Fifty-one isolates representing the four Botrytis spp. associated with onion neck rot were cluste... more Fifty-one isolates representing the four Botrytis spp. associated with onion neck rot were clustered by unweighted pair group method with arithmetic mean based on universal-primed polymerase chain reaction (UP-PCR) fingerprints. Bootstrap analysis of the consensus phenogram clearly demonstrated five strong clusters among the four Botrytis spp.: B. cinerea (C), B. squamosa (S), B. byssoidea (B), and B. aclada (AI and AII). Subdivision of the 30 B. aclada isolates, AI (14) and AII (16), from Europe, Egypt, North America, and Japan was further supported by restriction analysis of the internal transcribed spacer of the ribosomal genes and spore size measurements. Gene diversities (H) among AI and AII isolates were very low (0.007 and 0.043, respectively). A likelihood ratio chi-square test (G2) of Nei's coefficient of genetic differentiation (GST) showed that both B. aclada subgroups, AI and AII, were significantly different from B. byssoidea (P < 0.001), and that B. aclada subgr...
Ulocladium atrum (isolates 385 and 302) consistently inhibited Botrytis aclada sporulation on dea... more Ulocladium atrum (isolates 385 and 302) consistently inhibited Botrytis aclada sporulation on dead onion leaf pieces under constant moist conditions and with an interrupted wetness period of 9 h. Clonostachys rosea (isolate 201) was as effective as U. atrum under constant moist conditions, but was ineffective if exposed to a drying period. No sporulation of B. aclada was observed 8 and 12 days after inoculation in the presence of U. atrum 302. C. rosea 201 significantly reduced B. aclada sporulation 8 days, but not 12 days after inoculation. When U. atrum 302 or C. rosea 201 was applied 1 day prior to B. aclada the antagonistic effect was higher compared to when the antagonists were applied on the same day. C. rosea 201 and U. atrum 302 did not obstruct the growth of B. aclada from necrotic onion leaf tips into living tissue, when artificially induced necrotic leaf tips were infested with B. aclada 24 h prior to antagonists. Three days after antagonist application, no symptoms could be observed on the healthy leaf tissue, nor was there sporulation on the necrotic leaf tip. However, B. aclada was immunologically detected 2 cm below the inoculation site. We conclude that under constant moist conditions the antagonists C. rosea 201 and U. atrum 302 cannot stop the progress of B. aclada from necrotic into fresh leaf tissue.
Five species of Botrytis are recognized as being associated with neck rot of onions: three of the... more Five species of Botrytis are recognized as being associated with neck rot of onions: three of them, B. aclada, B. byssoidea and B. allii, exclusively. Due to the difficulty of distinguishing them by morphological criteriaand lack of type material associated with B. aclada and B. allii, several synonomies have been proposed. We suggest that B. aclada and B. allii are both valid names. Species may be differentiated by conidial size, but the character is subtle, variable and there is some overlap. Both the smallest spored group (B. aclada) and the largest spored group (B. byssoidea) have 16 mitotic chromosomes, while the intermediate group (B. allii) has 32. Based on significant differences in Nei's coefficient of genetic differentiation derived from universally primed PCR (UP-PCR) fingerprints it was possible to recognize distinctions among the three exclusively neck rot-associated Botrytis spp. and B. cinerea and B. squamosa. Primers, designed from a sequence characterized UP-PCR...
In pursuit of a biological disease and stress management strategy for ornamentals, a three-factor... more In pursuit of a biological disease and stress management strategy for ornamentals, a three-factorial experiment was performed to examine the effects of plant darkness stress, Ulocladium atrum and Glomus mosseae on gray mold caused by Botrytis cinerea and plant vigour in potted roses. While darkness stress significantly enhanced gray mold, U. atrum negated the stress effect, reducing disease incidence to comparable levels in both stressed and non-stressed plants. G. mosseae interacted positively with U. atrum under non-stress conditions and negatively in darkness. G. mosseae significantly reduced non-specific leaf wilt incidence. Darkness significantly reduced the number of leaves formed above the pruning stub; U. atrum efficiently counteracted this effect, but had no effect under non-stress conditions. G. mosseae and U. atrum additively increased the total number of leaves per plant, and increased plant top dry weight. However, G. mosseae had no effect on dry weight under stress conditions. G. mosseae root colonization increased significantly when U. atrum was applied, but only under normal light conditions. In conclusion, a biological approach combining a foliar biocontrol agent and an arbuscular mycorrhizal fungus for gray mold protection seems promising.
Fifty-one isolates representing the four Botrytis spp. associated with onion neck rot were cluste... more Fifty-one isolates representing the four Botrytis spp. associated with onion neck rot were clustered by unweighted pair group method with arithmetic mean based on universal-primed polymerase chain reaction (UP-PCR) fingerprints. Bootstrap analysis of the consensus phenogram clearly demonstrated five strong clusters among the four Botrytis spp.: B. cinerea (C), B. squamosa (S), B. byssoidea (B), and B. aclada (AI and AII). Subdivision of the 30 B. aclada isolates, AI (14) and AII (16), from Europe, Egypt, North America, and Japan was further supported by restriction analysis of the internal transcribed spacer of the ribosomal genes and spore size measurements. Gene diversities (H) among AI and AII isolates were very low (0.007 and 0.043, respectively). A likelihood ratio chi-square test (G2) of Nei's coefficient of genetic differentiation (GST) showed that both B. aclada subgroups, AI and AII, were significantly different from B. byssoidea (P < 0.001), and that B. aclada subgr...
Ulocladium atrum (isolates 385 and 302) consistently inhibited Botrytis aclada sporulation on dea... more Ulocladium atrum (isolates 385 and 302) consistently inhibited Botrytis aclada sporulation on dead onion leaf pieces under constant moist conditions and with an interrupted wetness period of 9 h. Clonostachys rosea (isolate 201) was as effective as U. atrum under constant moist conditions, but was ineffective if exposed to a drying period. No sporulation of B. aclada was observed 8 and 12 days after inoculation in the presence of U. atrum 302. C. rosea 201 significantly reduced B. aclada sporulation 8 days, but not 12 days after inoculation. When U. atrum 302 or C. rosea 201 was applied 1 day prior to B. aclada the antagonistic effect was higher compared to when the antagonists were applied on the same day. C. rosea 201 and U. atrum 302 did not obstruct the growth of B. aclada from necrotic onion leaf tips into living tissue, when artificially induced necrotic leaf tips were infested with B. aclada 24 h prior to antagonists. Three days after antagonist application, no symptoms could be observed on the healthy leaf tissue, nor was there sporulation on the necrotic leaf tip. However, B. aclada was immunologically detected 2 cm below the inoculation site. We conclude that under constant moist conditions the antagonists C. rosea 201 and U. atrum 302 cannot stop the progress of B. aclada from necrotic into fresh leaf tissue.
Five species of Botrytis are recognized as being associated with neck rot of onions: three of the... more Five species of Botrytis are recognized as being associated with neck rot of onions: three of them, B. aclada, B. byssoidea and B. allii, exclusively. Due to the difficulty of distinguishing them by morphological criteriaand lack of type material associated with B. aclada and B. allii, several synonomies have been proposed. We suggest that B. aclada and B. allii are both valid names. Species may be differentiated by conidial size, but the character is subtle, variable and there is some overlap. Both the smallest spored group (B. aclada) and the largest spored group (B. byssoidea) have 16 mitotic chromosomes, while the intermediate group (B. allii) has 32. Based on significant differences in Nei's coefficient of genetic differentiation derived from universally primed PCR (UP-PCR) fingerprints it was possible to recognize distinctions among the three exclusively neck rot-associated Botrytis spp. and B. cinerea and B. squamosa. Primers, designed from a sequence characterized UP-PCR...
In pursuit of a biological disease and stress management strategy for ornamentals, a three-factor... more In pursuit of a biological disease and stress management strategy for ornamentals, a three-factorial experiment was performed to examine the effects of plant darkness stress, Ulocladium atrum and Glomus mosseae on gray mold caused by Botrytis cinerea and plant vigour in potted roses. While darkness stress significantly enhanced gray mold, U. atrum negated the stress effect, reducing disease incidence to comparable levels in both stressed and non-stressed plants. G. mosseae interacted positively with U. atrum under non-stress conditions and negatively in darkness. G. mosseae significantly reduced non-specific leaf wilt incidence. Darkness significantly reduced the number of leaves formed above the pruning stub; U. atrum efficiently counteracted this effect, but had no effect under non-stress conditions. G. mosseae and U. atrum additively increased the total number of leaves per plant, and increased plant top dry weight. However, G. mosseae had no effect on dry weight under stress conditions. G. mosseae root colonization increased significantly when U. atrum was applied, but only under normal light conditions. In conclusion, a biological approach combining a foliar biocontrol agent and an arbuscular mycorrhizal fungus for gray mold protection seems promising.
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