אסיף מאגר המחקר החקלאי

Oospore formation by Phytophthora infestans in potato tubers

Year:

2001

Source of publication :

Authors :

Volume :

91

Co-Authors:

Levin, A., Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel
Baider, A., Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel
Rubin, E., Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel
Gisi, U., Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel
Cohen, Y., Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel

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Abstract:

The ability of Phytophthora infestans, the causal agent of potato and tomato late blight, to produce oospores in potato tuber tissue was studied in the field and under laboratory conditions. In 1998 and 2000 field experiments, the canopy of potato cvs. Alpha and Mondial, respectively, were coinoculated with A1 + A2 sporangia of the fungus, and the infected tubers collected at harvest were examined for the presence of oospores. In 1998, only 2 of 90 infected tubers had oospores, whereas none of the 90 tubers examined in 2000 had any oospores. In the latter experiment, infected tubers kept in storage up to 12 weeks after harvest had no oospores. Artificial co-inoculations of whole tubers with A1 + A2 sporangia resulted only rarely in the formation of oospores inside the tubers. Co-inoculations of potato tuber discs taken from dormant tubers 0 to 16 weeks after harvest failed to support any oospore production, whereas discs taken from sprouting tubers of ≥18 weeks after harvest allowed oospores to form. Tuber discs showed enhanced oospore formation when treated before inoculation with either sugars, amino acids, casein hydrolysate, β-sitosterol, or chloroethylphosphonic acid. In contrast, reducing airflow into the petri dishes where potato tuber discs were incubated reduced the number of oospores produced. The number of oospores produced in tuber tissue was lower compared with that in leaf tissue regardless of the origin of isolates used. The data show that the ability of Phytophthora infestans to produce oospores in potato tuber tissue is very limited and increases with tuber aging.

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