Decay Rates of Different mRNA in <Emphasis Type="Italic">E. coli</Emphasis> and Models of Decay

THE basis for messenger RNA instability in bacteria is not understood. Both functional capacity^1,2 and mass of messages for a given protein are lost at constant exponential rates which can differ, indicating independent processes³.     

Calcium and the plant cytoskeleton

Abstract. The regulation of the plant cytoskeleton by the concentration of free ionized Ca²⁺ in the cytosol is discussed. The effect is illustrated by considering the role of Ca²⁺ in regulating cytoplasmic streaming in Physarum and characean algae, and flagellar beating in Chlamydomonas . Examples are given of cytoskeletal processes in other plant cells that may be Ca²⁺ -regulated, together with an appraisal of some technical difficulties that currently limit their study.     

The effect of inoculating flowers and developing fruits with Botrytis cinerea on post-harvest grey mould of red raspberry

Raspberry flowers were inoculated in the glasshouse and field with dry conidia of Botrytis cinerea and the fruits derived from them subjected to post-harvest rot tests at c. 20°C and high humidity. Apparently healthy fully-ripe picked fruits derived from inoculated flowers developed grey mould faster than those from non-inoculated flowers in all tests. In the glasshouse experiments, fruits from inoculated tightly closed flower buds rotted more slowly than those from inoculated open flowers or those at later developmental stages. Fruits from inoculated whole flowers rotted more rapidly than those from emasculated flowers; the addition of pollen to emasculated flowers had little effect on post-harvest grey mould. In the dry summer of 1984 no fruits in the field from inoculated whole flowers rotted before ripening, but in the wet season of 1985 pre-harvest grey mould was common and the surviving healthy fruits rotted in c. 1 day after picking. Only minor differences were detected in host susceptibility to post-harvest grey mould in both glasshouse and field tests, the ranking of genotypes varied depending on whether or not flowers had been inoculated. The susceptibility of pistils of 40 Rubus genotypes to infection was examined 7 and 28 days after inoculation of stigmas with dry conidia. Conidia germinated on the stigmas and produced hyphae which grew through transmitting tissues of the styles to infect carpels symptomlessly in 17 red raspberries, one blackberry, two Rubus spp. and one hybrid. No germination occurred on stigmas of cv. Carnival and New York Selection 817.     

Effects of straddle-harvester design on cane blight (Leptosphaeria coniothyrium) of red raspberry

A new fruit catching device developed for raspberry straddle harvesters to reduce wounding of young canes and their consequent infection by Leptosphaeria coniothyrium was tested. During picking the young canes were contacted only by the foam rubber on a pair of belts which moved backwards along the harvester at the same speed that the machine advanced. The incidence of canes with cane blight lesions in 1981 was 18% following the use of the new device in 1980, and 79% following the use of a conventional commercial harvester equipped with overlapping metal fruit-catching plates. In comparison with the latter plates, the new device avoided wounding the cane surface directly: when the belt marks on these canes were inoculated with mycelium, however, the disease incidence was 77%. The new device caused wounds in 1980 by ripping leaves from nodes. In comparison with the commercial harvester the new device led to smaller lesions in 1981 and a lower percentage of canes dead above the fruit-catching zone. A modified new catching device tested in 1982 made barely detectable pressure marks on the young canes without bruising them. Only 6·6% of these canes developed vascular lesions after inoculation, an incidence similar to that for unwounded control canes (2·5%). The modified new device is advised for regions prone to cane blight where the cropping system has young and fruiting canes growing together.     

In vitro screening of coffee genotypes for resistance to coffee berry disease (Colletotrichum kahawae)

An in vitro protocol was developed to screen Coffea arabica genotypes for resistance to coffee berry disease caused by Colletotrichum kahawae. Initially, cultural conditions which influenced the growth of isolates of C. kahawae on agar media suitable for callus growth were determined. The growth of the fungus on the callus derived from susceptible and resistant genotypes was then assessed. This ensured that no detrimental competition for nutrients between the pathogen and the calli occurred. Optimisation of the concentration of the phytohormones added to the media, the temperature and incubation period were found to be important in the expression of differential responses of calli to inoculation with the pathogen as detected by measurement of hyphal growth. The screening of calli of nine C. arabica genotypes showed that this method identified genotypes highly resistant or susceptible to the disease and was sufficiently sensitive to distinguish those genotypes with moderate or low resistance.