|SCORSETTI, ANA CLARA - Institute Of Botany|
|JENSEN, ANNETTE BRUUN - University Of Copenhagen|
|LOPEZ LASTRA, CLAUDIA - Consejo Nacional De Investigaciones Científicas Y Técnicas(CONICET)|
Submitted to: Fungal Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2011
Publication Date: 11/17/2011
Citation: Scorsetti, A., Jensen, A., Lopez Lastra, C., Humber, R.A. 2011. First report of Pandora neoaphidis resting spore formation in vivo in aphid hosts under field conditions. Fungal Biology. doi:10.1016/j.funbio.2011.11.002.
Interpretive Summary: Most fungal pathogens of insects survive periods of extreme cold or dryness in the absence of their natural hosts by forming specialized, environmentally resistant structures. PANDORA NEOAPHIDIS may be the most common fungus affecting aphids worldwide but has never been known to produce the thick-walled resting spores typical by other members of the order Entomophthorales to which the fungus belongs. This paper provides the first molecularly and morphologically verified report that P. NEOAPHIDIS (which has been studied widely for 120 years) is able to produce resting spores in the field. This report opens new lines of research that might be used to determine whether resting spore production might be induced in experimental laboratory conditions, what conditions might be required to break the dormancy of mature resting spores, and to elicit their germination. New knowledge on this front would potentially increase the ability to use P. NEOAPHIDIS as a practical biological control agent in at least higher latitudes if cold winters prove to be necessary to the formation of these spores.
Technical Abstract: The entomopathogenic fungus PANDORA NEOAPHIDIS is a recognized pathogen of aphids, causing natural epizootics in aphid populations, and interacts favorably with aphid predators and parasitoids. Survival of entomophthoralean fungi in periods of unsuitable weather conditions or lack of appropriate host insects is accomplished mainly by thick-walled resting spores (zygospores or azygospores). However, resting spores are not known for some entomophthoralean species such as P. neoaphidis. Several hypotheses of P. NEOAPHIDIS winter survival can found in the literature but so far these hypotheses do not include the presence of resting spores. Resting spores were found in an aphid population where P. NEOAPHIDIS was the only entomophthoralean fungus observed during surveys conducted in organic horticultural crops in greenhouses and open fields in the Buenos Aires province, Argentina. The objective of this study was to confirm the P. NEOAPHIDIS affiliation of the resting spores found by molecular methods, to document and further describe these resting spores produced under natural field conditions. Microscopic characters and the ultrastructure of the double wall resting spores were described. The Argentinean resting spore isolates clustered together with P. NEOAPHIDIS isolates with bootstrap values above 98 percent in the SSU rRNA sequence analysis and with bootstrap values above 99 percent in the ITS II region sequence analysis. This study is the first molecularly verifiable proof that P. NEOAPHIDIS is able to produce resting spores in aphid hosts under natural conditions.