Arbuscular mycorrhizas in southeastern Australian processing tomato farm soils
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Here we report the results of a study of the formation and functioning of AM in processing tomato farm soils from across southeastern Australia. In a survey, which included the majority of processing tomato producers in the industry, mycorrhizal colonization of roots was generally low, and in many instances, completely absent. This result can be explained by the use of soil fumigants on many farms. While previous cropping history did not explain levels of AM colonization, the proportion of mycorrhizal crops in the rotation had an influence on soil C, which was generally low across most sites. In an effort to further explore the functioning of AM, a targeted glasshouse experiment was undertaken, in which a mycorrhiza defective tomato mutant and its mycorrhizal wild-type progenitor were grown under uniform conditions. While AM colonization of plants was highest when grown in soil collected from an un-farmed site in this glasshouse experiment, AM provided a greater benefit (in terms of root Zn nutrition) when grown in soil collected from more fertile farm sites. Together, these data indicate that farm management decisions (in this case soil fumigation) may have consequences for the formation of AM, which in turn, may reduce the benefits of AM in these farm soils.
KeywordsArbuscular mycorrhizas Farm soil survey Glasshouse Mycorrhiza defective tomato mutant (rmc) Soil fumigation Tomato (Solanum lycopersicum L.)
The authors wish to thank the Australian Processing Tomato Research Council and its member growers for site access. We also gratefully acknowledge assistance provided by Ms Liz Mann and Dr Doris Blaesing in site selection and survey planning. Thanks also to Ms Leesa Hughes and Ms Merryn Smith for technical assistance. A small sub-set of the data presented here appear in preliminary form in the Australian Processing Tomato Research Council annual report (2009). This research was funded by the Department of Agriculture Forestry and Fisheries Caring for our County program, and with the support of the School of Biological Sciences, Monash University.
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