A selective medium for improving quantitative isolation ofTrichoderma spp. from soil

ATrichoderma-selective agar medium (TSM) was developed for quantitative isolation ofTrichoderma spp. from soil. Selectivity was obtained by using chloramphenicol as a bacterial inhibitor, and pentachloronitrobenzene, p-dimethylaminobenzenediazo sodium sulfonate and rose-bengal as selective fungal inhibitors. The TSM also contains a low concentration of glucose which still allows relatively rapid growth and sporulation ofTrichoderma, enabling convenient and rapid identification ofTrichoderma colonies. All the 15Trichoderma isolates tested formed colonies and grew well on this medium. Recovery ofTrichoderma from artificially inoculated soils was high and was not affected by soil type or by other microorganisms. A positive correlation was observed betweenTrichoderma added to soil and counts ofTrichoderma colonies on TSM plates. When combined with a soil pellet sampler, the selective medium was also used successfully for recovery of the indigenousTrichoderma population of natural soils.     

Assumptions in tests for meiotic drive

Recent claims for the existence of meiotic drive in the ABO blood groups require the assumption of equal fertility (if there is no other selection operating) for the various mating types. There is evidence that does not support this assumption, and there are no convincing a priori grounds for making it.     

Shedding of the upper parts of grapevine shoots

Shedding of the upper parts of unlignified grapevine (Vitis vinifera L.) canes is frequent during autumn. Stress conditions during the growing-season lead to similar shedding of shoot tips. The separation process occurs above a node in the boundary area between the distal part of the diaphragm and the pith.Ethephon (2-chloroethyl-phosphonic acid) sprays, at 750 or 1500 mg l^?1, induced separation of the shoot tips of ‘Perlette’ and ‘Queen of the Vineyards’. Ethylene (C₂H₄) 200 vpm and ethephon at 10, 100 and 1000 mg l^?1 enhanced separation in shoot explants, whereas 2,4,5-TP (2,4,5-trichlorophenoxy-propionic acid) at concentrations above 1 mg l^?1 arrested it.This phenomenon may be regarded as a shoot abscission process which may represent adaptation of self-pruning of the grapevine.