Microsporogênese, incompatibilidade e esterilidade masculina em Coffea congensis froehner

Abstract

O presente trabalho é um estudo da microsporogênese e do pólen de Coffea congensis: um estudo semelhante já foi apresentado sôbre Coffea canephora e C. Dewevrei, como parte de um conjunto de pesquisas para esclarecer a auto-incompatibilidade das espécies diplóides de café. A micrusporogênese é normal, cada microsporócito dando quatro micrósporos normais, com n=11 cromossomos. Os grãos de pólen são, em média, maiores do que os de C. Dewevrei e de C. canephora e menores do que os de C. arabica. Diversos cruzamentos e um grande número de autopolinizações foram efetuados, ficando evidente que a espécie Coffea congensis é auto-incompatível. O comportamento dos grãos de pólen quando postos a germinar em meio artificial ou em polinizações controladas, separa os grupos de plantas de Bangelan e de Uganda bem distintamente; o pólen destas plantas não produz tubo polínico, mas sempre expansões disformes, não apresentando nem 1% de germinação normal. Foram obtidos híbridos intra e inter-específícos com as plantas do grupo Bangelan usando-as como plantas-mães e como plantas fornecedoras de pólen. As plantas do grupo Uganda, entretanto, só produziram tais híbridos quando usadas como plantas-mães. Constataram-se, portanto, em C. congensis, dois fenômenos: a auto-incompatibilidade e a esterilidade masculina.

Microsporogenesis and the biosynthesis of floral small interfering RNAs in coffee have a unique pattern among eudicots, suggesting a sensitivity to climate changes

“…Cytogenetic analysis showed that microsporocytes in pre‐meiosis I, with cells in interphase (INT), appear in anthers of floral buds up to 1.5 mm (Figure 1a). In this stage, the nucleus (NC) and nucleolus (NO) are visible, reflecting the chromosome organization to duplicate and form chromatids (Conagin, 1961; Ma, 2005). The cells in meiosis were observed in anthers from floral buds of 1.5–4.2 mm (Figure 1b).…”

“…In prophase, chromosomes begin to condense and the nuclear envelope begins to disappear. In the cells in telophase, the last phase of meiosis, the chromosomes unwound and it is possible to see two nucleoli and the nuclear envelope reappears (Conagin, 1961; Ma, 2005).…”

Cytogenetics of coffee

“…rugosa to explain the low productivity of this variety and the lack of the wrinkled (rugosa) characteristic in the progenies of these plants. In addition to these varieties of C. arabica, similar analyses on microsporogenesis were made for several diploid species of Coffea, mainly those used in interspecific hybridizations with C. arabica Medina, 1952;Conagin, 1961;Medina and Rijo, 1969;Medina et al, 1977;Boaventura and Cruz, 1987). However, despite these studies on meiotic behavior, the characterization of individual chromosomes remained an important desideratum for progress with cytological research on coffee.…”

“…Although morphologically quite distinct, Coffea species present some common genetical features, such as the small variation in the chiasmata number (Mendes, A.J.T., 1950;Mendes C.H.T., 1950;Medina, 1950Medina, , 1952Conagin, 1961;Medina and Rijo, 1969;Medina et al, 1977) and the high frequency of bivalents in interspecific hybrids (Medina, 1972). Several studies have been carried out to establish precisely the relationships between species in the genus Coffea (Carvalho and Mônaco, 1967;Chinnappa, 1981;Lashermes et al, 1996Lashermes et al, , 1997, but interspecific relationships in this genus are still controversial since the affinities among species based on morphological characteristics and/or geographical distributions conflict with the relationships indicated by hybridizations and the cytological analyses of such hybrids (Carvalho and Mônaco, 1967;Medina 1972).…”

Identification of sources of male sterility in the Colombian Coffee Collection for the genetic improvement of Coffea arabica L.

“…In Coffea L., male sterility has been reported in diploid species [20,21], interspecific hybrids [22], and in the most economically important species, C. arabica [23,24]. In the latter, studies were carried out particularly on the germplasm from Ethiopia, the center of origin and diversity of the species.…”