Chromosome stickiness suggests a NDEA toxic effect. T. pallida purpurea did not respond to mutagens with a dose-dependent pattern. In conclusion, our study indicates that the root tips of Allium cepa L. have sensibility to detect NDEA genotoxicity, but not for Trad-SH test.

Nitrocompostos, como N-nitrosodietilamina (NDEA), podem ser formados pela reação entre uma amina secundária e agentes nitrosantes e são suspeitos de estarem envolvidos na formação de tumores em humanos. NDEA é considerada um carcinógeno fraco e ensaios genotóxicos provavelente pela utilização de um sistema de ativação ineficiente e/ou pela utilização de um eficiente sistema de reparo. Neste trabalho, nós avaliamos a sensibilidade de ensaios com Alliu cepa L. e Tradescantia pallida var. purpurea (Trad-SH) à genotoxicidade e mutagenicidade induzidas por diferentes concentrações de NDEA (0,1; 0,5; 5 e 25mM) por 3h, por 3 dias consecutivos, incluindo controle negativo (água destilada) e controle positivo, hidrazida maleica (MH 30mg/mL). Depois do tratamento, as raízes foram hidrolizadas, esmagadas e o índice mitótico (IM) e anormalidades citológicas foram contadas. Os resultados revelaram um efeito citostático de NDEA (0,5 e 5mM), pela significante redução do IM. Chromosome stickiness sugere um efeito citotóxico de NDEA. T pallida purpurea não respondeu ao mutágeno com um padrão dose dependente. Em conclusão, nossos estudos indicaram que raízes de Allium cepa L. possue sensibilidade na detecção genotóxica de NDEA, mas não para o ensaio Trad-SH.

Evaluation of microsporogenesis in an interspecific Brachiaria hybrid (Poaceae) collected in distinct years

Microsporogenesis in an interspecific Brachiaria hybrid, grown in the field under natural environmental conditions in Brazilian savannas, was analyzed in three distinct years of collection. Several types of meiotic abnormalities were recorded during those three years, but varied in type and frequency depending on the year. The average temperature and rainfall 15 days before collection was unusually high in those years. The percentage of abnormal meiocytes recorded was 62% in 2001, 73% in 2004, and 77% in 2005. The abnormalities observed during microsporogenesis compromised pollen viability by generating unbalanced gametes or affecting nucleolus organization. The environmental conditions under which the hybrid was growing could have affected the genetic control of meiosis. More detailed studies, under controlled conditions, are necessary to better understand the effects of environmental factors on Brachiaria microsporogenesis hybrids.

Unusual chromosome numbers in Paspalum L. (Poaceae: Paniceae) from Brazil

Somatic chromosome numbers were determined for 20 new germplasm accessions of Paspalum, belonging to 17 species collected in Brazil. Chromosome number is reported for the first time for P. reduncum (2n = 18), P. cinerascens (2n = 20), P. cordatum (2n = 20), P. filgueirasii (2n = 24), P. ammodes (2n = 36), P. bicilium (2n = 40), P. heterotrichon (2n = 40), and P. burmanii (2n = 48). New cytotypes were confirmed for two germplasm accessions of P. carinatum (2n = 30) and P. trachycoleon (2n = 36), one of P. clavuliferum (2n = 40) and one of P. lanciflorum (2n = 40), indicating variability in these species. The remaining chromosome numbers reported here confirm previous counts. The unexpected chromosome numbers 2n = 18, 24, 36, and 48 in Paspalum species, which are usually shown to be multiples of 10, suggest that much more collection and cytogenetic characterization are necessary to assess the whole chromosomal and genomic multiplicity present in the genus, which seems to be much more diverse than currently thought to be.

Mitotic behavior in root tips of Brachiaria genotypes with meiotic chromosome elimination during microsporogenesis

Three accessions of Brachiaria brizantha, three of B. humidicola, and two interspecific hybrids between B. ruziziensis and B. brizantha were analyzed with regard to their mitotic behavior in root tips. All these genotypes revealed chromosome elimination or lack of chromosome affinity in previous analyses of microsporogenesis. Analyses of root tips showed a normal mitotic division in all accessions and hybrids, reinforcing the notion that the genetic control of meiosis is totally independent of that of mitosis. The implications of these findings for the Brachiaria breeding program are discussed.

Inestabilidad cariológica durante la formación de células madres del polen en Aloe vera (Aloaceae)

Con el objetivo de esclarecer la posible existencia de anomalías citogenéticas que aminoren la fertilidad del polen de Aloe vera, se analizó la etapa de proliferación celular que lleva a la formación de células madres del polen (CMPs). Se recolectaron botones florales (BF) en 25 plantas de una población ubicada a 10°34’15’’ N, 64°12’08’’ W, los cuales fueron fijados en Carnoy I por 24 h y almacenados en etanol (70 % v/v). Las observaciones se realizaron en preparaciones temporales obtenidas por la tinción del contenido de las anteras suspendidas en orceína acética (1.5 % p/v) por 5 minutos. De las 9 411 células analizadas, 17 % mostraron 1-8 puentes entre cromátidas hermanas, 13 % 1-7 micronúcleos de 0.9-4.8 µm, 8.1 % estaban unidas por puentes y 0.1 % no contenían cromatina. El resto de las células (61.8 %) presentó configuraciones aparentemente normales y sin variaciones morfométricas. La proliferación irregular de una fracción de CMPs (39.2 %) sugiere que las condiciones ambientales de la zona árida donde se realizaron los muestreos inducen inestabilidad cromosómica y cambios fisiológicos que afectan el normal desarrollo de la mitosis premeiótica, generando pérdida o adición de fragmentos, asociados a deficiencias y duplicaciones génicas.

Origin of new Brassica types from a single intergeneric hybrid between B. rapa and Orychophragmus violaceus by rapid chromosome evolution and introgression.

Many novel lines were established from an intergeneric mixoploid between Brassica rapa (2n = 20) and Orychophragmus violaceus (2n = 24) through successive selections for fertility and viability. Pedigrees of individual F(2) plants were advanced to the 10th generation by selfing. Their breeding habit was self-compatible and different from the self-incompatibility of their female parent B. rapa, and these lines were reproductively isolated to different degrees from B. rapa and B. napus. The lines with high productivity showed not only a wide spectrum of phenotypes but also obvious variations in fatty acid profiles of seed oil and glucosinolate contents in seed meal. These lines had 2n = 36, 37, 38, 39 and 40, with 2n = 38 being most frequent (64.56%), and no intact O. violaceus chromosomes were detected by genomic in situ hybridization (GISH) analysis. Amplified fragment length polymorphism (AFLP) analyses revealed a high extent of variation in genomic compositions across all the lines. O. violaceus-specific bands, deleted bands in B. rapa and novel bands for two parents were detected in these lines, with novel bands being the most frequent. The morphological and genetic divergence of these novel types derived from a single hybrid is probably due to rapid chromosomal evolution and introgression, and provides new genetic resources for rapeseed breeding.

Molecular phylogenetic relationships among four species of the mangrove tree genus Bruguiera (Rhizophoraceae), as revealed by chromosome and RAPD markers

Analysis of karyotype, nuclear DNA content and RAPD markers were performed in four species of Bruguiera (Rhizophoraceae) of Bhitarkanika mangrove forests, Orissa, India. Detailed karyotype analysis revealing 2n=34 in B. cylindrica and 2n=36 in B. gymnorrhiza was reported for the first time and 2n=34 in B. parviflora and B. sexangula was confirmed. On the basis of the common types of chromosomes present among Bruguiera, two distinct groups were found; one consists of B. cylindrica and B. parviflora and the other of B. gymnorrhiza and B. sexangula. The symmetrical karyotype with same chromosome types grouped B. cylindrica and B. parviflora together and presence of Type E chromosomes placed B. gymnorrhiza and B. sexangula in a separate group, suggesting their closer affinity in their respective group. Analysis of chromosome length, volume, INV and 4C DNA content confirmed this division. Nuclear DNA content was two-fold higher (~17.0 pg) in the second group than in the first (~8.0 pg). The amplification products generated through RAPD revealed 1-9 amplicons with size variations from 600 bp to 2 500 bp with 49.31% genetic similarity between B. gymnorrhiza and B. sexangula and 47.10% in between B. cylindrica and B. parviflora. The high copy number marker band (~ 1 100 bp) yielded in OPN-15 primer in B. parviflora the characteristic DNA marker, which was cloned and used as probes for assessment of genetic diversity, and demonstrated its close genetic affinity to B. cylindrica. B. gymnorrhiza and B. sexangula also produced similar marker bands of ~600 bp and ~2 200 bp in the same primer. All of the cytological, 4C DNA content and RAPD data confirmed the existence of two taxonomically distinct groups of Bruguiera: one consisting of B. cylindrica and B. parviflora and the other of B. gymnorrhiza and B. sexangula as placed earlier (1862) in the tribe Rhizophoreae by Bentham and Hooker, on the basis of the flowering habits of Bruguiera. Genetically, the B. sexangula and B. gymnorrhiza group was found to be very closely, rather than distantly, related to B. parviflora and B. cylindrica. Our results demonstrate that molecular markers together with cytological evidence provide an effective tool to access the existing interspecific genetic polymorphism in mangrove species, to solve the taxonomic problems and to design their conservation strategy. Rev. Biol. Trop. 55 (2): 437-448. Epub 2007 June, 29.

Estudiamos cuatro especies del mangle Bruguiera (Rhizophoraceae) en Orissa, India. Los cromosomas indican queB. cylindrica y B. parviflora son un grupo taxonómico, y que B. gymnorrhiza y B. sexangula son otro. Genéticamente, el par B. sexangula y B. gymnorrhiza está cercanamente emparentado con B. parviflora and B. cylindrica. Nuestros datos indican que el uso combinado de marcadores genéticos y evidencia citológica permiten discernir el polimorfismo genético interespecífico en los mangles, tanto para resolver problemas taxonómicos como para diseña estrategias eficaces de conservación.

Microsporogenesis in inbred line of popcorn (Zea mays L)

Endogamy places genes for several characteristics in homozygosis, which include those related to meiosis causing abnormalities that may impair gamete viability. An original population (S0) of popcorn (CMS-43) produced by Embrapa Maize and Sorghum was self-pollinated for seven years, generating inbred lines (S1 to S7). Conventional studies of microsporogenesis revealed that meiotic abnormalities did not increase with endogamy. Univalent chromosomes, irregular chromosome segregation, abnormal cell shape, partial asynapsis, cell fusion, absence of cytokinesis, abnormal spindle orientation, and chromosome stickiness were recorded in low frequency in meiocytes. Since the frequency of abnormalities was low, mainly in S7, inbred lines from CMS-43 have a high potential for hybridization.

Multicolor fluorescence in situ hybridization with combinatorial labeling probes enables a detailed karyotype analysis of Larix principis-rupprechtii

The chromosomes (2n = 2x = 24) of Larix principis-rupprechtii are composed of six pairs of large metacentrics and six pairs of medium-sized submetacentrics. The identification of homologous pairs is hampered by their high degree of similarity at the morphological level in each group. As one of the most extensively used methods in molecular cytogenetics producing chromosome landmarks, fluorescence in situ hybridization (FISH) has significantly facilitated karyotype construction, especially in species with morphologically similar chromosomes. This study developed a simple but effective use of combinatorial labeling probes to distinguish chromosomes of Larix principis-rupprechtii by multicolor FISH. Three highly repetitive sequences in Larix were selected: 25S rDNA hybridized at all of the secondary constrictions of two pairs of metacentrics and the largest pair of submetacentrics; 5S rDNA hybridized at subtelomeric sites of one pair of metacentrics that also harboured 25S rDNA on different arms; LPD family sequences are tandem repeats hybridized at proximal regions of 22 chromosomes. The three different probes were labeled with only two different labels, hybridized to metaphase chromosomes of Larix principis-rupprechtii, simultaneously visualized, and unequivocally distinguished in a single FISH experiment. These multicolor FISH marks largely improved the karyotype analysis of Larix principis-rupprechtii.

B chromosomes in popcorn (Zea mays L. )

Cytological analysis of microsporogenesis in 72 popcorn plants, comprising nine from the original population (CMS-43, S0) and 63 from seven cycles of self-fertilization (S1 to S7), one plant of S0 generation (plant 2) was identified with B chromosomes. The number of B chromosomes varied from two to three in the same anther. The pattern of chromosome pairing and meiotic behavior of Bs were similar to those found in other plant species. The presence of B chromosomes did not affect chiasma frequency and chiasma distribution in A chromosomes. This is the first report of B chromosomes in popcorn

Estudio de la diversidad citogenetica de Physalis peruviana L. (Solanaceae) / Study of the cytogenetic diversity of Physalis peruviana L. (Solanaceae)

Se caracterizó el cariotipo de cinco ecotipos de Physalis peruviana L., tres silvestres distribuidas en los municipios de Villa de Leyva (Boyacá, Colombia), La Calera y Choachí (Cundinamarca, Colombia) y dos cultivados, uno de ellos nativo, el ecotipo Colombia distribuido en el municipio de Subachoque (Cundinamarca) y uno foráneo, procedente de Kenia, cultivado en el municipio de Paipa (Cundinamarca). Ápices radicales obtenidos a partir de semillas y de hojas en medios de cultivo in vitro enriquecidos con auxinas se emplearon para estandarizar el protocolo de obtención de cromosomas, con las diferentes técnicas de pretratamiento, fijación, hidrólisis y montaje de las muestras. Adicionalmente se evaluó la duración del ciclo celular para establecer la hora mitótica. Se encontró variabilidad genética entre los ecotipos evaluados. Los ecotipos silvestres presentaron una dotación cromosómica 2n=24, el ecotipo Colombia 2n=32 y el ecotipo Kenia 2n=48. Los ecotipos exhibieron también variación en las características morfológicas y anatómicas, que de acuerdo a la literatura, son un reflejo del nivel de ploidía, como altura, área foliar, número de estomas/mm2, número de cloroplastos en las células guarda de los estomas, diámetro de frutos, semillas y contenido de masa seca.

Visualization of the ribosomal DNA (45S rDNA) of Indica rice with FISH on some phases of cell cycle and extended DNA fibers

The ribosomal DNA (45S rDNA) behaviors during the cell cycle were analyzed on interphase nuclei, prophases, metaphases, pachytene chromosomes and extended DNA fibers in rice (Oryza,sativa ssp.indica cv.Guangluai No.4) by using high-resolution fluorescent in situ hybridization (FISH). The results show that 45S rDNA is located at the ends of short arms of chromosomes 9 and 10. But the signals are much more intense on chromosome 9 than on chromosome 10 in metaphase. Pachytene chromosome has rDNA signal arrays on chromosome 9. Different phases are described and discussed. These results indicate that the activity of rDNA at individual loci may also vary through the cell cycle in rice. on extended DNA fibers, 45S rDNA signals appear as strings of numerous red spots, but some signals are missed in some regions, probably result from weak signals or intergenic spacers

Reproductive studies on ipecac (Cephaelis ipecacuanha (Brot.) A. Rich; Rubiaceae): meiotic behavior and pollen viability

Estudos reprodutivos foram realizados em acessos brasileiros de poaia, Cephaelis ipecacuanha. O comportamento meiótico foi estudado usando a técnica de esmagamento. Foi observada segregação irregular de cromossomos durante meiose I e II, muitos grupos de cromossomos em telófase II, micronúcleos, divisão incorreta do citoplasma, citocinese incompleta e produtos pós-meióticos anômalos, principalmente políades. A média do índice meiótico foi inferior a 72%. A viabilidade polínica foi analisada utilizando-se solução de Alexander e a percentagem de pólen viável variou entre as formas florais, brevistila e longistila (85,3% a 93,1%), e entre as diferentes localidades (82,5% a 92,6%) analisadas. O tamanho do pólen variou entre viáveis e inviáveis, e entre os inviáveis vazios e contraídos. Em seu habitat natural, a poaia apresenta propagação por multiplicação vegetativa, mas a reprodução sexuada parece ser tão importante para essa espécie quanto a propagação vegetativa.

Cytogenetic evidence for genome elimination during microsporogenesis in interspecific hybrid between Brachiaria ruziziensis and B. brizantha (Poaceae)

Microsporogenesis was analyzed in an interspecific hybrid between an artificially tetraploidized sexual accession of Brachiaria ruziziensis (R genome) and a natural apomictic tetraploid accession of B. brizantha (B genome). Chromosomes associated predominantly as bivalents. From this phase to the end of meiosis, chromosomes presented irregular segregation and abnormal arrangement in the metaphase plate. During metaphase I, in 27.8 percent of meiocytes, bivalents were distributed in two metaphase plates. In anaphase I, two distinct and typical bipolar spindles were formed. In 29.7 percent of pollen mother cells, one genome did not divide synchronically, with chromosomes lagging behind or not segregating at all. The second division was very irregular, resulting in polyads. Based on previous results from analysis of a triploid hybrid between these species, where the R genome was eliminated by asynchrony during meiosis, it is suggested that the laggard genome in this hybrid also belongs to B. ruziziensis.

Microsporogenesis in Brachiaria dictyoneura (Fig. & De Not.) Stapf (Poaceae: Paniceae)

icrosporogenesis was analyzed in five accessions of Brachiaria dictyoneura presenting x = 6 as the basic chromosome number. All accessions were tetraploid (2n = 4x = 24) with chromosome pairing in bi-, tri-, and quadrivalents. The recorded meiotic abnormalities were those typical of polyploids, including precocious chromosome migration to the poles, laggard chromosomes, and micronucleus formation. The frequency of these abnormalities, however, was lower than those reported for other polyploid accessions previously analyzed for other Brachiaria species. Cell fusion and absence of cytokinesis were also recorded in some accessions, leading to restitutional nucleus formation in some cells. Genetically unbalanced microspores, binucleate, and 2n microspores were found among normal meiotic products as results from these abnormalities. The limitation in using these accessions as pollen donor in interspecific crosses with sexual species with x = 7 or x = 9 in breeding programs is discussed.

Evidence of allopolyploidy in Brachiaria brizantha (Poaceae: Paniceae) through chromosome arrangement at metaphase plate during microsporogenesis

In the hexaploid (2n = 6x = 54) accession B176 of Brachiaria brizantha, one cytological characteristic differentiated it from the other accessions previously analyzed with the same ploidy level. Nearly 40% of meiocytes displayed the chromosome set arranged at two metaphase plates at the poles of the cell, close to the membrane. In these cells, both metaphase plates were arranged in an angle to form a typical tripolar spindle. Therefore, cells did not show normal chromosome segregation at anaphase I. Only nine univalent chromosomes migrated from each plate to the opposite pole with the remainder staying immobile on the plate. As a result of such spindle orientation and chromosome behavior, trinucleate telophases I were recorded. After telophase, cytokinesis eliminated the small nuclei into a microcyte. The second division proceeded normally, with the presence of microcytes in all phases. The origin of such an abnormality was explained on the hexaploid level of the accession which could have resulted by chromosome doubling of a triploid derived from species that did not display the same behavior for spindle organization. The high percentage of meiotic abnormalities recorded in this accession compromises fertility and renders it inadequate for the breeding program.

Incongruent evolution of chromosomal size in rice

To investigate genome size evolution, it is usually informative to compare closely related species that vary dramatically in genome size. A whole genome duplication (polyploidy) that occurred in rice (Oryza sativa) about 70 million years ago has been well documented based on current genome sequencing. The presence of three distinct duplicate blocks from the polyploidy, of which one duplicated segment in a block is intact (no sequencing gap) and less than half the length of its syntenic duplicate segment, provided an excellent opportunity for elucidating the causes of their size variation during the post-polyploid time. The results indicated that incongruent patterns (shrunken, balanced and inflated) of chromosomal size evolution occurred in the three duplicate blocks, spanning over 30 Mb among chromosomes 2, 3, 6, 7, and 10, with an average of 20.3% for each. DNA sequences of chromosomes 2 and 3 appeared to had become as short as about half of their initial sequence lengths, chromosomes 6 and 7 had remained basically balanced, and chromosome 10 had become dramatically enlarged (approximately 70%). The size difference between duplicate segments of rice was mainly caused by variations in non-repetitive DNA loss. Amplification of long terminal repeat retrotransposons also played an important role. Moreover, a relationship seems to exist between the chromosomal size differences and the nonhomologous combination in corresponding regions in the rice genome. These findings help shed light on the evolutionary mechanism of genomic sequence variation after polyploidy and genome size evolution.

Microsporogenesis in tetraploid accessions of Brachiaria nigropedata (Ficalho & Hiern) Stapf (Gramineae)

The genus Brachiaria (Trin.) Griseb. has achieved considerable importance to cattle production systems, as a result of the good production and adaptation of a few cultivars to poor and acid soils of the Brazilian savannas. Many of its species and accessions are polyploid and apomictic, which limits direct hybridization. To assist the breeding program, cytogenetic characterization has been undertaken on the accessions of Brachiaria collection at the Embrapa Beef Cattle Research Center. In this study, chromosome number and meiotic behavior are reported for the Brachiaria nigropedata (Ficalho & Hiern) Stapf collection. The 20 available accessions are tetraploid (2n = 4x = 36). Chromosomes paired preferentially as bivalents, but quadrivalents were found in high frequencies in some cells. Meiotic behavior was, in general, irregular, and varied among accessions. Most accessions presented more than 20% of abnormal tetrads. The most common meiotic abnormalities were those related to irregular chromosome segregation due to polyploidy, leading to micronuclei formation in the tetrad stage. A low frequency of other meiotic abnormalities such as the absence of cytokinesis, chromosome stickiness, cell fusion, anaphase bridges, and chromosome transfer among microsporocytes were also recorded in some accessions. Limitations of these accessions for use in hybridization programs are discussed.