Resumo em Inglês:

This paper describes the methods used and presents an analysis of the results obtained from three years of study, to determine the separate and inter-related effects of various agents such as gravity, wind and insects, in the pollination of flowers of Coffea arabica L. Observations were made and data obtained from several thousands of normal and castrated flowers that were maintained under natural and controlled conditions. It has been found that the importance of gravity, wind, and insects in pollination of the flowers may vary appreciably in relation to local environmental influences. The data obtained, however, indicate certain trends that are of definitive interest. Based on the total number of ovules, it was found that in 1228 normal flowers observed, 62 percent produced seed. This value is believed to represent in general the percentage of fertilization that might be expected to occur naturally. In tests designed to exclude the influence of wind, insects, and gravity, it was found that an average of 24 percent fertilization (within flowers) occurred. In measuring the effects of the combined agents of wind, insects and gravity it was found that 18.5 - 32.7 percent fertilization occurred as a result of self-pollination and 4.1 to 5.2 percent was due to cross-pollination. Analysis of the data also show in all except one case, the percentage of fertilization resulting from self-pollination was higher than that from cross-pollination. These findings show the importance of self-pollination in Coffea arabica. The use of castrated flowers was particulary helpful in determining the maximum effect of each of the pollinating agents studied under isolated controlled conditions. The general analysis of all data indicates that in the case of self-pollinated normal flowers the influence of wind and insects are about equal and that the effect of gravity is relatively less and likely to be of variable importance. In the case of factors affecting cross-pollination of normal flowers, wind seemed to have the most important influence. Based on a study of several different samples with large numbers of seed harvested from normal flowers, it. was also found that the percentage of seed resulting from cross-pollination was 7.3 - 9.0%. This percentage range of 7.3 - 9.0 is comparable to that of 4.1 - 5.2 shown above, the latter percentage range being based on total ovules and the former on the total seed harvested. Again these data emphasize the relatively limited occurence of cross-pollination in C. arabica.

Resumo em Português:

Um cafeeiro muito rústico e altamente produtivo, encontrado em uma propriedade agrícola do Estado de São Paulo, revelou ser tetraplóide (2n=44). Neste particular êle se assemelha à espécie C. arabica ; porém, em sua auto-esterilidade, se aproxima das espécies diplóides (2n = 22) de café. Imaginou-se, a princípio, que se tratava de uma forma tetraplóide espontânea de C. liberica ou de C. Dewevrei. O estudo aqui apresentado, porém, conduz à conclusão de que se deve tratar de um híbrido entre C. arabica e C. Dewevrei. No estudo da microsporogênese verificou-se a formação de uni- e bivalentes e mais raramente de tri- e tetravalentes. Supondo que o complemento cromossômico desta planta seja constituído de 22 cromossômios arabica haplóides e 22 cromossômios Dewevrei diplóides, e sabendo-se que : a) os cromossômios de C. arabica num indivíduo di-haplóide (2n = 22) formam 0 a 6 bivalentes ; e b) os cromossômios de C. Dewevrei formam normalmente 11 bivalentes, infere-se que a planta em estudo deve apresentar 11 a 17 bivalentes. Os bivalentes encontrados mais comumente, na realidade, variavam de 12 a 16 e, portanto, dentro daqueles limites. Isto justifica a hipótese de se tratar de um híbrido entre C. arabica e C. Dewevrei. A distribuição anafásica dos cromossômios é irregular, havendo formação de grãos de pólen com n = 15 a 28 cromossômios ; mais frequentes, porém, (cêrca de 80%), são os grãos com n = 20 a 24. A determinação do número de cromossômios em híbridos desse cafeeiro com C. arabica (2n=44), C. Dewevrei (2n=22) e C. Dewevrei (2n=44), como fornecedores de pólen, mostrou que também da macrosporogênese resultam oosferas férteis com n=20 a 24 cromossômios. Cêrca de 31% dos grãos de pólen são estéreis. Se na macrosporogênese as mesmas anormalidades ocorrem, é de se esperar que muitos óvulos degenerem. Isto acontece realmente, havendo grande número de frutos sem sementes ou providos de uma única semente em vez de duas.

Resumo em Inglês:

A very vigorous and productive coffee plant found in a plantation in the State of São Paulo was studied and found to be a tetraploid (2n=44). In this respect it appeared to be similar to the species C. arabica but in its self-sterility it seemed to be more like the diploid types (2n=22) of coffee. It was at first thought that this plant could be a tetraploid form of a diploid species such as C. liberica, or C. Dewevrei. The study presented herein, however, reaches the conclusion that this coffee plant is more likely to be the result of hybridization between C. arabica and C. Dewevrei. In a study of microsporogenesis it was observed that uni - and bivalents and less frequently tri - and tetravalent chromosomes were formed. If one assumes that the somatic complement of this plant is made up of the 22 haploid arabica chromosomes plus the 22 diploid Dewevrei chromosomes, then it can be estimated that the arábica chromosomes will form 0 to 6 bivalents as is known from the study of a haploid plant of C. arabica ; and if the Dewevrei chromosomes form 11 bivalents, then in the micros-porocytes of the hybrid one would expect to find 11 to 17 bivalents ; in the present study we found most frequently 12 to 16 bivalents which is within these limits. This, then, supports the hypothesis that the plant studied is a hybrid between C. arabica and C. Dewevrei. Study has shown that anaphasic distribution of the chromosomes is irregular and that pollen grains are formed with n = 15 to 28 chromosomes; most frequently (ca. 80%) the grains have n = 20 to 24. Controlled hybrids were made using this plant as the mother tree and C. arabica (2n=44), C. Dewevrei (2n = 22) and C. Dewevrei (2n = 44), as sources of pollen. A study of the chromosome numbers in these hybrids showed that fertile eggs were formed with n = 20 to 24 chromosomes. In the plant studied approximately 31% of the pollen grains were observed to be sterile. It was also observed that some ovules do not develop and one frequently encounters empty or only-one-seeded fruits. It is suggested that the sterility of the ovule and pollen grains may be due to the same factors.

Resumo em Português:

Após fazer a revisão de alguns dos principais trabalhos sôbre a auto-esterilidade no gênero Coffea efetuados em Java, foram relatados, de modo resumido, os resultados das pesquisas genéticas e citológicas que estão sendo feitas com os exemplares da espécie C. canephora no Instituto Agronômico de Campinas. Êstes estudos têm por finalidade conhecer o grau e as causas da auto-esterilidade dessas plantas. As autopolinizações realizadas indicaram que êsses cafeeiros são, realmente, auto-estéreis. Dos cruzamentos feitos, cerca de 50% se mostraram compatíveis. Tanto a formação do saco embrionário como a do pólen são normais. Em meio artificial conveniente, o pólen apresenta cêrca de 55% de germinação, o que foi considerado suficiente para promover a fertilização nos cruzamentos feitos. Foram realizadas observações sôbre o crescimento do tubo polínico em estilos de flores polinizadas com pólen estranho, compatível, e polinizadas com o próprio pólen. Nos cruzamentos compatíveis, o crescimento do tubo polínico é normal. No segundo oaso notou-se que, após a germinação, o tubo polínico tem o crescimento paralisado, não ultrapassando a região das papilas estigmáticas. Esta pode ser considerada a explicação da auto-esterilidade nos exemplares de C. canephora estudados. O mecanismo genético que controla o crescimento dos tubos polínicos ainda não pôde ser estabelecido. Entretanto, pesquisas estão em prosseguimento no sentido de se verificar se se trata de um mecanismo genético semelhante ao encontrado no gênero Nicotiana.

Resumo em Inglês:

This paper presents a review of pertinent literature related to studies of self-sterility in the genus Coffea and reports the results of cytological and genetic studies carried out on the species C. canephora at the Instituto Agronômico, Campinas, Brasil. The objetive of the study was to determine the degree and causes of self-sterility in the species C. canephora. In tests involving a large number of self-pollinations in flowers of this species, all were self-sterile and formed, no seed. In tests of cross-pollinations involving C. canephora approximately 50 percent were effective in the formation of seed. Cytological studies showed that the formation of the embryo-sac and pollen grains in C. canephora can be considered normal. Likewise a study of the pollen of this species on artificial media under controlled conditions, showed 55 percent germination and this was considered sufficient to bring about fertilization. In contrast, the cytological investigations of self-pollinated flowers showed that the number of pollen grains that germinated was very small and of those that did germinate, the formed pollen-tube was short and did not extend beyond the stigmatic papillae. Observations on compatible cross-pollinations on C. canephora showed that a large number of pollen grains germinated and that usually there were several pollen-tubes within the style. However, the rate of growth of pollen-tubes in C. canephora was found to be much slower that in C. arabica. The present investigation has shown that in flowers of C. canephora there is a very high degree of self-sterility and this has been related to poor germination of the pollen grains and subsequent limitation in the development of pollen tubes.

Resumo em Inglês:

A type of leaf-roll has been noticed for many years in commercial tobacco plantings in the State of S. Paulo. Leaf-roll plants were supposed to be affected by a virus disease, but repeated attempts to transmit it by grafting, juice inoculation and by insect vectors failed consistently. Later studies showed that the leaf-roll condition is due to genetic factors and that probably more than a pair of recessive genes are involved in its transmission. Even after the genetic nature of the leaf-roll condition was definitely established, attempts were made to induce the leaf-roll condition in plants genetically normal by several methods : 1. Spraying their leaves with the juice from leaf-roll plants ; 2. Approach-grafting a leaf-roll scion onto a normal plant and vice-versa, following with defoliation, cutting back or shading of the normal graft component. This was done to stimulate translocation of the phloem contents from the leaf-roll scion or stock into the normal stock or scion respectively. It was thought that if leaf-roll were due to the genetically controlled production of a hormone-like substance, these treatments might induce the leaf-roll condition in plants genetically normal. The results, however, have been negative.

Resumo em Inglês:

The Coffea arabica L. variety rugosa has been characterized as having rugose or roughened leaves. However, progenies of this variety obtained from selfed and open pollinated flowers have not, as observed to date, produced plants with characteristic rugose or definitely roughened leaves. This lack of rugose leaves in the seedling progeny of the variety rugosa led to the present cytological investigation to determine whether rugose leaves might be due to differences in the polyploid nature of the component leaf layers. Chromosome counts were made in cells of tissue obtained from root tips of seedlings and from root tips from stem cuttings, and from very young leaf buds. Chromosomes were also counted in the microsporocytes and in the microspores. The results of the cytological observations indicate that in the plant tissues examined there was an average number of 44 chromosomes. The counting of chromosomes in the coffee leaf buds was difficult due to the small size of the chromosomes. Observations also showed that microsporogenesis in the variety rugosa was normal and that the microspores contained 22 chromosomes. The results of this investigation show that Coffea arabica L. var. rugosa is a tetraploid plant, as are several other varieties of C. arabica that have been studied. The cytological observations also show that the rugose or rough condition of the leaves is not due to the presence of tissue layers of different polyploid nature.

Resumo em Inglês:

The male of Dysdercus mendesi Bloete (1937) has 2n = 16 chromosomes : 14 autosomes and 2 sex-chromosomes. Details are presented on the morphology of these chromosomes of the somatic cells of embryonic tissue. The long pair of rod shaped chromosomes is the longest of the set, and they show a conspicuous sub-terminal constriction (supposed to be the centromere) and five other smaller constrictions. In most of the other chromosomes sub-terminally localized constriction (supposed also to be the centromere) can also be observed. Based on these observations it has been concluded that the chromosomes of D. mendesi are morphologically normal. Dicentric chromosomes in the somatic tissue of this species are absent and the hypothesis of existence of diffuse centromere is also excluded. All of the chromosomes appear to have a definitive localized centromere. Metaphase spermatogonial plates have been observed where all the chromosomes appear as short and thick rods, apparently attached end-to-end, by definite connections, and forming a ring-shaped chain. Sometimes one or two chromosomes were found inside a ring formed by the others, but always connected to one or two of the chromosomes of the ring. Chromosomes chains of varied shapes were also found in the metaphase plates. In anaphase the longitudinally split chromosomes of the rings attain a curved shape as they move to the poles, giving the impression that both their extremities are pulled to the poles. A new hypothesis is presented to explain why the normal chromosomes of D. mendesi, provided with one localized centromere, can attain the curved shape observed in the anaphase configurations. It is based on the existence of connections attaching the chromosomes by their extremities, from metaphase until anaphase, and giving origin to the chain configuration already mentioned. These chains of chromosomes behave in anaphase as one rather long chromosomes with several centromeres. The centromeres are pulled to the poles, but as the extremities of the chromosomes of the chain are attached to each other, they give the false impression that both extremities of the chromosomes are being pulled to the poles, as if the chromosomes were provided with two centromeres, or as if there were diffuse centromeres.

Resumo em Inglês:

The writers review previous concepts concerning the reaction of citrus plants to the tristeza disease. It is recognized that environmental factors such as temperature, humidity and light can influence plant reaction, but these are considered of relatively minor importance. Characteristics of the plant itself govern its reaction to the disease and among those, resistance to infection, ability to permit virus increase and tolerance or non-tolerance of tissues are considered most important. Tests using viruliferous oriental citrus aphids for inoculation of various citrus types budded over sour orange rootstocks (table 1 and 2) showed a correlation between susceptibility to infection and severity of symptoms. The sweet oranges proved to be the most susceptible to infection and showed severe disease symptoms. The Barão sweet orange appeared to be more susceptible than Valencia. The mandarins tended to show some resistance to infection, but when infected, severe symptoms developed. The tolerant tangelos (7) behaved similarly to sweet oranges : They were very susceptible to infection and showed severe symptoms. The non-tolerant tangelos, susceptible citranges (7) and grapefruits behaved more or less alike, and showed medium susceptibility to infection and moderately severe disease symptoms. Among the grapefruits, Leonardy was. observed to be relatively more susceptible and showed more severe symptoms than Duncan. The pummelos, shaddocks and sour oranges were comparatively very resistant to infection and showed only moderate symptoms when infected. It has been found that the sour oranges can be more easily infected by tissue union than by the aphid vector. Poncirus trifoliata, citrumelos and resistant citranges showed no symptoms and no virus could be recovered from the inoculated plants even after three inoculations. The nature of injury caused by tristeza in the non-tolerant graft and intergraft combinations is discussed. The observation of symptoms shown by plants consisting of a sour orange inter-stem-graft between sweet orange roots and foliage seems to indicate that phloem collapse of the sour intergraft does not entirely prevent food translocation, since under field conditions the sweet stem below the sour intergraft continued, for almost two years, to increase in size at about the same rate as the sweet stem above. The growth of the sour intergraft was observed to be constricted and its lack of developments indicates a possible injurious effect of the disease on tissues other than the phloem. Root tissues of sour oranges have been found to be sensitive ;to injury, sincejsweet orange tops grafted directly onto sour orange roots and subsequently inoculated showed the usual tristeza symptoms. Death of rootlets and roots was found to occur not only in infected plants with tolerant tops and non-tolerant rootstocks but also on infected tolerant plants having an inter-stem-graft of non-tolerant sour orange. These observations and those made of root reaction on mechanically ringed plants indicate that although the root tissues of non-tolerant stocks may be sensitive to injury the rootlet and root symptoms are mostly secondary reactions. Tests carried out showed that the tristeza virus was recovered from insect protected sprouts grown at the ends of severed roots of Caipira sweet orange stock thus indicating that the virus was definitely present in the roots of a tolerant rootstock. Previously tristeza has been recognized as being associated with various citrus stock-scion combinations. In the present paper 50 seedling types have been reported as showing tristeza symptoms following heavy aphid inoculation. The symptoms shown by infected seedlings are similar to those shown by non-tolerant stock-scion combinations. Small sweet orange seedlings have been observed to show some symptoms of tristeza following heavy inoculations, but citrus types possessing tolerant tissues have shown a tendency toward recovery from symptom expression. The writers, on the basis of observed plant responses, have discussed the mode of inheritance of the main characteristis involved in plant reaction to tristeza. Some seedling progenies of known crosses between Poncirus trifoliata and sweet oranges (citranges) have been found to permit virus increase as the sweet orange parent does, whereas others behave like P. trifoliata and apparently do not permit virus multiplication. No relationship has been found between the trifoliata leaf-shape and inability to permit virus increase, since some of the hybrids that possess the trifoliata leaves, permit virus multiplication. Backcrosses of citranges to sweet oranges show a tendency to behave like the sweet orange parent. Hybrids between P. trifoliata and grapefruits (citrumelos) have behaved in most cases as the parent P. trifoliata. This seems to indicate that tolerant tissues and inability to permit virus increase are dependent on dominant factors in this type of cross. Hybrids between Citrus reticulata and C. paradisi (tangelos) do not show a clear-cut type of inheritance. Some tangelos behave Uke the mandarin parent, possessing tolerant tissues ; others behave like the grapefruit parent indicating possession of non-tolerant tissues. The inability to permit virus increase is a characteristic of little value in a rootstock improvement since tops of most commercial citrus varieties permit virus multiplication. It is pointed out that improvement of citrus rootstock with respect to tristeza should be aimed at combining tolerant tissues such as found in P. trifoliata or hybrids, C. sinensis, C. reticulata, etc., with other favorable characters such as vigor, resistance to gummosis, etc. Field tests showed that the reaction of infective buds on different rootstocks varies not only according to the tolerance of non-tolerance of the rootstock tissues, but also according to whether the buds themselves belong to types that possess non-tolerant or tolerant tissues. Infective buds of tolerant types, as sweet oranges, when budded on non-tolerant stocks produce a first flush of growth that is apparently healthy, but which later shows disease symptoms. For a period of about two months from date of budding, there is little or no difference between sprouts from healthy or infective buds of tolerant types. In contrast, when infective buds of non-tolerant types are budded on non-tolerant stocks, disease symptoms appear practically as soon as the buds start to grow. Observations indicate that infective buds from tolerant citrus types when budded on tolerant stocks usually do not develop symptoms even though the plant is a carrier of the virus. On the other hand observations indicate that infective buds of non-tolerant citrus types when budded on tolerant stocks may at times produce some symptoms. A possible explanation for the above-mentioned reactions is presented and is based on the relation between virus movement and food translocation in the plant. In the study of the relationship of tristeza virus to host tissues, plants composed of a sweet top over sour orange rootstock were allowed to develop two sweet orange branches. One branch of each plant was then ringed and inoculated by the vector. The branch not inoculated did not develop symptoms and 16 months after inoculation, buds were taken from the inoculated and the non-inoculated branches and tested for presence of virus. All buds taken from the inoculated ringed branches were found to be carrying the virus, whereas the buds taken from the other branch of the same plant did not have any virus. This experiment shows that the tristeza virus was not able to move across the ringed portion of the stem during that period, thus indicating that the tristeza virus is probably a phloem virus. Results from extensive buddings of various citrus stocks in the field indicate that buds taken from old sweet orange plants that have been known to be infected for a long time have been found to carry the virus in all buds. On the other hand, tests with buds taken from young plants recently infected, of Duncan grapefruit, sour orange and in some cases of Dancy tangerine and Valencia sweet orange, showed that not all buds were carrying the virus. It is not yet known whether buds that are mature prior to infection may temporarily escape virus invasion or whether citrus types which have non-tolerant tissues may limit to a certain extent complete systemic invasion of the tristeza virus.