2011 Annual Report
Parental rootstock lines with superior resistance to peach tree short life and Armillaria root rot as well as other desirable traits, are intercrossed to produce seedlings with the desired characteristics. Extensive testing is used to identify those hybrids which have the requisite combination of disease resistance and horticultural traits for successful commercial use.
Hand and bee pollinated crosses were made for the rootstock development program. New peach tree short life, Armillaria root rot, and horticultural trials were established at the Byron location. Previously established grower trials at other locations are continuing to be evaluated. New root-knot nematode trials were established at locations in GA and FL. New rootstock selections were made and propagated for further development. Advanced rootstocks selections nearing completion of evaluations were scaled up in anticipation of impending release(s).
Research on the chilling process in peach has shown that light affects completion of the chilling process. In addition, as chilling increases, the amount of heat to bring about bloom decreases in an exponential manner. In order to develop a model that can predict bloom in the variable southeastern climate, this chill-heat relationship will need to be taken into account. Such a model would be useful to the industry in allowing better management decisions based on a clearer understanding of the tree's progress to bloom.
This report documents research conducted under a Trust Agreement between ARS and the South Carolina Crop Improvement Association. The development of new rootstocks and management practices for the control of soilborne diseases and nematodes of peach is an urgent need of the southeastern US peach industry. This has become even more apparent with the introduction of Guardian peach rootstock in 1993. Guardian has been widely adopted by the southeastern US peach industry and though it has provided exceptional resistance to peach tree short life (PTSL), it is highly susceptible to Armillaria root rot (ARR) which has now surpassed PTSL as the primary cause of premature peach tree death. The first group of plum hybrid and plum x peach hybrid rootstock selections bred in this program have completed their disease resistance and horticultural evaluations. Several items stand out as potential candidates for industry use and one has been approved for release for commercial trial. Evaluations are continuing and the scaling up of materials to support expected release(s) is progressing.
Substantial progress was achieved in working out a clonal propagation protocol for MP-29 rootstock which will allow it to progress into large scale commercial production by the nurseries that have traditionally provided seed propagated trees to the southeastern peach industry.
Reighard, G.L., Beckman, T.G., Belding, R., Black, B., Byers, P., Cline, J., Cowgill, W., Godin, R., Johnson, R.S., Kamas, J. 2011. Six-year performance of 14 Prunus rootstocks at 11 sites in the 2001 NC-140 peach trial. Journal of American Pomological Society. 65:26-41.
Johnson, S., Anderson, R., Autio, W., Beckman, T.G., Black, B., Byers, P., Cline, J., Gonzalez, C., Cowgill, W., Godin, R. 2011. Performance of the 2002 NC-140 cooperative peach rootstock planting. Journal of American Pomological Society. 65:17-25. Okie, W.R., Blackburn, B. 2011. Interactive effects of light and chilling on peach flower and leaf budbreak. HortScience. 46(7):1056-1062.
Okie, W.R., Blackburn, B. 2011. Increasing chilling reduces heat requirement for floral budbreak in peach. HortScience. 46:245-252.