• Mycoplasma-like Organisms as the Causal Agent for Macrophylla Decline

      Taylor, Kathryn; Ellis, Danielle; Wright, Glenn (College of Agriculture, University of Arizona (Tucson, AZ), 1996-09)
      Previous literature concerning citrus and other tree crops led us to ask if there was molecular evidence for mycoplasma -like organisms (MLOs) as the causal agent of Macrophylla decline and two other decline diseases, citrus blight and lemon sieve tube necrosis. We had molecular probes available to us that were either specific for MLOs of tree diseases and others that were universal for all known types of MLOs. We used a polymerase chain reaction (MLO) to determine if MLOs were present in the vascular tissues of decline and healthy citrus. I all trials performed, the trees were negative for MLO-PCR products. In addition, we attempted to transmit putative MLO 's from decline affected trees to Vinca rosea MLO-nurse plants. We were unable to affect this type of transfer. In addition, our attempts to identify MLO's in phloem tissue gave us negative results. We have since revised our hypothesis. We are currently pursuing the hypothesis that these decline disorders are the result of a rootstock scion incompatibility, that we may be able to avoid culturally, while maintaining these valuable combinations.
    • Relationship of Viroids to Macrophylla Decline

      Taylor, Kathryn; Langham, Richard; Xiong, Zhongguo; Wright, Glenn (College of Agriculture, University of Arizona (Tucson, AZ), 1996-09)
      A physiological characterization has established that vascular changes in Macrophylla decline affected trees are not similar in character to xyloporosis affected trees. In addition, a survey of Macrophylla decline affected citrus did not establish any genetic similarity between Macrophylla decline and xyloporosis. We report diagnosis of either CCV or CEV by reverse transcription-polymerase chain reaction (RT-PCR), as well as diagnosis of Macrophylla decline or xyloporosis by Zn-distribution, water conductivity, accumulation of decline- specific proteins and examination of phloem morphology in lemon trees on the Macrophylla rootstock.