Heterokaryosis and Parasexuality in the Fungus Ascochyta Imperfecta

Abstract

The object of this investigation was to discover whether heterokaryosis and parasexuality occur in the imperfect fungus Ascochyta imperfecta. Both phenomena have been observed. The wild type of A. imperfecta grows on a minimal medium containing only salts plus a carbon source. Auxotrophic and morphological mutants have been isolated after treatment with ultraviolet light. When 2 different mutant auxotrophs are inoculated together onto minimal medium, colonies are consistently formed. These colonies might be due, a priori, to back‐mutation, diploidy, syntrophism or heterokaryosis. Back‐mutation and diploidy have been eliminated, since no back‐mutant nuclei have been isolated from any heterokaryon, and since the frequency of diploid nuclei is very low. The combination is primarily syntrophic (only 2% heterokaryotic hyphal tips) when the nicotinamide mutant is one component. The combination is primarily heterokaryotic (over 50% heterokaryotic hyphal tips) when both components are auxotrophs for amino acids. From the heterokaryotic hyphal tips, the 2 unaltered nuclear components have been isolated. Heterozygous diploid nuclei (4.2 X 10−‐7 per haploid nucleus) can be isolated from heterokaryons by plating, onto minimal medium, the primarily uninucleate conidia from a heterokaryon of 2 auxotrophs. The resulting colonies are isolated as potential diploids. Three properties of these isolates establish their diploid nature: (1) the isolates are wild type for nutrition and morphology; (2) their conidial length is uniformly greater than that of the haploids (1.21 times); (3) the isolates produce segregants with nonparental combinations of the marker genes. The diploid isolates are much more stable than heterokaryons. The recombinants from the diploids are still diploid, since (1) their conidial length falls in the diploid range, and (2) one of the recombinants has segregated a second‐order recombinant. Many of the expected classes of recombinants have not been detected.

Histone H3K9 and H3K27 methylation regulates fungal alkaloid biosynthesis in a fungal endophyte–plant symbiosis

“…Cultures of Escherichia coli were grown overnight in LB (Luria–Bertani) broth or on LB agar supplemented when necessary with either ampicillin (100 μg ml −1 ) or kanamycin (50 μg ml −1 ) as previously described (Miller, ). Cultures of E. festucae were grown on 2.4% (w/v) potato dextrose (PD) agar (Sanderson and Srb, ), under conditions previously described (Moon et al ., 1999; 2000). Liquid shake (200 r.p.m.)…”

Occurrence of fungicide resistance in populations of Botryotinia fuckeliana (Botrytis cinerea) on table grape and strawberry in southern Italy

“…Glucose potassium agar (GKA: 10 g of glucose, 2 g of K 2 HPO 4 , 2 g of KH 2 PO 4 ) was used to evaluate the response to SBI‐IIIs. Minimal medium [MM: 10 mL of solution A (10 g of KH 2 PO 4 , 100 mL of water), 10 mL of solution B (20 g of NaNO 3 , 5 g of KCl, 5 g of MgSO 4 · 7H 2 O, 0.1 g of FeSO 4 , 100 mL of water), 1 mL of micronutritive solution, 20 g of glucose] was used for APs. Acetate minimal medium (AcMM: MM without glucose, 5 g of sodium acetate, 0.01 M of citric acid, adjusted at pH 6.0 with KOH) was used for SDHIs.…”

Molecular characterisation and detection of resistance to succinate dehydrogenase inhibitor fungicides in Botryotinia fuckeliana (Botrytis cinerea)

“…The following media were used (ingredients per litre of distilled water; media were added with 20 g L −1 of agar Oxoid No. 3): malt extract agar (MEA) (20 g of Oxoid malt extract); potato dextrose agar (PDA) (infusion from 200 g of peeled and sliced potatoes kept at 60 °C for 1 h, 20 g of dextrose, adjusted to pH 6.5); acetate minimal medium (AcMM) [10 mL of solution A (10 g of KH 2 PO 4 , 100 mL −1 water), 10 mL of solution B (20 g of NaNO 3 , 5 g of KCl, 5 g of MgSO 4 · 7H 2 O, 0.1 g of FeSO 4 , 100 mL −1 water), 1 mL of micronutritive solution, 5 g of sodium acetate, 0.01 M of citric acid, adjusted to pH 6.0 with KOH], which is a medium enhancing toxicity of SDHI fungicides …”