Navegando por Autor "Costa, A. S."

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Clorose das folhas do cafeeiro excelsa
(Instituto Agronômico (IAC), 1951-07) Costa, A. S.; Mendes, J. E. Teixeira
A type of leaf chlorosis is shown by plants of excelsa coffee growing in nursery beds in a lath house at the Instituto Agronômico, Campinas. Tests made with various elements showed that this type of chlorosis is due to iron deficiency. Seedling plants of arabica coffee growing in the same beds do not show chlorosis, but these symptoms are exhibited by arabica scions grafted on some excelsa rootstocks. Scions from chlorotic excelsa plants recover the normal color when grafted on arabica rootstock. Likewise, arabica scions that had become chlorotic after being grafted on excelsa rootstock recovered when transferred onto an arabica rootstock. Other grafting tests indicated that no pathological cause seems to be associated with this type of chlorosis, and that it is probably due to genetical characteristics of the excelsa root system that prevents the plants from absorbing enough iron from the soil imder marginal conditions.
Estudos sobre a mancha aureolada do cafeeiro
(Instituto Agronômico (IAC), 1960-04) Costa, A. S.; Silva, Darcy Martins da
The widespread halo blight onslaught on young coffee plantings in 1955 and 1956 was not repeated in the following two years except in one or two instances. Plantings that had been severely affected in those years recovered naturally. The writers had difficulty in finding a few diseased leaves in many of them. Spraying tests with two antibiotics and 15 fungicides applied approximately every five days for four consecutive months did not offer any promise of control in a severely affected planting, although a slight favorable response was observed as a result of the application of two copper compounds. Treatments aimed at modifying the nutritional status of the plants did not induce any response in the way of increasing the coffee plant resistance against halo blight. A non-identified bacteria obtained from a bean planting that showed bean halo blight-like symptons was capable of inducing halo blight on coffee. Comparative inoculation tests showed, however, that the two disease-inducing agents were not identical. The bean bacteria induced halo blight symptoms on coffee leaves indistinguishable from those caused by the coffee bacteria, but the former organism was less pathogenic to coffee and more to bean than the latter.
Evidência electrono-microscópica de multiplicação dos vírus do mosaico do fumo e de vira-cabeça, em tecido foliar de cafeeiro
(Instituto Agronômico (IAC), 1970-08) Kitajima, E. W.; Costa, A. S.
Coffea plants (Coffea arabica L.) may be infected with vira-cabeça (Brazilian tomato spotted wilt) or tobacco mosaic (TMV) viruses, by mechanical means. Vira-cabeça virus (VCV) induces on leaves of ino- culated plants, chlorotic spots, resembling ringspot, while a virulent isolate of TMV causes chlorotic lesions with a necrotic center. In both cases, the viruses did not become systemic. Thin section profiles of leaf tissues obtained from the lesions caused by TMV or VCV were examined in the electron microscope. In cells from chlorotic lesions of TMV-inoculated coffea leaves, many cytoplasmic inclusions, with a fibrous aspect, were found. These inclusions were observed in epidermal, spongy and palisade parenchyma, but not in the vascular region. The rod-like particles, components of the inclusion are considered as TMV in situ. The fibrous inclusions were still identifiable, even in completely necrotic cells. X-body-like inclusions on the other hand, could not be seen. In cells from the lesion induced by VCV, spheroidal particles, iden- tified as those of the inoculated virus, were found mostly in epidermal cell. The particles were always within the endoplasmic reticulum elements. The finding of a large number of virus particles, in foliar tissue of coffea, infected by TMV or VCV, is considered as an evidence for the multiplication of these virus in the inoculated tissue, and supports previous pathological observations.
Infecção de cafeeiros com vírus de vira-cabeça
(Instituto Agronômico (IAC), 1960-03) Costa, A. S.; Silva, B. N.; Carvalho, Ana Maria B.
Coffee plants inoculated by rubbing with the tomato spotted wilt virus were highly resistant. Plants that were preconditioned in the dark for 4-8 days and inoculated in a similar manner developed concentric local lesions 10-25 days after inoculation. No systemic invasion of the plants followed. Recovery of the tomato spotted wilt virus from the lesions onto tobacco test plants was positive when the inoculum was prepared from lesions on coffee leaves 18 and 90 days after inoculation, but not after 210 days. When lesions from leaves that were showing the coffee ring spot disease were similarly treated and used to inoculate tobacco and other test plants no symptoms ensued, although these attempts were repeated a number ot times. This is considered evidence thot coffee ring spot is not caused by any of the common strains of the tomato spotted wilt virus complex used in the tests. Coffee plants exposed to a white fly population (Bemisia tabaci Genn.) bred on Sida micrantha plants affected with abutilan mosaic did not develop ring spot symptoms.