Submitted to: Journal of Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 26, 2007
Publication Date: December 15, 2007
Citation: Schnell Ii, R.J., Kuhn, D.N., Brown, J.S., Tondo, C.T., Motamayor, J.C. 2007. Development of marker assisted selection program for cacao. Journal of Phytopathology. 97(12):1664-1669. Interpretive Summary: Cacao is a small tree native to the Amazon basin. The seeds of cacao, called beans, are produced in fruit, called pods, that grow on the major branches and stems of the mature plant. Cacao is grown in humid, lowland areas in the tropics and the beans are the source of chocolate and cocoa butter, used in the confectionary industry. Three fungal diseases of cacao cause serious losses and these are known as frosty pod, witches' broom and black pod. The USDA in collaboration with Mars, Inc. has established a breeding program to produce new cultivars of cacao with resistance to these three diseases and with good production and quality attributes. The most efficient way to breed trees is by using the new molecular genetic techniques to accelerate traditional breeding strategies. This process is known as Marker Assisted Selection (MAS) and this process is now being used in cacao. The ability to utilize MAS has enhanced our selection effort and is leading to the release of new improved cultivars.
Technical Abstract: Theobroma cacao L. is an understory tree from the Amazon basis whose beans are the basic component of cocoa and chocolate. Four main genetic groups of cacao are traditionally described: Criollo, Trinitario, and lower and upper Amazon Forastero. Production of cacao in tropical America has been severely affected by two fungal pathogens causing diseases known as witches' broom (WB) and frosty pod (FP). These, along with black pod (BP), were responsible for over 700 million USD in losses in 2001. Currently, WB and FP are confined to Central and South America; however, commercial populations in West Africa and South Asia are highly susceptible to both diseases. USDA-ARS and Mars Inc. have developed a Marker Assisted Selection (MAS) program. Quantitative Trait Loci (QTL) have been identified for resistance to WB and FP and these are being employed in MAS. The international MAS project is expected to produce new disease resistant cultivars by 2012.