Abstract:
Leaf spot disease (LSD) is considered to be a major disease of cinnamon
(Cinnamomum verum J. Presl). Comprehensive information on temporal variation
of LSD is not available in Sri Lanka. A collection of forty cinnamon accessions,
established at Faculty of Agriculture, University of Ruhuna (UoR) from six major
cinnamon growing areas was used to determine the temporal variation of above
disease incidence (LSDI) during September, 2018 and December 2019, disease
severity (LSDS) and correlation between selected morphological characters and
LSDI. Using a disease assessment key, developed by Azad et al in 2019, the LSDS
was determined during 2019. The selected morphological characters of tree height
(Th), leaf length (LL), leaf width (LW), leaf length-width ratio (Ll/Lw) and petiole
length (Pl), bark thickness (Bth), trunk circumference (Tc) and twig diameter (Twd)
were recorded following the Descriptors for Cinnamon (Cinnamomum verum)
(Team of TURIS 2013 Project, 2016). All accessions reported 50 - 100% of LSDI in
both years. Mean LSDI (76.97) was low during 2018 with average monthly rainfall
(MRF) of 95.62 mm in contrast to that of 2019 (87.42) with 189.4 mm of MRF,
according to the Paired T test. Average values of LSDS of accessions collected from
Matara, Galle, Kalutara, Kurunegala, Ratnapura and Hambantota in the established
collection at UoR were 4.08, 3.30, 3.74, 2.00, 2.67 and 3.50 respectively during 2019.
Above values were different from those during the collection period of June, 2014
to April, 2015 (as 4.50, 4.82, 4.74, 4.60, 3.65 and 3.91 respectively). The accessions
were grouped into 3 clusters based on selected morphological characters at
rescaled distance of 60.25 in the cluster analysis. Morphological characters of the
accessions did not correlate with the LSDI. Above results indicate that LSDS is
variable among accessions. There is a temporal variation of LSDI among accessions
in the tested location.
