Morphology, membrane characterization and detection of a bacterium associated with ratoon stunting disease of sugarcane.
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Date
1984
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Abstract
Ratoon stunting disease (RSD) of sugarcane was first recognized in 1944
in Queensland, Australia (Steindl, 1961). The disease occurs worldwide
and causes significant yield losses, especially during drought. RSD
produces no external symptoms except a non-specific stunting (Steindl,
1961). RSD, which was first recorded 1n South Africa in 1953 (Anon., 1960),
causes a greater overall loss in yield than any other sugarcane disease
in South Africa. Yields of sugarcane are reduced by 20% to 40% and the
harvest of affected fields declines progressively with successive ratoons (Anon., 1980b). A virus was originally thought to cause RSD, but in 1973, a coryneform bacterium was implicated as the causal agent (Gillaspie et al., 1973; Teakle et al., 1973). In 1980, our laboratory reported the successful
isolation and culture of a coryneform bacterium associated with RSD of
sugarcane and was indicated to be the causal agent (Nayiager et al.,
1980). The lack of a rapid diagnostic technique applicable to mass screening of sugarcane has hindered progress in the control of the disease. There are two types of commonly used diagnostic tests. One test depends on the evaluation of internal stalk symptoms which may require from two to twenty six weeks to develop (Gillaspie et al., 1966; Matsuoka, 1971; Schexnayder, 1960; Singh, 1969). However, these symptoms are not
always present in RSD affected plants and similar symptoms can sometimes
result from other causes (Steindl, 1961). The other test involves
establishing the presence of the coryneform bacterium associated with
diseased plants. The bacterium is visible under high magnification by
phase-contrast microscopy (Gillaspie et al., 1973) or by electron microscopy
(Teakle et al., 1973). Although identification by the latter methods requires little time, the technology involved severely limits the number of samples that can be examined. Recently, serological techniques have been used (Brlansky et al., 1982; Damann et al., 1977; Davis et al., 1980; Gillaspie, 1978b; Gillaspie et al., 1979; Harris and Gillaspie, 1978) but their success has been limited. Besides problems with diagnosis of the disease, the precise morphology and taxonomy of the causal organism is unclarified.
The objectives of this research programme were, firstly, to characterize
the cultured intact bacterium and its constituent membranes both ultrastructurally and immunologically, and secondly, to evaluate various
immunological methods for detection of the bacterium. This study should
contribute to enhancing the taxonomic status of the bacterium and to the
use of a rapid diagnostic technique applicable to mass screening of
sugarcane. Such a technique should eventually contribute to effective
control of RSD.
Description
Thesis (M.Sc.)-University of Durban-Westville, 1984.
Keywords
Sugar-cane--Diseases and pests., Theses--Microbiology.