Morphological and molecular characterisations of Phytophthora palmivora infecting cocoa in Pahang and Perak, Malaysia

Phytophthora spp. are one of the most destructive plant pathogens worldwide. Many economically important crop species such as cocoa, rubber, jackfruit, durian, taro, papaya, pepper, coconut, potato, citrus and forest trees are susceptible to various diseases caused by Phytophthora spp. Agronomist...

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Main Author:	Alsultan, Wael M. K.
Format:	Thesis
Language:	English
Published:	2015
Subjects:	Cocoa - Diseases and pests - Malaysia Phytophthora palmivora - Case studies
Online Access:	http://psasir.upm.edu.my/id/eprint/68110/1/FP%202015%2092%20IR.pdf
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spelling	my-upm-ir.681102019-04-15T07:21:15Z Morphological and molecular characterisations of Phytophthora palmivora infecting cocoa in Pahang and Perak, Malaysia 2015-06 Alsultan, Wael M. K. Phytophthora spp. are one of the most destructive plant pathogens worldwide. Many economically important crop species such as cocoa, rubber, jackfruit, durian, taro, papaya, pepper, coconut, potato, citrus and forest trees are susceptible to various diseases caused by Phytophthora spp. Agronomists and plant pathologists have been aware of the economic importance of diseases caused by Phytophthora in Southeast Asia. However, there is a lack of published information on Phytophthora spp. in the tropics. Although many studies have been conducted over the past few decades to overcome diseases caused by Phytophthora spp., the general information is often not outlined with details while specific information of occurrence and economic impact are dispersed in many different publications in various languages. Black pod disease of cocoa caused by Phytophthora palmivora is a serious problem of economic importance to cocoa growers in Malaysia. It is also known to cause stem canker disease where their control in infected cocoa plantations is very difficult. This research was undertaken to study the cultural characteristics, reproduction, and pathogenicity as well as molecular characteristics of fourteen isolates of Phytophthora spp. randomly obtained from infected cocoa pods in two different states, Pahang and Perak in Peninsular Malaysia. The cultural characteristics of these isolates were assessed on four types of agar medium namely PDA , CA, VJA and CMA incubated at 25 ± 2°C showed various textures of colonies as fluffy with irregular margin on PDA, cottony with uniform margin on CA, slightly cottony with regular margin on VGA and flattish with regular margin on CMA. It did not show specific colony pattern on all four types of medium and each medium demonstrated its own morphological appearance. Growth rates of colonies were measured after three days of incubation on four types of agar media for one week and demonstrated that isolates grew significantly faster on CMA with 13.3mm/day, followed equally by VJA and CA with 10.0 and 10.2mm/day respectively, and the poorest growth was on PDA with 6.1mm/day. Dimensions of sporangia on CMA medium were measured averaging 43.48μm in length, 29.37 μm in width, 3.53 μm in pedicel length and 5.31 μm in size of exit pore. On culture media, the sporangia were of different shapes. Sporangia of isolates were all caducous. Zoospores were induced on four types of medium CA, VJA and CMA. Isolates on CA medium produced the largest number of zoospores than on VJA and CMA medium. Chlamydospores were produced on VJ broth ranging between 25.21 to 21.55 μm in diameter. Molecular identification using ITS region of rDNA confirmed that all isolates were Phytophthora palmivora. Eight isolates were selected randomly for pathogenicity tests on green healthy pods of KKM22 cocoa cultivar. The test results confirmed that isolates RB03 and RB04 from Pahang significantly more virulent with size of lesion 129mm and 117.75mm correspondingly compared to other isolates after five days of inoculation. Hence, complete brown to black lesions covered all inoculated after nine days. Cocoa - Diseases and pests - Malaysia Phytophthora palmivora - Case studies 2015-06 Thesis http://psasir.upm.edu.my/id/eprint/68110/ http://psasir.upm.edu.my/id/eprint/68110/1/FP%202015%2092%20IR.pdf text en public masters Universiti Putra Malaysia Cocoa - Diseases and pests - Malaysia Phytophthora palmivora - Case studies
institution	Universiti Putra Malaysia
collection	PSAS Institutional Repository
language	English
topic	Cocoa - Diseases and pests - Malaysia Phytophthora palmivora - Case studies
spellingShingle	Cocoa - Diseases and pests - Malaysia Phytophthora palmivora - Case studies Alsultan, Wael M. K. Morphological and molecular characterisations of Phytophthora palmivora infecting cocoa in Pahang and Perak, Malaysia
description	Phytophthora spp. are one of the most destructive plant pathogens worldwide. Many economically important crop species such as cocoa, rubber, jackfruit, durian, taro, papaya, pepper, coconut, potato, citrus and forest trees are susceptible to various diseases caused by Phytophthora spp. Agronomists and plant pathologists have been aware of the economic importance of diseases caused by Phytophthora in Southeast Asia. However, there is a lack of published information on Phytophthora spp. in the tropics. Although many studies have been conducted over the past few decades to overcome diseases caused by Phytophthora spp., the general information is often not outlined with details while specific information of occurrence and economic impact are dispersed in many different publications in various languages. Black pod disease of cocoa caused by Phytophthora palmivora is a serious problem of economic importance to cocoa growers in Malaysia. It is also known to cause stem canker disease where their control in infected cocoa plantations is very difficult. This research was undertaken to study the cultural characteristics, reproduction, and pathogenicity as well as molecular characteristics of fourteen isolates of Phytophthora spp. randomly obtained from infected cocoa pods in two different states, Pahang and Perak in Peninsular Malaysia. The cultural characteristics of these isolates were assessed on four types of agar medium namely PDA , CA, VJA and CMA incubated at 25 ± 2°C showed various textures of colonies as fluffy with irregular margin on PDA, cottony with uniform margin on CA, slightly cottony with regular margin on VGA and flattish with regular margin on CMA. It did not show specific colony pattern on all four types of medium and each medium demonstrated its own morphological appearance. Growth rates of colonies were measured after three days of incubation on four types of agar media for one week and demonstrated that isolates grew significantly faster on CMA with 13.3mm/day, followed equally by VJA and CA with 10.0 and 10.2mm/day respectively, and the poorest growth was on PDA with 6.1mm/day. Dimensions of sporangia on CMA medium were measured averaging 43.48μm in length, 29.37 μm in width, 3.53 μm in pedicel length and 5.31 μm in size of exit pore. On culture media, the sporangia were of different shapes. Sporangia of isolates were all caducous. Zoospores were induced on four types of medium CA, VJA and CMA. Isolates on CA medium produced the largest number of zoospores than on VJA and CMA medium. Chlamydospores were produced on VJ broth ranging between 25.21 to 21.55 μm in diameter. Molecular identification using ITS region of rDNA confirmed that all isolates were Phytophthora palmivora. Eight isolates were selected randomly for pathogenicity tests on green healthy pods of KKM22 cocoa cultivar. The test results confirmed that isolates RB03 and RB04 from Pahang significantly more virulent with size of lesion 129mm and 117.75mm correspondingly compared to other isolates after five days of inoculation. Hence, complete brown to black lesions covered all inoculated after nine days.
format	Thesis
qualification_level	Master's degree
author	Alsultan, Wael M. K.
author_facet	Alsultan, Wael M. K.
author_sort	Alsultan, Wael M. K.
title	Morphological and molecular characterisations of Phytophthora palmivora infecting cocoa in Pahang and Perak, Malaysia
title_short	Morphological and molecular characterisations of Phytophthora palmivora infecting cocoa in Pahang and Perak, Malaysia
title_full	Morphological and molecular characterisations of Phytophthora palmivora infecting cocoa in Pahang and Perak, Malaysia
title_fullStr	Morphological and molecular characterisations of Phytophthora palmivora infecting cocoa in Pahang and Perak, Malaysia
title_full_unstemmed	Morphological and molecular characterisations of Phytophthora palmivora infecting cocoa in Pahang and Perak, Malaysia
title_sort	morphological and molecular characterisations of phytophthora palmivora infecting cocoa in pahang and perak, malaysia
granting_institution	Universiti Putra Malaysia
publishDate	2015
url	http://psasir.upm.edu.my/id/eprint/68110/1/FP%202015%2092%20IR.pdf
_version_	1747812548795695104

Morphological and molecular characterisations of Phytophthora palmivora infecting cocoa in Pahang and Perak, Malaysia

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