Identification and characterization of a novel cassava (Manihot esculenta Crantz) clone with high free sugar content and novel starch

Title 
Identification and characterization of a novel cassava (Manihot esculenta Crantz) clone with high free sugar content and novel starch 
Publication Type 
Journal Article 
Authors 
carvalhocastelo branco LJ, souza CRB, cascardomattos JC, Junior CB, Campos L 
Year of Publication 
2004 
Publisher 
Springer 
Place Published 
New York 
Volume 
56 
Journal 
Plant Molecular Biology 
Issue 
Pagination 
643 - 659 
Date Published 
11/2004 
ISSN 
1573-5028 
URL 
http://www.springerlink.com/content/h7769x33x5784x4t/ 
Keywords 
branching enzyme, Cassava, free sugar, novel starch 
DOI 
10.1007/s11103-004-4873-9 
Abstract 

This study reports the identification of a new class of cassava (Manihot esculenta Crantz) with a storage root showing unusual free sugar accumulation and novel starch. Twenty-seven clones high in free sugar were identified under cultivation in primitive rural community areas in the Amazon. Iodine test and glucose oxidase–peroxidase reagent strips were used, in the field, for identification of starch and glucose, respectively. Five out of these 27 clones of cassava were cultivated at EMBRAPA Genetic Resources and Biotechnology and used for biochemical characterization, starch synthesis enzyme activities and gene expression analysis. Carbohydrates were fractioned into free sugar, polymerized water-soluble and -insoluble α-polyglucan. Clones of series CAS36 accumulate over 100 times more free sugar (mainly glucose) than commercial varieties. Monosaccharide composition analysis revealed one clone with distinct water-soluble sugars not present in the commercial cultivar. Structure analysis of the water-soluble and -insoluble α-polyglucan revealed the presence of a glycogen-like starch in clone CAS36.1. This clone indicated disruption in the starch synthesis pathway for enzyme activities and protein blot analyses in ADPG-pyrophosphorylase and branching enzyme, and their corresponding protein. Gene expression analysis indicated the lack of transcript for the gene coding for branching enzyme, but not for the gene coding for the ADPG-pyrophosphorylase small subunit. In addition, the pattern of distribution of sugar and starch content showed to be related to tissue age in the storage root.

 
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