Phenotyping of Vascular Streak Dieback Disease (Vsd) Resistant Cocoa Hybrids and Endorsement of Resistant Gene in Auspicious Genotype by Employing Molecular Marker Systems

Abstract

Cocoa (Theobroma cacao L.) is native to humid tropical region of Central America and considered as important agro forestry tree species. Vascular streak dieback (VSD), a devastating disease with distinct symptoms of dieback, is one of the major threats for cocoa cultivation. Th e confounding part of this disease is that chemicals have little effect on disease control. The most tenable and economic technique to tackle this disease is by evolving resistant materials. When this disease began to assume unmanageable magnitudes in India, Kerala Agricultural University had initiated VSD resistant breeding since 1995. Initially, 566 hybrids which expressed tolerance in the nursery for two years were field established. After fifteen years of field screening, 46 hybrids which manifested field resistance were selected for further study. Examination on self-incompatibility position exhibited that majority of them (37) were self incompatible. When yield contributing characters were accessed VSD I 31.8 was found to be superior and out rated the checks, most popular varieties available. Disease resistance was further confirmed by budding and molecular markers.VSD I 31.8 (CCRP 15) can be consider as a novel hybrid released in the world with VSD resistance and considerable yield.