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Anthurium (Anthurium andraeanum L.), a native of Tropical America is a perennial
herbaceous plant commercially grown for its attractive coloured spathe and green shiny
foliage. These have great economic value in the global flower trade that led to the budding
of many urban and rural anthurium entrepreneurs in the countryside, particularly in the state
of Kerala. During the recent past, the cultivation of this high valued cut flower crop is
challenged by many biotic factors and the changes in climate scenario occurred recently
led to the emergence of various new pests and diseases. Hence the present study was
undertaken to identify and document the diseases affecting anthurium grown in the state of
Kerala and the characterization of associated pathogens.
Purposive sampling surveys were conducted in the anthurium cultivated locations
of six districts viz. Thrissur, Ernakulam, Palakkad, Malappuram, Kozhikode and Wayanad
during the period from October, 2020 to July, 2021. The incidence and severity of various
symptoms were assessed and collected the samples for further studies. Twelve leaf spots
(KMALS, PBALS, VFNLS, VCNLS1, VCNLS2, IJKLS, KKYLS, OKMLS, OLRLS,
TLRLS, TBMLS and NLBLS) two leaf blights (VFNLB and OLKLB), one root rot
(VCNRR), one wilt (MNTLW) four inflorescence rots (MNTSR, CKDSR, PNMSR and
ALVSR) and one mosaic symptom (VCNML) were collected during the survey. Among
the leaf spots, PBALS recorded the highest per cent disease severity (PDS) of 58.23
followed by NLBLS (46.66 %) and ALVSR recorded the highest severity of 32 per cent
among inflorescence rots.
Isolation and pathogenicity studies of the associated pathogens yielded 18 fungal
and two bacterial isolates. Symptomatology of these diseases were studied both under
natural and artificial conditions. The fungal pathogens were characterized and identified by
studying cultural and morphological characteristics. Based on these characters, leaf spot
pathogens were identified as Colletotrichum gloeosporioides, Lasiodiplodia theobromae,
Phoma sp., Phomopsis sp., Corynespora sp., Pestalotiopsis sp. and those causing
inflorescence rot as Colletotrichum gloeosporioides and Phomopsis sp. and root rot
pathogen as Phytopythium sp. and wilt pathogen as Fusarium sp. The bacterial isolates
causing leaf blight were identified as Xanthomonas sp. based on cultural, morphological
and biochemical characteristics. The viral like symptoms subjected to electron microscopy
revealed the absence of any virus particles.
PCR amplification of Internal Transcribed Spacer (ITS) region of the fungal
genome followed by sequencing and in silico analysis confirmed that the pathogen
associated with TBMLS as C. queenslandicum, VCNRR as Phytopythium vexans, IJKLS
as Diaporthe phaseolarum, KKYLS and OKMLS as Phomopsis heveicola, NLBLS as
Lasiodiplodia theobromae, TLRLS as Pseudopestalotiopsis thea, VCNLS2 and OLRLS as
Corynespora cassiicola, MNTLW as Fusarium fujikuroi. The pathogens associated with
KMALS, PBALS, VFNLS, MNTSR, PNMSR and ALVSR belong to Colletotrichum
gloeosporioides species complex. The bacterial isolates (VFNLB and OLKLB) were
confirmed as Xanthomonas axonopodis through the amplification of 16S rRNA region of
the genome followed by sequencing and in silico analysis.
An in vitro experiment was conducted to study the efficacy of fungicides and
biocontrol agents/bioformulations against major fungal pathogens. Fungicides viz.
propineb, difenoconazole, carbendazim 12 % + mancozeb 64 %, cymoxanil 8% +
mancozeb 64 % and Bordeaux mixture were highly effective against L. theobromae and
Colletotrichum sp. (PBALS) as it resulted in cent per cent inhibition of these two pathogens
at all the three doses. In the case of P. vexans, fungicides viz. propineb, azoxystrobin,
carbendazim 12 % + mancozeb 64 %, cymoxanil 8% + mancozeb 64 % and Bordeaux
mixture were found to be effective even at a lower dose. Among the three chemicals tested
against Xanthomonas axonopodis, maximum inhibition was recorded in the case of
streptocycline. Dual culture and filter paper disc method revealed that the biocontrol
agents/formulations viz. Trichoderma sp., PGPR-II and PGPM were effective against all
the tested fungal and bacterial pathogens. Pseudomonas fluorescens was found effective
against three fungal and the bacterial pathogen.