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Coconut palm (Cocos nucifera), is a major and economically important plantation crop widely cultivated in Sri Lanka. A sudden outbreak of a rapidly spreading non-lethal syndrome was first reported in coconut palms from southern Sri Lanka in 2006. This syndrome was named Weligama coconut leaf wilt disease (WCLWD) as it occurred in the Weligama area. WCLWD symptoms are flaccidity and marginal necrosis of leaflets and intense yellowing of the fronds, similar to the Kerala wilt disease of coconut in India. As the disease progresses the crown becomes smaller, the trunk begins to taper and the palm becomes unproductive. Abiotic factors and extra-cellular pathogens were discarded as the cause of WCLWD. Considering that a phytoplasma was previously associated with Kerala wilt disease, the possible phytoplasma aetiology of WCLWD was investigated. DNA extracted from midribs of spear leaves was subjected to nested PCR with phytoplasma universal primers R16F2n/R16R2 and R16mF2/R16R2 nested with fU5/rU3; P1/P7 nested with Chrfor/rU3; and direct PCR with Pc399/P1694. PCR products of expected sizes were obtained from diseased but not from healthy palms from a disease-free area. The sequences generated from the PCR products were submitted to similarity search (BlastN) in the NCBI database which confirmed that a phytoplasma belonging to the 16SrXI 'Candidatus Phytoplasma oryzae' group is associated with WCLWD. The phytoplasma was found to be highly similar but not identical to Sugarcane white leaf phytoplasma (99%), Sugarcane grassy shoot phytoplasma (99%) and Kerala wilt phytoplasma (99%). [ABSTRACT FROM AUTHOR]

With the adverse effects of climate change, selecting the best tolerant varieties to drought stress is highly necessary to sustain the yield and productivity of agricultural crops including tree crops. However, classical drought tolerance selection studies of tree crops have several limitations due to their relatively long lifespan. In this study, we propose a method to identify stable high-yielding trees under changing soil moisture conditions using yield data of existing elite tree populations. We develop this method using the data from a tropical tree palm, Coconut ( Cocos nucifera L.) as a model crop. Our selection method considers individual palms as different genotypes. The method considered both mean trait values and their stability across different environments therefore, it can be effectively used to identify elite genotypes of tree crops for drought tolerance.•We propose an analysis framework to identify stable, high-yielding individuals of tree crops under limited soil moisture conditions using the data of existing tree populations.•Individual trees that produce stable and higher yields under soil moisture stress were identified based on mean yield and regression-based coefficient over different environments characterized by inter-annual rainfall variability.•Individual trees selected by this method can be used as parental populations in breeding programs that focus on developing drought-tolerant varieties., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Author(s).)