Resumo
Only one plant of Coffea arabica L. var. rugosa K.M.C., is available for study Its fruit production is very low. Of the progeny observed, none has reproduced th rugose condition of the leaves characteristic of the parent plant. Previous study ha shown that the rugose condition of the leaves could not be considered a somatic chimer because the tissues have a normal number (2n=44) of chromosomes. The present cytological study was undertaken in order to find out if the low yiel of the rugose variety could be related to abnormalities in microsporogenesis. The structure of the chromosomes in early prophase is difficult to study. In diaki nesis two pairs and sometimes three pairs of chromosomes appear to be attached to th nucleolus. Also in diakinesis it is possible to locate the centromere in the chromosoni pairs and to count the chiasmata. It was observed that an average of 6.6 bivalent show one single chiasma, 12.3 bivalents show two chiamata and 3.0 bivalents shoM three chiasmata. The average total number of chiasmata per cell at this phase is o 40.0, while at metaphase this number is reduced to 34.7. The first division in the mi crospore is normal and the resulting two nuclei differ in size and also in the size o their nucleolus. The polen grains are normal, giving 69% germination on a medium containinj 0,5% of agar and 15% of sucrose. It is concluded that microsporogenesis is normal and would not appear to be relate< to the low production of fruits of the rugosa variety. The fact that none of the progen¹ has reproduced the rugose condition might be due to the limited number of plants observed.
Observações citológicas em Coffea. XIV - Microsporogênese em Coffea arabica L. Var. rugosa K.M.C.(1 (1 ) Trabalho apresentado à Primeira Reunião Anual da Sociedade Brasileira para o Progresso da Ciência, realizada em Campinas, de 1 a 15 de outubro de 1949. (2 ) A autora expressa os seus agradecimentos ao engenheiro agrônomo Antônio José Teixeira Mendes pela orientação dada na execução dêste trabalho. )
Dixier M. Medina(2 (1 ) Trabalho apresentado à Primeira Reunião Anual da Sociedade Brasileira para o Progresso da Ciência, realizada em Campinas, de 1 a 15 de outubro de 1949. (2 ) A autora expressa os seus agradecimentos ao engenheiro agrônomo Antônio José Teixeira Mendes pela orientação dada na execução dêste trabalho. )
Engenheiro agrônomo, Secção de Citologia, Instituto Agronômico de Campinas
SUMMARY
Only one plant of Coffea arabica L. var. rugosa K.M.C., is available for study Its fruit production is very low. Of the progeny observed, none has reproduced th rugose condition of the leaves characteristic of the parent plant. Previous study ha shown that the rugose condition of the leaves could not be considered a somatic chimer because the tissues have a normal number (2n=44) of chromosomes.
The present cytological study was undertaken in order to find out if the low yiel of the rugose variety could be related to abnormalities in microsporogenesis.
The structure of the chromosomes in early prophase is difficult to study. In diaki nesis two pairs and sometimes three pairs of chromosomes appear to be attached to th nucleolus. Also in diakinesis it is possible to locate the centromere in the chromosoni pairs and to count the chiasmata. It was observed that an average of 6.6 bivalent show one single chiasma, 12.3 bivalents show two chiamata and 3.0 bivalents shoM three chiasmata. The average total number of chiasmata per cell at this phase is o 40.0, while at metaphase this number is reduced to 34.7. The first division in the mi crospore is normal and the resulting two nuclei differ in size and also in the size o their nucleolus.
The polen grains are normal, giving 69% germination on a medium containinj 0,5% of agar and 15% of sucrose.
It is concluded that microsporogenesis is normal and would not appear to be relate< to the low production of fruits of the rugosa variety. The fact that none of the progen1 has reproduced the rugose condition might be due to the limited number of plants observed.
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LITERATURA CITADA
- 1. Medina, Dixier M. Observações citológicas em Coffea. XIII - Observaçõe preliminares em Coffea arabica L. var. rugosa K.M.C. Bragantia 9: 47-51. est 1. 1949.
Datas de Publicação
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Publicação nesta coleção
31 Maio 2010 -
Data do Fascículo
Fev 1950
