Factors Affecting Germination and the Mode of Germination of Zygospores of Choanephora cucurbitarum

Abstract

Treatment of zygospores of Choanephora cucurbitarum with KMnO4, NaClO or HjO, effectively activated the spores and induced their germitiation. The optimum concentration of KMnO4 for activation of zygospores was 0.25 to 0.5%. Zygospores were not able to germinate in darkness even after activation by K!VlnO4. When zygospores from 40 to 50-day-old cultures were treated with 0.5% KMnO4 solution for 60 min before incubation on water agar at 24% under light, about 50% germinated in 10 days. KMnO4 treatment killed more than 99% of residual mycelial fragments, sporangiospores and sporangiola in the zygospore suspension. During germination disappearance of oil droplets in zygospores occurred prior to the cracking on zygospore wall. Both sporangial germination and mycelial germination were found. Moreover, sporangiole germination was observed for the first time. Zusammenfassung Faktoren, die die Keimung uod die Art der Keimung Ton Choanephora cttcurbitaram-Zygosforen beeinflussen Eine Behandlung von Choanephora eucurbitarum-Zygosporen mit KMnO4 NaClO bzw. H^O, aktivierte die Sporen und induzierte deren Keimung. Die optimale KMnO4-Konzentration ftlr die Zygosporenaktivierung lag zwischen 0,25 und 0,5%. In Dunkelheit fand eine Keimung der Zygosporen nicht statt, auch nicht nach einer KMnO4-Aktivierung. Wenn Zygosporen von 40 bis 50 Tage alten Kulturen mit einer 0,5%igen KMnO4-Losung fur 60 Minuten behandelt wurden und anschlieUend auf Wasseragar bei 24°C und mit Licht zur Keimung inkubiert wurden, keimten circa 50% der Sporen nach 10 Tagen. Die KMnHO4-Behandiung totete mehr als 99% der zurflckgebliebenden Myzelfragmente, Sporangiosporen und Sporangiolen in der Zygosporensuspension ab. Wahrend der Keimung verschwanden die in den Zygosporen vorhandenen Oltropfchen bevor die Zygosporenwand sich spaltete. Sowohi eine Sporangienals auch eine Myzelkeimung wurde beobachtet. AuBerdem wurde eine Sporangiolenkeimung zum ersten Mai nachgewiesen.

Choanephora rot of floral tops of Hyoscyamus muticus caused by Choanephora cucurbitarum

“…cucurbitarum causes fruit rots, and flower and leaf blights on a variety of plants including okra, squash, pumpkin, pepper, pea, bean, and cucumber (Yu and Ko 1997). Diseases caused by the pathogen in Japan have been recorded on pea, four o'clock, cabbage, cucumber, white h few-spored sporangium and sporangiophores, i fusiform sporangiospores with appendages, j chlamydospores in chains.…”

The inheritance of mating type and growth rate inChoanephora cucurbitarum

“…The zygospores retained on the 38-µm sieve were washed with tap water and resuspended in 20 mL of sterile distilled water. The suspension was mixed with an equal volume of freshly prepared 0.5% KMnO 4 solution (Yu and Ko 1997). After gently shaking for 30 min, zygospores were washed free of KMnO 4 on a 38-µm sieve with tap water.…”

“…Recently, an effective method was developed for zygospore germination of C. cucurbitarum (Yu and Ko 1997). A spontaneous slow-growing mutant of (+) mating type was obtained from sporangiospore cultures derived from a germinated zygospore of C. cucurbitarum.…”

“…& Rav. ) Thaxt is a plant pathogen causing fruit rots and flower and leaf blights on a variety of plants including okra, squash, pumpkin, pepper, pea, bean, and cucumber (Agrios 1988;Yu and Ko 1997). In nature and under culture conditions, the pathogen commonly produces multispored sporangia and unispored sporangiola.…”

“…This fungus is heterothallic and requires the presence of both (+) and (-) mating types for production of zygospores (Barnett and Lilly 1956;Wu and Chien 1980). Zygospores germinate after a dormancy by producing germ tubes with terminal germsporangia, germsporangiola, or develop directly into colonies (Yu and Ko 1997).…”