Author
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Turechek, William |
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Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/28/2012 Publication Date: 11/1/2012 Citation: Turechek, W. 2012. Spatial Distribution of Crown Gall in a Commercial Nursery of Weeping Fig. Plant Health Progress. doi:10.1094/php-2012-1126-01-rs. Interpretive Summary: Agrobacterium larrymoorei causes tumors on the trunk and branches of weeping fig (Ficus benjamina L.). The extent to which this pathogen is spread through the mother tree planting and transmitted to daughter branches during the process of propagation was studied in a commercial nursery in 2007 and 2008. The incidence of crown gall in the mother tree planting increased from 7% prior to propagation to nearly 32% eight months after the final round of propagation. Of the 4193 daughter branches monitored, 3.8% developed tumors. Statistical analysis indicated significant clustering of mother trees with tumors with within-row transmission being the predominant characteristic. Significant correlations between mother trees and daughter branches with symptoms of crown gall was also detected. Although pruning shears were routinely soaked in a quaternary ammonium-based disinfectant in this commercial nursery, the degree of sterilization achieved was apparently not sufficient to prevent transmission of the pathogen. Alternative sanitation measures should be sought and mother trees directly infected or neighboring infected mother trees should be avoided for propagation. This information is useful to nurseryman and scientists concerned with crown gall. Technical Abstract: Agrobacterium larrymoorei causes tumors on the trunk and branches of weeping fig (Ficus benjamina L.). The extent to which this pathogen is spread through the mother tree planting and transmitted to daughter branches during the process of propagation was studied in a commercial nursery in 2007 and 2008. The mother tree planting was scouted for tumors just prior to propagation and then again approximately 6-8 weeks after daughter branches were pruned from the mother tree. Branches selected for propagation were chosen from mother trees with no visible symptoms of crown gall and daughter branches were tagged and labeled to track disease development at approximately monthly intervals. The spatial distribution of mother trees with crown gall was characterized with runs, join-count and spatial autocorrelation analyses. The transmission of disease from the mother trees to the daughter branches was characterized with cross-correlation analysis. The incidence of crown gall in the mother tree planting increased from 7% prior to propagation to nearly 32% eight months after the final round of propagation. Of the 4193 daughter branches monitored, 3.8% developed tumors. Ordinary runs analysis indicated significant clustering of mother trees with tumors in both the 2007 and 2008 survey data, with within-row transmission being the predominant characteristic. Significant correlations between mother trees and daughter branches with symptoms of crown gall were detected out to two plants from the source. Although pruning shears were routinely soaked in a quaternary ammonium-based disinfectant in this commercial nursery, the degree of sterilization achieved was apparently not sufficient to prevent transmission of the pathogen. Alternative sanitation measures should be sought and mother trees directly infected or neighboring infected mother trees should be avoided for propagation. |
