Infectivity of Conidia of<i>Peronospora tabacina</i>After Freezing and Thawing

Cohen, Y.; Kuć, J.

doi:10.1094/pd-64-549

Cited by 8 publications

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“…The fact that oospores of Peronospora tabacina do not play an essential role in primary infection in southern Europe (CORESTA, 1961(CORESTA, , 1962 and Australia (Cruickshank, 1958(Cruickshank, , 1961(Cruickshank, , 1989 suggests that the asexual stage of the pathogen is very important in spreading the disease. Many studies (Hill, 1962;Krober, 1965;Cohen & Kuc, 1980;Cohen & Eyal, 1984;Gayed & Brow, 1984;Cruickshank, 1989) have indicated that sporangia of P . tabacina have very strong survivability and high dispersal potential, and thus take a very significant part in the epidemiology of tobacco blue mould.…”

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confidence: 99%

Viability test for Peronospora tabacina in stored Greek oriental tobacco

Zhang¹,

Qi³

et al. 1994

EPPO Bulletin

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During recent years, Peronospora tabacina has frequently been intercepted on leaves in lots of imported Greek oriental tobacco at ports of entry in China. The question arises whether such infected leaf debris can be a source of primary inoculum. The present study has examined the pre‐export viability of P. tabacina on stored Greek oriental tobacco. Firstly, basic experiments were done: (1) to find a suitable medium (2% Bacto (Difco) agar) for in vitro germination of P. tabacina sporangia; (2) to determine the optimum (15–21 °C), maximum (30°C) and minimum (2°C) temperatures for sporangial germination; (3) to devise a suitable method of inoculation for an infectivity test. Secondly, viability tests were done on stored Greek oriental tobacco harvested in 1986 and 1987. In vitro germination tests and infectivity tests were conducted separately, according to microscopic grading of the apparent turgidity of sporangia and sporangiophores collected from lesions of infected tobacco leaves of different cultivars and crop years. The tests were maintained for a much prolonged incubation period as compared with the controls. Neither in vitro germination nor infectivity tests showed any sporangia to be viable. Further work is needed to determine what period of storage is rationally acceptable for both plant quarantine and commercial trade.

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Section: Introductionmentioning

confidence: 99%

Viability test for Peronospora tabacina in stored Greek oriental tobacco

Zhang¹,

Qi³

et al. 1994

EPPO Bulletin

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Leaf surface chemicals fromNicotiana affecting germination ofPeronospora tabacina (adam) sporangia

et al. 1992

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A bioassay was used to evaluate the effects of cuticular leaf components, isolated fromN. tabacum, N. glutinosa (accessions 24 and 24a), and 23other Nicotiana species, on germinationof P. tabacina (blue mold). The leaf surface compounds includedα- andβ-4,8,13,-duvatriene-l,3-diols (DVT-diols), (13-E)-labda-13-ene-8α-,15-diol (labdenediol), (12-Z)-labda-12,14-diene-8α-ol (cis-abienol), (13-R)-labda-8,14-diene-13-ol (manool), 2-hydroxymanool, a mixture of (13-R)-labda-14-ene-8α,13-diol (sclareol), and (13-S)-labda-14-ene-8α,13-diol (episclareol), and various glucose and/or sucrose ester isolates. The above in acetone were applied onto leaf disks of the blue moldsusceptibleN. tabacum cv. TI 1406, which was then inoculated with blue mold sporangia. Estimated IC50 values (inhibitory concentration) were 3.0μg/cm(2) forα-DVT-diol, 2.9μ/cm(2) forβ-DVT-diol, 0.4μg/cm(2) for labdenediol and 4.7μg/cm(2) for the sclareol mixture. Manool, 2-hydroxymanool, andcis-abienol at application rates up to 30μg/cm(2) had little or no effect on sporangium germination. Glucose and/or sucrose ester isolates from the cuticular leaf extracts of 23Nicotiana species and three different fractions fromN. bigelovii were also evaluated for antimicrobial activity at a concentration of 30μg/cm(2). Germination was inhibited by >20% when exposed to sugar esters isolated fromN. acuminata, N. benthamiana, N. attenuata, N. clevelandii, andN. miersii, and accessions 10 and 12 ofN. bigelovii. These results imply that a number of compounds may influence resistance to blue mold in tobacco.

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