Investigation of malformation symptoms in (Searsia lancea)

Abstract

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 in the leather tanning industry and phytoremediation. Disease symptoms on S. lancea were reported that resemble malformations of the closely related mango (Mangifera indica, Anacardiaceae). This disease was named karee malformation disease (KMD). Formal investigation was conducted to determine whether malformation symptoms on the two separate genera of the Anacardiaceae family share a causal agent, namely Fusarium spp. A pilot study and review of literature identified other relevant aspects worthy of study including insect associations, and differences in phytohormone and nutrient concentrations between healthy and affected trees. It was determined that Fusarium spp., which cause malformation of M. indica, does not cause malformation of S. lancea. It is also unlikely that the dominant fungal group, Alternaria alternata, causes S. lancea malformations. However, this study identified interesting fungal and insect associations with healthy and malformed tissues of S. lancea. It is possible that the dominant insect group, namely Psyllidae, causes malformations of S. lancea directly, or indirectly by acting as a vector of another pathogen. Lower concentrations of the phytohormones gibberelic acid and jasmonic acid, and higher concentrations of salicylic acid were noted in malformed compared to healthy tissues of S. lancea. However, only the differences for salicylic acid were significant. Higher concentrations of the mineral nutrients nitrogen and potassium were noted for malformed tissues, while the phosphorus concentration was the same for both conditions of S. lancea.

Afrikaans: Die rooi karee (Searsia lancea, Anacardiaceae) is ‘n algemene, wyd verspreide boom in Suid Afrika. Dit is gewild as ‘n tuin en straat versiering, en die vrugte en loof dien as voedselbron vir verskeie diere asook mense. Dit het ook toepassings in die leerlooiery industrie en plant-remediëring. Siekte simptome op S. lancea was aangemeld en lyk baie soos misvormings van die na verwante mango (Mangifera indica, Anacardiaceae). Die siekte is kareemisvorming (KMD) genoem. ‘n Formele ondersoek was geloots om vas te stel of misvorming simptome op hierdie verskillende genera van die Anacardiaceae familie ‘n gemene oorsaak deel, naamlik Fusarium spp. ‘n Proefsteek en resensie van literatuur het ander relevante aspekte identifiseer wat die moeite werd is om te ondersoek, insluitend insek assosiasies en verskille in plant hormoon- en voedingstof konsentrasies tussen gesonde en misvormde bome. Dit was bevind dat Fusarium spp., wat misvormings van M. indica veroorsaak, nie misvormings van S. lancea veroorsaak nie. Dit is ook onwaarskynlik dat die dominante swam groep, Alternaria alternata, misvormings van S. lancea veroorsaak. Nieteenstaande het hierdie studie interessante swam en insek assosiasies met gesonde en misvormde weefsel van S. lancea identifiseer. Dit is moontlik dat die dominate insek groep, naamlik Psyllidae, misvormings van S. lancea direk, of indirek as ‘n vektor van ‘n ander patogeen, kan veroorsaak. Laer konsentrasies van plant hormone gibberelliensuur en jasmoonsuur, en hoër konsentrasies van salisiensuur was opgemerk in misvormde weefsel in vergelyking met gesonde weefsel van S. lancea. Slegs die verskille in salisiensuur was egter beduidend. Hoër konsentrasies van mineraal voedingstowwe stikstof en kalium was opgemerk in misvormde weefsel, terwyl fosfaatkonsentrasies dieselfde was vir beide kondisies van S. lancea.