Investigation of malformation symptoms in (Searsia lancea)

[摘要] English: The common karee (Searsia lancea, Anacardiaceae) is a common, widely distributed tree in South Africa. Popular as a garden and street ornament, its fruit and foliage serve as a source of food for many animals and humans. It also has applications inthe leather tanning industry and phytoremediation. Disease symptoms on S. lanceawere reported that resemble malformations of the closely related mango (Mangiferaindica, Anacardiaceae). This disease was named karee malformation disease(KMD). Formal investigation was conducted to determine whether malformationsymptoms on the two separate genera of the Anacardiaceae family share a causalagent, namely Fusarium spp. A pilot study and review of literature identified otherrelevant aspects worthy of study including insect associations, and differences inphytohormone and nutrient concentrations between healthy and affected trees. Itwas determined that Fusarium spp., which cause malformation of M. indica, does notcause malformation of S. lancea. It is also unlikely that the dominant fungal group,Alternaria alternata, causes S. lancea malformations. However, this study identifiedinteresting fungal and insect associations with healthy and malformed tissues of S.lancea. It is possible that the dominant insect group, namely Psyllidae, causesmalformations of S. lancea directly, or indirectly by acting as a vector of anotherpathogen. Lower concentrations of the phytohormones gibberelic acid and jasmonicacid, and higher concentrations of salicylic acid were noted in malformed comparedto healthy tissues of S. lancea. However, only the differences for salicylic acid weresignificant. Higher concentrations of the mineral nutrients nitrogen and potassiumwere noted for malformed tissues, while the phosphorus concentration was the samefor both conditions of S. lancea.

[发布机构] University of the Free State