Location: Subtropical Plant Pathology Research2011 Annual Report
1a. Objectives (from AD-416)
Obj. 1: Identify available germplasm resistant to soilborne diseases and pests currently being controlled by pre-plant soil fumigation with methyl bromide for use as grafting rootstocks for Solanaceous vegetables, primarily tomato and pepper. Obj. 2: For selected rootstock germplasm shown to be effective for management of soilborne pests and pathogens of economic importance in the southeastern United States, describe rootstock-scion interactions that influence plant growth, fruit yield, fruit quality, and other important horticultural traits. Obj. 3: For selected rootstock-scion combinations shown to have an acceptable resistance to soilborne pests and pathogens and produce fruit of acceptable quality, evaluate under field conditions, similar to those used for commercial production, the plant growth, fruit yield, fruit quality, and other important horticultural traits that contribute to the economic feasibility of grafting.
1b. Approach (from AD-416)
Identify rootstock and scion germplasm material which have traits that resist diseases commonly found in the Southeastern U.S. currently controlled by methyl bromide. Screen available rootstock material for compatibility using current and new techniques. Select and evaluate rootstock and scion combinations for initial disease resistance and adaptation to current and new cultural technique. Determine the influence of rootstock/scion combinations on the horticultural characteristics of fruit including fruit appearance pre and post harvest quality, flavor, time to maturity, and yield. Develop techniques to evaluate the growth and development of the plant combinations under biotic and abiotic stress and evaluate grafted plant performance under varying cultural conditions.
3. Progress Report
Actual progress includes: 1) the determination of the ability of two important disease of tomato to be transmitted by cutting devices during the grafting process; 2) open field trials of 17 rootstocks for disease resistance and yield under conventional and organic farming practices; 3) determined the quality differences of grafted and ungrafted plants using analytical techniques; 4) continued investigation of resistance of pepper rootstocks to disease and nematode attack; 5) tested a number of grafting techniques to increase efficiency of survival for tomato; and 6) continued to test rearing techniques including environmental impact on grafted plant survival.
1. Tomato spotted wilt virus was found not to be transmitted by mechanical means through the cutting device. This was not true of Tobacco Mosaic Virus which was easily transmitted by a single razor cut to over 35 plants. This is an important finding in that the use of plants which have been exposed to the virus can easily be a source to inoculate many more plants in the grafting process. These experiments were repeated a number of times with the same results.
2. Field experiments with tomato rootstocks yield increases of yield up to 22% over the nongrafted controls. These increases in yield were also coupled with increases in overall plant vigor in some cases. These results were accomplished under organic growing conditions, without fumigation. Field results were confounded by three freezing events which completely eliminated the conventional field plots. Initial indications of resistance by some rootstocks in field experiments proved inadequate to stave off freezing damage with subsequent events with loss of the entire field.