Section 6
Chapter 5,318

Effects of osmotic potential on germination of micro sclerotia and growth of colonies of verticillium dahliae

Congly, H.; Hall, R.

Canadian Journal of Botany 54(11): 1214-1220


ISSN/ISBN: 0008-4026
Accession: 005317664

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The influence of available water, expressed as osmotic potential (.PSI.s), on germination of microsclerotia (MS) and expansion of colonies of V. dahliae was studied in osmotically adjusted aqueous and agar media. In distilled water (.PSI.s = 0 bar) at 25.degree. C, 64-70% of MS germinated within 36 h and the mean number of germ tubes per germinated MS (germination vigor) was 4.7. In aqueous solutions of KCl or NaCl, percentage germination and germination vigor were increasingly inhibited as .PSI.s was lowered, reaching 50% inhibition at -11 to -14 bar and 100% inhibition at < -98 bar. In aqueous sucrose solutions germination percentage and vigor were significantly higher (P = 0.05) than in salt solutions; minimum activity occurred at -4 bar, 50% inhibition occurred at -40 bar, and 100% inhibition occurred at < -114 bar. On corn meal dextrose agar (CMDA) amended with KCl, percentage germination at 25.degree. C was maximal at -9 bar, was reduced 50% at -40 bar, and was 0 at -90 bar. For a given .PSI.s, germination percentages at 25 and 30.degree. C were significantly greater than 20 and 15.degree. C. No germination occurred at 4 or 35.degree. C. Where .PSI.s was adjusted with KCl, agar media were less inhibitory to germination than aqueous media between 0 and -50 bar. On CMDA media amended with KCl, colony expansion was progressively faster as .PSI.s was lowered from -1.1 to -13 bar, then progressively slower as .PSI.s was lowered further. Rates of colony expansion at 20 and 25.degree. C were significantly greater than 4, 15 and 30.degree. C. At 25.degree. C growth was reduced 50% at -49 bar and was completely suppressed at -119 bar.

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