Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 18, 1998
Publication Date: N/A
Interpretive Summary: Production of oranges, grapefruit, tangerines, lemons, and limes relies entirely upon grafted trees with genetically different rootstocks possessing disease resistance, adaptability to soil, and a favorable effect on fruit productivity. All currently available citrus rootstocks have genetic weaknesses that make them susceptible to some environmental hazards sor limit their productivity. Development of better rootstocks is a high priority for growers in all citrus producing regions of the U.S. The process of citrus rootstock development requires that numerous trees of each scion/rootstock combination be produced rapidly and efficiently in preparation for field trials. Methods of forcing rapid bud growth have been previously defined for some of the citrus rootstocks used in commercial production. However, the best methods to use in forcing bud growth on many new hybrid rootstocks have not been defined. This study shows that a treatment involving bending the rootstock shoot after budding provides dramatically better bud growth and survival than cutting off the rootstock shoot. The most important finding is that all 19 hybrid rootstocks included in the test responded best in all respects to the same bending treatment. This suggests that the same treatment can be effectively employed in propagating all new hybrid rootstocks with a similar citrus x trifoliate parentage. One consequence is that decisions about nursery propagation on new rootstocks are significantly simplified. The result is more rapid testing and release of improved hybrid citrus rootstocks.
Technical Abstract: Bending was compared to cutting-off for effectiveness in forcing growth of sweet orange and mandarin trees budded on Carrizo citrange, Swingle citrumelo, and 17 new rootstock hybrids. For both scions, percent scion buds growing at 12 weeks was more than twice as great for the bending treatment in comparison to the cut treatment. Similarly, shoot length was more than 14 times longer with the bending treatment for both scions. Tree survival and yield of usable trees at 35 weeks old were also significantly better for the bending treatment than for the cut treatment. There was an overwhelming advantage to using the bending treatment instead of cutting off in forcing of bud growth in propagating citrus trees for field testing of new hybrid rootstocks.