Bacterial blight, caused by Xylophilus ampelinus (PANAGOPOULUS) WILLEMS et al. is a destructive disease of grapevine (Vitis vinifera). Incubation of cuttings at 15 degrees C for three days under moist conditions significantly increased the number of isolated X. ampelinus colonies. This treatment facilitates the isolation of the pathogen from infected material from which it could previously not be isolated.

The Palaeoproterozoic Transvaal Supergroup in the northern Cape Province of South Africa hosts high grade (. 60% Fe) hematitic and specularitic iron and manganese mineralisation. The mineralisation is primarily exposed along the western margin or in the central part of a major interference fold structure known as the Maremane dome. The bulk of South Africa's iron ore production is currently provided by two active mines, Kumba Resources megaton Sishen iron ore mine on the northern end of the dome, and the smaller Assmang Beeshoek mine on the southern closure. The undeveloped Sishen South deposit, which contains,400 Mt of high-grade hematite ore, is located y9 km towards the southwest of Postmasburg. It forms a linear extension of the Beeshoek mine and as such contains comparable laminated, breccia and conglomeratic iron mineralisation. The Transvaal Supergroup sediments were deposited in two distinct faultcontrolled basins on the Archean Kaapvaal craton. Basement rocks in the western Griqualand West basin are formed by a carbonate platform sequence (Campbellrand Subgroup), which is overlain by a thick sequence of banded iron formation of the Asbesheuwels Subgroup. A major unconformity separates these rocks from the red-bed Gamagara Formation, which is correlated with the base of the Olifantshoek Supergroup. Diamictites and lavas of the Postmasburg Group have been thrust over these units from the west. The mineralisation process is related to regional scale supergene iron enrichment of Kuruman banded iron formations along the unconformity. During regional tectonism associated with the Kheis orogeny (2400-1700 Ma) the Maremane dome was uplifted, and the basal dolomite units thus exposed to erosion and karstification. The overlying banded iron formations collapsed into karst sinkhole structures where leaching of silica and enrichment of hematite occurred. Although the exact mechanism of the mineralising process remains unclear, karstification preserved components of the original concordant laminated and massive ores. These ores were subsequently eroded and deposited as conglomeratic and gritty ores down-dip of the Maremane dome in alluvial fan systems. A thin veneer of recent calcrete or Tertiary Kalahari clay beds masks the subsurface geology and most of the orebodies, thus ground geophysical gravity surveys proved excellent exploration tools to penetrate the surficial cover. These surveys were used extensively for delineation drilling and to deduce the subsurface geology and structural development of the area. Finally Sishen South orebodies were modelled with ModelVision software in an attempt to obtain an exploration template for the surrounding area.

A sensitive and specific assay was developed to detect bacterial blight of grapevine caused by Xylophilus ampelinus (Panagopoulos, 1969) comb. nov. in grapevine cuttings. The 16S−23S rDNA intergenic spacer region of X. ampelinus was sequenced and pathogen‐specific primers were designed from a region in the spacer between the tRNA (Ala) and the 23S genes. A nested PCR (n‐PCR) reaction was applied with a first‐stage PCR using universal primers within the ends of the 16S and 23S genes, followed by a second‐stage PCR with nested primers specific to the X. ampelinus spacer region. A 277‐bp fragment was amplified from 38 Xylophilus strains tested, but not from saprophytes associated with grapevine or phylogenetically related phytobacteria. The 277‐bp product was shown to be derived from the X. ampelinus spacer region by restriction with Dra I, Sau 3AI, Taq I and Msp I, Southern hybridization and genomic DNA dot blots. When the (n‐PCR) procedure was applied in the absence of nontarget DNA, the limit of detection was less than 10 colony‐forming units (CFU) per µL. The same number of X. ampelinus CFU could be detected in the presence of 1·5 × 105 CFU µL−1 of Erwinia herbicola cells using the n‐PCR procedure.