DEVELOPMENT OF CITRUS BLIGHT SYMPTOMS AND RECOVERY OF 'VALENCIA' ORANGE TREES IN SOLUTION CULTURE

WUTSCHER, H. K.

Abstract


Nine trees of 'Valencia' orange on rough lemon rootstock were grown in solution culture from July 1989 to September 1995. Until the end of August 1993, all trees grew in a commonly used mineral element solution. In September 1993, four trees were changed to 1:2 soil:water extract made by boiling the slurry for 20 minutes. The soil came from a blight-affected commercial grove. Five trees remained in the original mineral element solution. Late in 1993, these latter trees started to show dieback, loss of feeder roots, and defoliation. Leaf analysis for blight-specific proteins started to become positive in January 1994, and all five trees were positive in November 1994. Two of the five trees died in the spring of 1995. The three remaining trees were changed to soil extract in March 1995 and rapidly lost the visual blight symptoms. Over three sampling dates, two of the three trees gave weakly positive or negative reactions in protein tests. The trees grown in soil extract consistently tested negative until the last sampling in August 1995, when two trees tested positive and two weakly positive although they showed no visual symptoms of citrus blight.

Keywords


blight-specific proteins; solution ph; soil extract

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283