Gibberellin A₄Production bySphaceloma manihoticola,Causal Agent of Cassava Superelongation Disease

Abstract

The authors wish to thank F. Dennis for providing mass spectra of the esters of GA 1-GA 47 , T. Wachs of the Cornell Mass Spectrometry Service and T. Gianfania for their assistance with the mass spectrometry portion of the study. Further gratitude is extended to H. VanEtten and R. Millar for their thoughtful suggestions in reviewing this manuscript. Particular thanks are due S. V. Beer who generously provided space and equipment.

Cassava Superelongation Disease in the Caribbean

“…Early symptoms of the disease appear on expanding leaves, juvenile stems and floral tissues. Leaf spots are chlorotic and present as small, circular to irregular discolorations, approximately 0.5-5 mm in diameter, lightly colored and sometimes necrotic with a yellow halo [4,7,26]. Abundant spots may eventually deform the leaf causing sharp curvatures of one or more of the leaf lobes.…”

“…In the later stages of the disease, raised corky cankers appear as lesions on the petioles, leaf veins, and stems [5,7,13]. The stem cankers are usually hypertrophic which may coalesce to produce large elliptical to fusiform lesions [26] ( Figure 1). …”

“…The stem elongation observed is a result of the over production of Gibberellins, specifically gibberellin A4 (GA 4 ), produced by the fungus S. manihoticola [7,15,26,27]. …”

“…Fungal colonies are usually observed as a yellow mucoid mass but there may be other colors such as black and orange, all dependent on the strain and growth conditions [6,7]. Sphaceloma manihoticola has such variable colony morphology that Zeigler et al [26] considered this feature to be limited in its usefulness to distinguish species.…”

“…Cassava leaf agar supplemented with glucose generally produced a mixture of bright red, orange and black Cassavacolonies, while the same colonies on Czapek Dox agar (CZA) were uniformly orange in color and produced no aerial mycelium [13]. Another study on PDA showed colony color from nearly purely white through yellow to deep reddish purple and black [26].…”