Evaluation of dwarf coconut (Cocos nucifera L.) germplasm to the damage intensity caused by foliar diseases

Abstract

Coconut palm (Cocos nucifera L.) is a perennial crop with economic importance in Brazil. However, the culture is susceptible to several pathogens, such as Camarotella acrocomiae (large verrucosis), C. torrendiella (small verrucosis) and Botryosphaeria cocogena (leaf blight). These diseases reduce the leaf area of the plants. They usually occur as complex which are known as verrucosis leaf blight (CVLB). The objective of this study was to evaluate six accessions of dwarf coconut preserved in the active germplasm bank (AGB) of Embrapa Coastal Tablelands: BYD (Brazilian Yellow Dwarf Gramame), MYD (Malaysian Yellow Dwarf), CRD (Camaroonian Red Dwarf), BRD (Brazilian Red Dwarf Gramame), BGD (Brazilian Green Dwarf Jiqui), and MRD (Malaysian Red Dwarf). The study was carried out in a completely randomized block design with six treatments (accessions) and five replications (blocks), with 11 monthly evaluations from June 2015 to May 2016. The incidence and severity variables for the three diseases were evaluated. These six variables were jointly analyzed to describe the damage intensity. According to the non-metric multidimensional scaling ordination technique, most of the variability of the CVLB (72%) was associated with variations in damage caused by small verrucosis. A smaller portion of the variability (23%) was associated with the damage caused by large verrucosis and leaf blight, which in turn, were modulated by both the accessions and by the environmental variables. Interactions between the accessions and the seasonality of environmental conditions modulate the damage caused to dwarf coconut trees by the foliar diseases complex. These interactions, the duration of the occurrence and the magnitude of the differences between the accessions should be considered by the breeding programs.