Selection of clones for canopy replacement in rehabilitation of vascular streak diebak in mature cocoa (Theobroma cacao L.) in Malaysia

Vascular streak dieback (VSD) caused by the fungus Oncobasidium theobromae Talbot & Keane is a major disease of cocoa in Malaysia. In existing cocoa areas,canopy replacement using tolerant clones can be practiced for VSD control. The general objective of this study was to develop suitable canopy...

Full description

Saved in:

Bibliographic Details
Main Author:	Osman, Rozita
Format:	Thesis
Language:	English
Published:	2013
Subjects:	Plant canopies Cacao - Diseases and pests - Malaysia Fungal diseases of plants
Online Access:	http://psasir.upm.edu.my/id/eprint/41459/1/ITA%202013%201R.pdf
Tags:	Add Tag No Tags, Be the first to tag this record!

id	my-upm-ir.41459
record_format	uketd_dc
spelling	my-upm-ir.414592016-01-07T07:10:07Z Selection of clones for canopy replacement in rehabilitation of vascular streak diebak in mature cocoa (Theobroma cacao L.) in Malaysia 2013-05 Osman, Rozita Vascular streak dieback (VSD) caused by the fungus Oncobasidium theobromae Talbot & Keane is a major disease of cocoa in Malaysia. In existing cocoa areas,canopy replacement using tolerant clones can be practiced for VSD control. The general objective of this study was to develop suitable canopy replacement technique for rehabilitation of VSD infected mature cocoa. Screening of VSD tolerant clones were carried out on ten selected clones and non-grafted seedling was used as the control. Based on visual observations and biochemical analysis,four clones: PBC123, KKM25, MCBC1 and QH1003 showed tolerant to VSD. These clones were low in proline content (0.99 – 1.19 μmol g-1 fresh weight), low in total polyphenols content (1.42 – 1.72 mg GAE g-1 fresh weight) and high in peroxidase activity especially PBC123 (0.58 U mg protein-1) compared susceptible clones (proline content – 1.31 – 1.60 μmol g-1 fresh weight, total polyphenols content – 3.71 – 3.95 mg GAE g-1 fresh weight, peroxidase activity – 0.20 U mg protein-1). These clones were selected for subsequent study. The graft compatibility between PBC130 and selected clones was observed and evaluated. The observations and anatomical study of four clones revealed that four selected clones: KKM25, QH1003, PBC123 and MCBC1 were compatible to be grafted to PBC130 although it was already grafted to hybrid rootstock. The possible duration required for cocoa clones graft union formation was about 40 days. These four clones were subsequently used for study in the third experiment where they were grafted to mature PBC130 at four grafting distances and four grafting points under field conditions. The VSD DSI was higher (1.432) at 1.5m grafting distances, girth of the grafted branches was smallest in 2m grafting distance (8.73 cm) and 5 grafting points (9.49 cm), stomatal conductance was higher at 1.5 m grafting distance (47.24 mmol m-2s-1), proline content and peroxidase activity were higher at 1.0 m grafting distance (1.71 μmol g-1 fresh weight and 16.84 U mg protein-1, respectively) and total polyphenols content was higher at 1.5 m grafting distance. After successful canopy replacement,cocoa production yield had increased significantly (12.75 – 18.54 pods per tree per year) compared to before its implementation (5.50 – 10 pods per tree per year). After taking few factors into considerations, it was found that grafting at 1.5m grafting distance with 3 to 4 grafting points per tree can rehabilitated VSD infected mature cocoa trees and increase cocoa production. Plant canopies Cacao - Diseases and pests - Malaysia Fungal diseases of plants 2013-05 Thesis http://psasir.upm.edu.my/id/eprint/41459/ http://psasir.upm.edu.my/id/eprint/41459/1/ITA%202013%201R.pdf application/pdf en public phd doctoral Universiti Putra Malaysia Plant canopies Cacao - Diseases and pests - Malaysia Fungal diseases of plants
institution	Universiti Putra Malaysia
collection	PSAS Institutional Repository
language	English
topic	Plant canopies Cacao - Diseases and pests - Malaysia Fungal diseases of plants
spellingShingle	Plant canopies Cacao - Diseases and pests - Malaysia Fungal diseases of plants Osman, Rozita Selection of clones for canopy replacement in rehabilitation of vascular streak diebak in mature cocoa (Theobroma cacao L.) in Malaysia
description	Vascular streak dieback (VSD) caused by the fungus Oncobasidium theobromae Talbot & Keane is a major disease of cocoa in Malaysia. In existing cocoa areas,canopy replacement using tolerant clones can be practiced for VSD control. The general objective of this study was to develop suitable canopy replacement technique for rehabilitation of VSD infected mature cocoa. Screening of VSD tolerant clones were carried out on ten selected clones and non-grafted seedling was used as the control. Based on visual observations and biochemical analysis,four clones: PBC123, KKM25, MCBC1 and QH1003 showed tolerant to VSD. These clones were low in proline content (0.99 – 1.19 μmol g-1 fresh weight), low in total polyphenols content (1.42 – 1.72 mg GAE g-1 fresh weight) and high in peroxidase activity especially PBC123 (0.58 U mg protein-1) compared susceptible clones (proline content – 1.31 – 1.60 μmol g-1 fresh weight, total polyphenols content – 3.71 – 3.95 mg GAE g-1 fresh weight, peroxidase activity – 0.20 U mg protein-1). These clones were selected for subsequent study. The graft compatibility between PBC130 and selected clones was observed and evaluated. The observations and anatomical study of four clones revealed that four selected clones: KKM25, QH1003, PBC123 and MCBC1 were compatible to be grafted to PBC130 although it was already grafted to hybrid rootstock. The possible duration required for cocoa clones graft union formation was about 40 days. These four clones were subsequently used for study in the third experiment where they were grafted to mature PBC130 at four grafting distances and four grafting points under field conditions. The VSD DSI was higher (1.432) at 1.5m grafting distances, girth of the grafted branches was smallest in 2m grafting distance (8.73 cm) and 5 grafting points (9.49 cm), stomatal conductance was higher at 1.5 m grafting distance (47.24 mmol m-2s-1), proline content and peroxidase activity were higher at 1.0 m grafting distance (1.71 μmol g-1 fresh weight and 16.84 U mg protein-1, respectively) and total polyphenols content was higher at 1.5 m grafting distance. After successful canopy replacement,cocoa production yield had increased significantly (12.75 – 18.54 pods per tree per year) compared to before its implementation (5.50 – 10 pods per tree per year). After taking few factors into considerations, it was found that grafting at 1.5m grafting distance with 3 to 4 grafting points per tree can rehabilitated VSD infected mature cocoa trees and increase cocoa production.
format	Thesis
qualification_name	Doctor of Philosophy (PhD.)
qualification_level	Doctorate
author	Osman, Rozita
author_facet	Osman, Rozita
author_sort	Osman, Rozita
title	Selection of clones for canopy replacement in rehabilitation of vascular streak diebak in mature cocoa (Theobroma cacao L.) in Malaysia
title_short	Selection of clones for canopy replacement in rehabilitation of vascular streak diebak in mature cocoa (Theobroma cacao L.) in Malaysia
title_full	Selection of clones for canopy replacement in rehabilitation of vascular streak diebak in mature cocoa (Theobroma cacao L.) in Malaysia
title_fullStr	Selection of clones for canopy replacement in rehabilitation of vascular streak diebak in mature cocoa (Theobroma cacao L.) in Malaysia
title_full_unstemmed	Selection of clones for canopy replacement in rehabilitation of vascular streak diebak in mature cocoa (Theobroma cacao L.) in Malaysia
title_sort	selection of clones for canopy replacement in rehabilitation of vascular streak diebak in mature cocoa (theobroma cacao l.) in malaysia
granting_institution	Universiti Putra Malaysia
publishDate	2013
url	http://psasir.upm.edu.my/id/eprint/41459/1/ITA%202013%201R.pdf
_version_	1747811872890945536

Selection of clones for canopy replacement in rehabilitation of vascular streak diebak in mature cocoa (Theobroma cacao L.) in Malaysia

Similar Items