Effect of oxygen carbon di oxide and ethylene on growth sporulation and production of micro sclerotia by verticillium dahliae
Ioannou, N.; Schneider, R.W.; Grogan, R.G.
Phytopathology 67(5): 645-650
1977
ISSN/ISBN: 0031-949X Accession: 005258776
V. dahliae cultured in decreasing O2 (20.9-0.06%) and nearly constant CO2 (about 0.03%) concentrations, produced maximum radial growth and sporulation at 1.9 and 2.7% O2, respectively; growth was nil at 0.06% O2. The production of microsclerotia (MS) was maximum at 20.9% O2 and decreased progressively with each decrease in O2 concentration. Under constant O2 (17-18%) and increasing CO2 concentrations (ranging 0.03-20.9%), maximum radial growth and sporulation were produced at 6.2 and 0.03% CO2, respectively. In 20.9% CO2, radial growth was essentially the same as at 0.03%, but sporulation was reduced to about 20% of the maximum. The production of MS decreased with each increase in CO2 concentration and was completely inhibited at about 12.2% CO2. Under different mixtures of O2 and CO2, ranging from 20.9% O2 and 0.03% CO2 to 0.5% O2 and 20.5% CO2, radial growth was maximum at 16.5% O2 and 4.5% CO2, whereas conidia and MS production were maximum in normal air. Under 0.5% O2 and 20.5% CO2, radial growth was reduced to 17.5% of maximum and very few conidia were produced. The production of MS decreased progressively with each decrease in O2 and corresponding increase in CO2 concentration, and was completely inhibited at 10% O2 and 11% CO2. Infected tomato stems exposed to normal air, 10% O2 and 11% CO2, or 2.5% O2 and 20% CO2, produced the maximum, 10% of the maximum, and no MS, respectively. Infected stems, that were exposed to the inhibitory gas mixtures for 10 days, resumed production of MS after return to normal air, and produced within 10 days about 30-40% of the numbers of MS produced by stems exposed continuously to normal air. Exposure of cultures to ethylene concentrations ranging 0-35 .mu.l/l did not affect growth, sporulation, or MS production. Microsclerotia produced under the different atmospheres were equally viable. Also, MS produced under normal air, and then exposed to low O2 and high CO2 concentrations for up to 3 mo., survived as well as MS exposed continuously to normal air.