Several economically important diseases of forest trees and agricultural crops in many parts of the world have been linked to the ascomycete fungal pathogen Thielaviopsis paradoxa. This study compared the growth rate of 41 isolates of T. paradoxa sourced from different hosts and two countries (Nigeria and Papua New Guinea (PNG)) under six temperature levels (22 °C, 25 °C, 30 °C, 32 °C, 34 °C and 35 °C). Phylogenetic relationships were obtained from the analysis of their nuclear ribosomal DNA internal transcribed sequence (ITS) data. While all the isolates from PNG and few from Nigeria grew optimally between 22 °C and 32 °C, the majority had their highest growth rate (2.9 cm/day) between 25 °C and 32 °C. Growth performances were generally low between 34 °C and 35 °C; no isolate from the sugar cane grew at these high temperatures. The oil palm isolate DA029 was the most resilient, with the highest growth rate (0.97 cm/day) at 35 °C. Phylogenetic analysis delineated five clusters: a very large clade which accommodates the majority (30 Nigerian and 3 PNG oil palm isolates) and four small clades containing two members each. To a large extent, the clustering pattern failed to address the temperature–isolate relationship observed. However, only the four small clades represent isolates with similar temperature tolerances. It is most likely that wider and robust analyses with more diverse isolates and genetic markers will provide better insight on thermal resilience of T. paradoxa. Additionally, future research to establish relationships between vegetative growth at different temperatures and of different pathogenicity and disease epidemiology merits being explored. The results might provide useful information for the formulation of effective management and control strategies against the pathogen, especially in this era of climate change.

Purpose The oil palm could be prone to pest and diseases during its stages. One of the major diseases associated with the early stages of development of the oil palm is the Thielaviopsis diseases caused by the genus Thielaviopsis. This study was carried out in order to understand the mechanisms of interaction between the T. ethectica and the oil palm. Methods The plant metabolomics approach using the Gas chromatography mass spectrometry (GC-MS) was used to chemotype oil palm seedlings artificially infected with T. ethacetica and treated with water and fertilizer and those not treated. Results Gas chromatography mass spectrometry (GC-MS) analyses of the macerated centre spear of the treated and untreated oil palms fronds using n-hexane showed that the fatty acids, steroidal compounds and organic acids were more diverse in the untreated oil palm seedlings compared to the treated ones. Principal component analysis showed that the pathogen accounted for the diversity of the identified compounds. Conclusion The abundance of biosynthesized fatty acids and steroidal compounds in the untreated oil palms indicates their role in the oil palm defense mechanism thus also suggesting their possibilities as biomarkers for the early detection of T. ethecitica in the oil palm. Applying NPKMg for soil nutrient enhancement and water facilitated the reversal of the symptoms of T. ethecitica on the oil palm seedlings.