Grouping Tolerant Level of Cocoa Genotypes Against Pod Rot Disease in Malaysia

Article Sidebar

PDF
Published
Aug 31, 2020
DOI
https://doi.org/10.22302/iccri.jur.pelitaperkebunan.v36i2.437

DIMENSION

ALTMETRIC

Main Article Content

Albert Ling Sheng Chang
Malaysian Cocoa Board, 5-7th Floor, Wisma SEDCO, Lorong Plaza Wawasan, Off Coastal Highway
Suhaida Salleh
Cocoa Research & Development Centre Jengka, Malaysian Cocoa Board, Jalan Jengka 23, P.O. Box 34, 28000 Temerloh, Pahang, Malaysia.
Nuraziawati Mat Yazik
Cocoa Research & Development Centre Bagan Datuk, Malaysian Cocoa Board, P.O. Box 30, Sg. Dulang Road, 36307 Sg. Sumun, Perak, Malaysia
Haya Ramba
Malaysian Cocoa Board, 5-7th Floor, Wisma SEDCO, Lorong Plaza Wawasan, Off Coastal Highway, Locked Bag 211, 88999 Kota Kinabalu, Sabah, Malaysia.
Ahmad Kamil Mohd Jaaffar
Malaysian Cocoa Board, 5-7th Floor, Wisma SEDCO, Lorong Plaza Wawasan, Off Coastal Highway, Locked Bag 211, 88999 Kota Kinabalu, Sabah, Malaysia.

Abstract

Cocoa pod rot disease (CPRD), caused by Phytophthora palmivora, is the main disease that caused major losses in Malaysia. It is important for screening the cocoa genotypes available in Malaysia for their tolerance level against the CPRD. This paper has an objective to select the potential genotypes tolerant to P. palmivora by grouping the cocoa genotypes available in Malaysia based on four tolerant levels such as tolerant, moderately tolerant, moderately susceptible and susceptible. The experiment was carried out at the laboratory of Plant Pathology at the Cocoa Development and Research Centre Jengka, Pahang using the detachedpod test. Isolate of P. palmivora was obtained from a naturally infected cocoa pod in cocoa field at the Cocoa Research and Development Centre Tawau, Sabah,Malaysia then inoculated by a single point on the ridges of pod to 40 mature unripe pods of each tested genotypes. Fifty genotypes were tested in this study.The assessed disease severity was the rate of lesion area development from 1 to 7 days after inoculation and the proportion of pod area infected by CPRD. Thedisease severity was significantly different among tested genotypes showing tolerance variability against CPRD. Four nonlinear models consisted of Monomolecularmodel, Exponential model, Logistic model and Gompertz model were used to fit the proportion pod infection area curve. The best fitted Gompertz model was used in calculated the area under disease progress curve (AUDPC). The variability of both disease severity variables was used to group the genotypes into four tolerant levels using the k-means clustering method with 10 genotypes in group I (torelant), 14 genotypes in group II (moderately tolerant), 13 genotypes in group III (moderately susceptible) and 13 genotypes in group IV(susceptible). Six genotypes in group I, namely MCBC 13, PBC 221, BAL 209, KKM 19, QH 1176 and KKM 22 were identified to have lower disease severity values compared to control tolerant genotype PBC 123 that could be suggested to the farmers to be planted in the field. 

Article Details


How to Cite
Ling Sheng Chang, A., Salleh, S., Mat Yazik, N., Ramba, H., & Mohd Jaaffar, A. K. (2020). Grouping Tolerant Level of Cocoa Genotypes Against Pod Rot Disease in Malaysia. Pelita Perkebunan (a Coffee and Cocoa Research Journal), 36(2), 139-153. https://doi.org/10.22302/iccri.jur.pelitaperkebunan.v36i2.437
Issue
Vol 36 No 2 (2020)
Section
Articles
Creative Commons License

This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

Authors who publish with this journal agree to the following terms:

    1. Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a Creative Commons Attribution License that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.
    1. Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.
    1. Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work (See The Effect of Open Access).

 

Author Biography

Albert Ling Sheng Chang, Malaysian Cocoa Board, 5-7th Floor, Wisma SEDCO, Lorong Plaza Wawasan, Off Coastal Highway

Cocoa pod rot disease (CPRD), caused by Phytophthora palmivora, isthe main disease that caused major losses in Malaysia. It is important for screening the cocoa genotypes available in Malaysia for their tolerance level against the CPRD. This paper has an objective to select the potential genotypes tolerant to P. palmivora by grouping the cocoa genotypes available in Malaysia based on four tolerant levels such as tolerant, moderately tolerant, moderately susceptible and susceptible. The experiment was carried out at the laboratory of Plant Pathologyat the Cocoa Development and Research Centre Jengka, Pahang using the detached pod test. Isolate of P. palmivora was obtained from a naturally infected cocoa pod in cocoa field at the Cocoa Research and Development Centre Tawau, Sabah, Malaysia then inoculated by a single point on the ridges of pod to 40 mature unripe pods of each tested genotypes. Fifty genotypes were tested in this study. The assessed disease severity was the rate of lesion area development from 1 to 7 days after inoculation and the proportion of pod area infected by CPRD. The disease severity was significantly different among tested genotypes showing tolerance variability against CPRD. Four nonlinear models consisted of Monomolecular model, Exponential model, Logistic model and Gompertz model were used to fit the proportion pod infection area curve. The best fitted Gompertz model was used in calculated the area under disease progress curve (AUDPC). The variability of both disease severity variables was used to group the genotypes into four tolerant levels using thin group I (torelant), 14 genotypes in group II (moderately tolerant), 13 genotypes in group III (moderately susceptible) and 13 genotypes in group IV (susceptible). Six genotypes in group I,  namely MCBC 13, PBC 221, BAL 209, KKM 19, QH 1176 and KKM 22 were identified to have lower disease severity values compared to control tolerant genotype PBC 123 that could be suggested to the farmers to be planted in the field.