Parental contribution analysis in hybrids bred for vascular streak dieback (VSD) disease resistance in cocoa
Loading...
Date
2016
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Vascular streak die back (VSD) disease caused by Oncobasidium theobromae (now renamed as Ceratobasidium theobromae), is
one of the major threats in cocoa growing countries, mainly because it cannot be controlled by any chemical application. In India,
since the disease outbreak in 1990, it has become an unmanageable problem of cocoa trees. Knowing the importance of resistant
hybrids for controlling this disease, Kerala Agricultural University took up resistant breeding programme. It was a massive
breeding programme which resulted in production of 5921 hybrid seedlings. After nursery screening of these hybrids by subjecting
to heavy inoculation load for more than two years from March 1996 to June 1998, only 566 seedlings survived and they were field
planted during June 1998. When relative efficiency of mother plants to transfer resistance to their progenies was estimated, it was
seen that G VI 126 (Scavina 6) showed maximum recovery of 32.6 per cent after fifteen years of screening. Comparison of
efficacy of male parents indicated that G VI 55 showed maximum recovery of resistant parents (168 nos.). During the entire
period of investigation, 267 hybrids were found free from the disease. Out of this, only 51 recorded satisfactory yield levels. All
these hybrids showed high value for selection differential (S) indicating maximum genetic gain.These hybrids can be used as
mother plants for establishing polyclonal garden, as VSD disease resistance is highly heritable and polygenically controlled. The
resistant hybrids identified (both high and low yield) can be utilized for further studies employing conventional and molecular
breeding methods.
Description
Keywords
Cocoa, disease resistance, pollination, selection differential, vascular streak dieback (VSD)
Citation
Journal of Plantation Crops, 2016, 44(1): 23-32