Chlorosis of Concord Grape Vines: Can We Relate Rooting-Zone Soil Microbial Community to Fe Availability?.

Many Concord grape (Vitis labrusca Bailey) vineyards in central Washington are faced with issues of leaf chlorosis that occurs around bloom. It significantly reduces vine size, vine uniformity and productivity, and even causes vine death. The yellowing of the leaves resembles classic iron (Fe) deficiency-induced chlorosis. Although significant progress has been made in documenting the occurrence of the problem in WA vineyards and its relationship with environmental factors, the exact cause of the problem remains unknown and no effective measures are currently available for growers to alleviate the problem. 

In this 1-year pilot study, we are taking a critical first look at the Fe-chelating capacity of the soil microbial communities associated with Concord vines suffering from chlorosis and comparing them to the communities of healthy vines.  We have identified five chlorotic/healthy paired sites within one organically-managed Concord vineyard in Prosser, WA, and sampled both soils and leaf tissues.  Soil microbial communities have been analyzed for total fungi and bacteria, as well as acid and siderophore production by selective and indicative media types.  We have also analyzed soil microbial community structure by T-RFLP, soil Fe bioavailability, and leaf tissue Fe status at two timepoints during the growing season.

We are actively working to identify microbial communities that may be beneficial to grape Fe nutrition and eventually provide a more sustainable and cost effective alternative to the application of synthetic Fe chelates.