Meiotic behaviour and pollen fertility in the seventeen
Transcrição
Vol. 55, no. 4: 341-347, 2002 CARYOLOGIA Meiotic behaviour and pollen fertility in the seventeen Brazilian species of Adesmia DC. (Leguminosae) SOLANGE BOSIO TEDESCO1, MARIA TERESA SCHIFINO-WITTMANN*, 2 and MIGUEL DALL’AGNOL2 1 Departamento de Biologia, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil. 2 Departamento de Plantas Forrageiras e Agrometeorologia, Faculdade de Agronomia, UFRGS. Caixa Postal 776. 91501-970 Porto Alegre, RS, Brazil. Abstract - The southern region of Brazil, especially Rio Grande do Sul State, is famous for its natural pastures. Many of the native legume species are potentially good forages. Among them are some of the 17 diploid (2n=20) species and one variety of Adesmia DC described for Brazil. Meiotic behaviour, meiotic indexes and pollen fertility were studied in 38 accessions of A. araujoi, A. arillata, A. bicolor, A. ciliata, A. incana (including one tetraploid accession), A. latifolia, A. muricata, A. psoraleoides, A. punctata, A. reitziana, A. riograndensis, A. rocinhensis, A. securigerifolia, A. tristis and A. vallsii. For A. paranensis and A. sulina only pollen data were available. Meiotic behaviour was essentially regular in most of the accessions, with 10 bivalents (II) at diakinesis and metaphase I and regular chromosome segregation at anaphase and telophase I and II. Uni, tri and quadrivalents were sometimes observed at diakinesis and metaphase I as well as laggards and bridges at anaphase and telophase I and II. Meiotic indexes and pollen fertility were normally over 90% or nearly 90%. However, in some accessions up to 30% of the cells presented abnormalities in chromosome pairing, chromosome segregation or low meiotic indexes or pollen fertility. From a taxonomic point of view neither chromosome number nor meiotic behaviour can be used to distinguish between the taxa analysed. Regarding an applied approach, as for example in planning crosses or in seed production for cultivated pastures, the absence of major meiotic anomalies and the high pollen fertility is an advantage. Key Words: Adesmia, forages, meiotic behaviour, pollen fertility, taxonomy. INTRODUCTION The southern region of Brazil, especially Rio Grande do Sul State, is famous for its native pastures, formed mainly by warm season species, the basis of cattle feeding. Due to a seasonal lack of forage during the winter months there is a search of native grass and legume species that could be intensively used as forages, directly or after selection and breeding procedures. One of the most promising genus is Adesmia DC. (Leguminosae, Faboideae, Adesmieae) which comprises around * Corresponding author: fax ++55 513 316 6045; e-mail: [email protected]. 200 annual and perennial, herbaceous and shrubby species endemic to South America, distributed along the Andes mountains, from northern Peru to Tierra del Fuego. The genus center of origin is supposed to be central Chile and western Argentina (BURKART 1967). Seventeen species and one variety are found in Brazil, all of them restricted to the southern part of the country, including Rio Grande do Sul, Santa Catarina and Paraná States (MIOTTO and LEITÃO-FILHO 1993). Several species of Adesmia from Southern Brazil present good growth during winter, are well adapted to the region environmental conditions, are widespread and have a high nutritional value. For example, A. latifolia 342 (Spreng.) Vog. has a good forage yield potential as well as high mineral content (SCHEFFER-BASSO et al. 2000, 2001). Crude protein percentages range from 6.9 to 17.5 in A. tristis Vog., 18.6 in A. latifolia, 17.9 to 21.5 in A. ciliata Vog., 19.7 in A. psoraleoides Vog. and 23.4 in A. punctata (Poir.) DC. (DALL’AGNOL and GOMES 1994). High crude protein, as well as in vitro organic matter digestibility values were also found for A. latifolia, A. tristis and A. punctata by SCHEFFERBASSO et al. (2000, 2001). Regarding mode of reproduction, A. latifolia is a versatile species, allowing self and cross fertilization (TEDESCO et al. 1998) as well as A. bicolor (Poir.) DC., A. muricata (Jacq.) DC., A. punctata and A. riograndensis Miotto, while A. incana Vog. reproduces by self-pollination and A. tristis mainly by cross-pollination. (TEDESCO et al. 2000a). There is strong evidence that A. securigerifolia Hert. is a self-pollinating species and A. arillata Miotto, A. ciliata, A. psoraleoides, A. rocinhesis Burk., A. reitziana Burk., A. sulina Miotto and A. vallsii Miotto are probably cross-pollinated (TEDESCO et al. 2000a). Cytogenetic studies in Adesmia are few. From literature data, chromosome numbers are known for less than 20% of the total number of species (FEDOROV 1969; GOLDBLATT 1981, 1984, 1985, 1988; GOLDBLATT and JOHNSON 1990, 1991, 1994, 1996, 1998, 2000). Most of the studied species are diploid with 2n=20 chromosomes, and a few are tetraploid (2n=40). Since the first chromosome number determinations in the genus, n=10 has been suggested as the genus basic number (CASTRONOVO 1945; COVAS and SCHNACK 1946; COVAS 1949; KRAPOVICKAS and KRAPOVICKAS 1951; COVAS and HUNZIKER 1954; RAHN 1960; HUNZIKER et al. 1985). For Brazilian species, chromosome numbers have been determined (MORAES-FERNANDES and BARRETO 1964; MIOTTO and FORNI-MARTINS 1995; COELHO 1996; COELHO and BATTISTIN 1998; TEDESCO et al. 2000b). Observations on chromosome morphology for some species (COELHO 1996), showed that most have small (ca. 1.5 to 2.5µm) meta and sub-metacentric chromosomes, with suggestions of inter-specific differences on the total chromosome complement length. Previous observations on meiotic behaviour of 12 accessions of seven species showed regular chromosome pairing and high meiotic indexes and pollen fertility (COELHO 1996; COELHO and BATTISTIN 1998). TEDESCO, SCHIFINO-WITTMANN and DALL’AGNOL As can be seen from literature data, a detailed and comparative analysis of meiotic behaviour and pollen fertility in all the 17 Brazilian Adesmia species was lacking, and therefore this was the objective of the present paper. This work is part of a multidisciplinary project on germplasm characterisation of the Brazilian Adesmia species, inserted in a broader research line of characterisation, utilisation and preservation of native species of the natural pastures of Rio Grande do Sul, developed at the Departamento de Plantas Forrageiras, Faculdade de Agronomia, Universidade Federal do Rio Grande do Sul, Brazil. MATERIAL AND METHODS Seeds from 41 accessions of the 17 Brazilian species were collected in several places of Rio Grande do Sul, Santa Catarina and Parana States (ca. 33º to 23º latitude South) (Table 1). Taxonomic vouchers of the mother plants are kept at the ICN (Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Brazil) and CENARGEM (Centro Nacional de Recursos Genéticos e Biotecnologia - EMBRAPA, Brazil) Herbaria. The seeds were scarified with sand paper, germinated in petri dishes with moistened filter paper in a growth chamber at 25º C and a 16h light- 8 h darkness photoperiod at the Cytogenetics Laboratory of the Universidade Federal de Santa Maria. The seedlings were transferred to plastic cups with soil when they reached 3 about cm height, and to 5 kg-capacity plastic pots when they were forty-five days old. The pots were kept in a greenhouse at the Forestry Department, Universidade Federal de Santa Maria, where the flower buds for meiotic analysis were collected. Young flower buds were collected and fixed in 3:1 ethanol-acetic acid for 24 h at room temperature, and afterwards transferred to 70% ethanol and kept at 4º C until slide preparation. For meiosis analysis, the slides were prepared by squashing the anthers in 1% acetic orcein. All observable phases of meiosis were analysed but a special emphasis was given to chromosome associations at diakinesis and metaphase I and chromosome segregation at anaphase and telophase I and anaphase and telophase II. Meiotic indexes (mi) were calculated according LOVE (1949), being considered as normal those tetrads with four equal-sized cells, and as abnormal any other formations. Around 300 tetrads (200600) per accession were examined. For pollen fertility (pf) estimation, the anthers were stained with 2% propionic carmine. Ten slides from different flowers generally from different inflores- 343 MEIOTIC BEHAVIOUR IN ADESMIA Table 1 – List of the Adesmia species and accessions examined. Species A. araujoi A. araujoi A. arillata A. arillata A. bicolor A. bicolor A. bicolor A. bicolor A. ciliata A. incana var. incana A. incana A. incana A. incana A. incana A. latifolia A. latifolia A. muricata A. muricata A. muricata A. paranensis A. psoraleoides A. psoraleoides A. psoraleoides A. psoraleoides A. psoraleoides A. punctata var. hilariana A. punctata A. reitziana A. riograndensis A. riograndensis A. rocinhensis A. rocinhensis A. securigerifolia A. securigerifolia A. securigerifolia A. securigerifolia A. sulina A. tristis A. tristis A. vallsii A. vallsii Accessiona V 10730 SB s/n V 11318 V 11346 V 9688 V 12243 V 12340 Mi 1512 V 8183 Te s/n V 9636 V 9637 V 9654 V 10288 EEL 15025 Zm 1775 V 9570 Zm 236 V 10289 Te s/n V 10760 V 11355 V 11425 Mi 1564 V 11325 V 6885 V 10812 Mi 1630 V 9590 Zm 419 V 7470 V 11507 V 6978 V 9615 Te s/n Te s/n V 11500 V 10766 V 10814 V 11439 V 11465 Codeb BRA-000817 BRA-001473 BRA-000825 BRA-000841 BRA-000183 BRA-000892 BRA-000884 BRA-001520 BRA-000272 BRA-001503 BRA-000604 BRA-000311 BRA-000329 BRA-001015 BRA-001732 BRA-001414 BRA-000485 BRA-001040 BRA-001058 BRA-001716 BRA-001066 BRA-001082 BRA-001091 BRA-001724 BRA-001074 BRA-001104 BRA-001112 BRA-001708 BRA-000761 BRA-001139 BRA-000116 BRA-001163 BRA-000060 BRA-000621 BRA-001481 BRA-001490 BRA-001261 BRA-001317 BRA-001325 BRA-001368 BRA-001384 Place of collectionc Soledade, RS Passo Fundo, RS Guarapuava, PR Guarapuava, PR Uruguaiana, RS São Borja, RS Dom Pedrito, RS Bagé, RS Lages, SC Bagé, RS Santana Livramento, RS Santana Livramento, RS Quaraí, RS Bagé, RS SC Imbé, RS Canguçú, RS Caçapava do Sul, RS Caçapava do Sul, RS Santiago, RS Lagoa Vermelha, RS Guarapuava, PR Abelardo Luz, SC Vargem Bonita, SC Guarapuava, PR Vacaria, RS Vacaria, RS Urubici, SC Santana da Boa Vista, RS Caçapava do Sul, RS São Joaquim, SC Palmas, PR Bagé, RS Bagé, RS Bagé, RS Bagé, RS Água Doce, SC Vacaria, RS Vacaria, RS Palmas, PR Palmas, PR collector’s number code number at EMBRAPA-CENARGEN c PR-Paraná State; RS-Rio Grande do Sul State; SC-Santa Catarina State a b cences were prepared per accession and the number of stained (viable) and empty (sterile) grains were recorded (Fig. 1). At least 1000 pollen grains were examined per plant. RESULTS AND DISCUSSION Meiotic behaviour, meiotic indexes and pollen fertility were studied in 38 accessions of A. araujoi Burk. A. arillata, A. bicolor, A. ciliata, A. incana, A. latifolia, A. muricata, A. psoraleoides, A. punctata, A. reitziana, A. riograndensis, A. rocinhensis, A. securigerifolia, A. tristis and A. vallsii. For A. paranensis Burk., A. sulina and one accession of A. psoraleoides only data on pollen fertility was available (Table 2). All accessions examined were diploid, 2n=20, except the tetraploid A. incana V 9637. Meiotic behaviour was essentially regular in most of the accessions, with 10 bivalents (II) at diakinesis and metaphase I (Fig. 2) and normal chromosome segregation at anaphase and telophase I and II. Uni (I), tri (III) and quadrivalents (IV) were eventually observed as well as irregular segregation and laggards and bridges at 344 TEDESCO, SCHIFINO-WITTMANN and DALL’AGNOL Fig. 1 – Fertile (stained) and sterile (empty) pollen grains in A. securigerifolia. Scale Bar 4µm. Fig. 2 – Diakinesis with 10 II in A. arillata. Scale Bar 4 µm. anaphase I and II. Meiotic indexes were normally over 90%, indicating meiotically stable plants (LOVE 1949), or nearly 90%. The abnormalities at this stage included mostly dyads and triads. Pollen fertility was also high, over 90%, for most accessions (Table 2). The main deviations from normality were observed in A. latifolia Zm 1775 (20% of cells with trivalents and/or univalents), A. muricata V 9570 (15% of cells with trivalents and/or univalents), A. muricata Zm 236 (20% of the cells with one quadrivalent), A. arillata V 11318 (mi 68.89, pf 43.77), A. incana V 9636 (pf 76.76), A. muricata V 10289 (pf 61,13), A. paranensis Te s/n (pf 61.13), A. psoraleoides V 11325 (pf 13.47). The only case in which a relation between meiotic anormalities and rather low meiotic meiotic indexes could be suggested was A. ciliata V 8183 (30% of the cells with univalents, 30% of cells with laggards at anaphase I or anaphase II, im 67,89) although pollen fertility was over 90%. For A. paranensis Te s/n and A. psoraleoides V 11325 only pollen fertility data were obtained. As meiotic behaviour was not analysed in V 11325, it could not be verified if the very low pollen fertility (13.47) were due to irregularities during meiosis. The tetraploid accession of A. incana (V 9637) presented regular meiosis with 20II at metaphase I, normal segregation at anaphase I and II and very high meiotic index and pollen fertility (Table 2), confirming a previous work by COELHO and BATTISTIN (1998). Tetraploid accessions have been reported in A. incana by other researchers (CASTRONOVO 1945; HUNZIKER et al. 1985; MIOTTO and FORNI-MARTINS 1995). If this accession is supposed to be of autotetraploid origin, as the absence of any trait distinguishing it from the conspecific diploid accessions may suggest, strong forces to a strict bivalent pairing, such as cytological diploidisation are expected to be acting, but due to the lack of additional studies, any suggestions on this matter are purely speculative. The results show that, apart from a few exceptions, most of the natural populations of the Adesmia species studied have a regular meiotic behaviour and high pollen fertility. From a taxonomic point of view neither chromosome number nor meiotic behaviour could be used to distinguish between the taxa analysed. Regarding an applied approach, as for example in planning crosses for breeding, or in seed production for cultivated pastures, the absence of major meiotic anomalies and the generally high pollen fertility is an advantage. Concluding remarks Cytogenetic studies in Adesmia should be intensified. The results reported in this paper are 345 MEIOTIC BEHAVIOUR IN ADESMIA Table 2 - Meiotic associations, chromosome segregation, meiotic indexes and pollen fertility in Brazilian species of Adesmia. Species A. araujoi A. araujoi A. arillata A. arillata A. bicolor A. bicolor A. bicolor A. bicolor A. ciliata A. incana var. incana A. incana A. incana A. incana A. incana A. latifolia A. latifolia A. muricata A. muricata A. muricata A. paranensis A. psoraleoides A. psoraleoides A. psoraleoides A. psoraleoides A. psoraleoides A. punctata var. hilariana A. punctata A. reitziana A. riograndensis A. riograndensis A. rocinhensis A. rocinhensis A. securigerifolia A. securigerifolia A. securigerifolia A. securigerifolia A. sulina A. tristis A. tristis A. vallsii A. vallsii Accessions Diakinesis/Metaphase I Anaphase I/TelophaseI Anaphase II/Telophase II number of cells chromosome associations number chromosome of cells segregation number of cells chromosome segregation 33 16 48 10 60 59 63 41 (18)a 10 II 10 II 10 II 10 II 10 II 10 II 10 II 10 IIa 63 10 19 21 56 71 16 14 regular regular regular regular regular regular regular regular 25 28 10 4 26 84 12 44 (13)b regular regular regular regular regular regular regular regular b 97.59 97.59 68.89 67.21 97.99 96.30 93.28 99.10 67.89 99.15 95.11 43.77 61.13 98.78 99.46 95.76 97.93 94.83 Te s/n V 9636 V 9637 V 9654 V 10288 EEL 15025 Zm 1775 V 9570 Zm 236 V 10289 Te s/n V 10760 V 11355 V 11425 Mi 1564 V 11325 19 159 62 48 11 98 53 (10)c 118 (20)d 29 (8)e 18 10 II 10 II 20 II 10 II 10 II 10 II 10 IIc 10 IId 10 IIe 10 II 30 156 44 12 23 36 32 17 6 14 regular regular regular regular regular regular regular regular regular regular 12 31 25 30 42 11 24 54 15 18 regular regular regular regular regular regular regular regular regular regular 94.93 91.50 96.67 88.43 95.94 95.65 91.15 80.69 75.72 98.36 40 10 7 115 10 II 10 II 10 II 10 II 14 18 regular regular 28 8 regular regular 23 regular 49 regular 86.30 98.00 100.00 93.55 99.22 76.76 99.64 99.61 97.56 98.95 97.89 92.98 90.11 97.19 67.49 98.01 97.99 97.22 92.61 13.47 V 6885 V 10812 Mi 1630 V 9590 Zm 419 V 7470 V 11507 V 6978 V 9615 Te s/n (BRA 001481) Te s/n (BRA 001490) V 11500 V 10766 V 10814 V 11439 V 11465 3 25 24 11 63 68 12 19 12 10 II 10 II 10 II 10 II 10 II 10 II 10 II 10 II 10 II 4 107(18)f 33 16 78 15 100 64 3 regular regular regular regular regular regular regular regular regular 33 55 10 regular regular regular 50 9 84 32 26 regular regular regular regular regular 82.41 81.08 100.00 94.79 84.50 97.98 91.92 97.16 19 10 II 88 regular 34 regular 93.26 10 10 II 6 regular 27 regular 95.48 25 32 20 36 10 II 10 II 10 II 10 II 24 30 12 26 regular regular regular regular 19 33 13 30 regular regular regular regular 96.93 96.72 98.25 99.14 V 10730 SB s/n V 11318 V 11346 V 9688 V 12243 V 12340 Mi 1512 V 8183 18 cells with 1-4 univalents 13 cells with irregular segregation or 1-3 laggards c 10 cells with one trivalent and/or 1-2 univalents d 20 cells with one trivalent and/or 1-8 univalents e 8 cells with univalents or quadrivalents f 18 cells with irregular segregation or 1-2 laggards a b Meiotic index Pollen fertility (%) (%) 99.76 86.10 82.60 99.24 99.68 90.74 87.58 98.69 98.30 96.78 99.63 98.89 97.57 97.32 346 TEDESCO, SCHIFINO-WITTMANN practically non-existent for other species besides the Brazilian ones. A broader survey of chromosome numbers, as well as the analysis of meiotic behaviour and pollen fertility in other species apart from the Brazilian taxa, and verification of intraspecific variability in chromosome number as such found in A. incana should be done to a better cytogenetic characterization of the genus. Especifically for the Brazilian species, an examination of more accessions, mainly of the poorly analysed A. sulina and A. paranensis should be undertaken. Acknowledgments – To Dr. José Francisco Montenegro Valls, EMBRAPA-CENARGEN for most of the seedlots and for his continual support for our work. To Dr. Alice Battistin and Dr. Juarez Hope, Universidade Federal de Santa Maria, for allowing the utilisation of their laboratory and greenhouse facilities. To Moises Stefanello for his help in the pollen analyis. To CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico), Brazil, for finnancial support and to CAPES (Comissão de Aperfeiçoamento de Pessoal de Ensino Superior), Brazil for the PhD scholarship to the first author. REFERENCES BURKART A., 1967 – Sinópsis del género sudamericano de Leguminosas Adesmia DC. Darwiniana, 14: 463-568. CASTRONOVO A., 1945 – Estudos cariologicos de doce especies de leguminosas argentinas. Darwiniana, 7: 38-57. COELHO L.G.M., 1996 – Citogenética e qualidade de forragem de espécies de Adesmia DC. nativas no Rio Grande do Sul. MSc Thesis, Universidade Federal de Santa Maria, Brazil. COELHO L.G.M. and BATTISTIN A., 1998 – Meiotic behavior of Adesmia DC. (LeguminosaeFaboideae) species native to Rio Grande do Sul, Brazil. Genetics and Molecular Biology, 21: 403406. COVAS G., 1949 – Estudios cariológicos em antófitas, III Parte. Darwiniana, 9: 158-162. COVAS G. and HUNZIKER J.H., 1954 – Estudos cariológicos em antófitas. IV Parte. 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LOVE R.M., 1949 – La citologia como ayuda practica al mejoramiento de los cereales. Revista Argentina Agronomia, 16: 1-13. MIOTTO S.T.S. and FORNI-MARTINS E.R., 1995 – Número cromossômico em espécies brasileiras de Adesmia DC. (Leguminosae, Faboideae). Acta botanica Brasilica, 8: 3-9. MIOTTO S.T.S. and LEITÃO FILHO H.F., 1993 – Leguminosae-Faboideae, Gênero Adesmia DC. Boletim do Instituto de Biociências, 52: 1-157. MORAES-FERNANDES M.I.B and BARRETO I., 1964 – Estudos citotaxonômicos das pastagens nativas do RGS. Anais Congresso Sociedade Botânica do Brasil, 15. MEIOTIC BEHAVIOUR IN ADESMIA RAHN K., 1960 – Chromosome numbers in some South American angiosperms. Botanisk Tidsskrift, 56: 117-127. SCHEFFER-BASSO S.M.S., JACQUES A.V.A., DALL’AGNOL M., RIBOLDI J. and CASTRO S.M.J., 2000 – Dinâmica da formação de gemas, folhas e hastes de espécies de Adesmia DC. e Lotus L. Revista da Sociedade Brasileira de Zootecnia, 29: 1961-1968. –, 2001 – Disponibilidade e valor nutritivo de forragem de leguminosas nativas (Adesmia DC.) e exóticas (Lotus L.). Revista da Sociedade Brasileira de Zootecnia, 30: 975-982. TEDESCO S.B., DALL’AGNOL M. and SCHIFINOWittmann M.T., 1998 – Observações sobre o 347 modo de reprodução em Adesmia latifolia Spreng.Vog. Ciência Rural, 28: 141-142. T EDESCO S.B., D ALL ’A GNOL M., S CHIFINO WITTMANN M.T. and VALLS J.F.M., 2000a – Mode of reproduction of Brazilian species of Adesmia DC. (Leguminosae). Genetics and Molecular Biology, 23: 475-478. TEDESCO S.B., SCHIFINO-WITTMANN M.T., MIOTTO S.T.S., BATTISTIN A. and VALLS J.F.M., 2000b – Determinação do número de cromossomos e comportamento meiótico em espécies de Adesmia DC. (Leguminosae). Genetics and Molecular Biology 23, (Suppl): 380. Received April 26, 2002; accepted June 26, 2002
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