Understanding the causes of crumbly fruit in red raspberry

Project Summary: A condition known as crumbly fruit occurs to differing degrees in different raspberry varieties and  is an indication of partial failure in the physiological processes in fruit development. Raspberry fruits are formed from an aggregation of multiple fertilized ovaries each of which are referred to as a drupelet as they become fleshy. In the condition known as crumbly fruit, which has been linked with pollen abortion and embryo sac degeneration, druplets may be greatly enlarged if their number is greatly reduced or in the case of small reductions, cohere imperfectly so fruit readily crumbles when picked. The fruit is neither suitable for fresh market or freezing and is therefore unmarketable. The extent of the problem varies from season to season and under different environments. Recently some progress was made in determining that both genetic and environmental control affect the crumbly phenotype (Graham et al., 2015).  A location on LG 1, highly significant for determination of the ‘crumbly fruit’ syndrome in red raspberry, was identified which is robust across seasons and in different environments. This work now needs to progress to understand what the triggers for the condition are and how the crumbly phenotype arises leading to an improved test in the production of nuclear stock plants for entry into the UK certification scheme and knowledge for breeding less crumbly varieties. 

Benefits to Industry: This project is industry facing aiming to solve the issue of crumbly fruit that despite being assessed in the high health scheme still arises in cultivation in some seasons causing extensive losses. The project would benefit breeders as by understanding the triggers of the condition, breeding lines can be dveeloped that are more resiliant to environmental conditions. The project would also benefit growers again through understanding of the causes of the condition and the significamt environmental effects and being able to mitigate depending on what triggers are identified. Access to more resiliant variaties would also have industry benefit. In terms of academic benefits an understanding of the GxE control of fruit development in general will be determined.

In summary project benefits are:

• Stable varieties less prone to the crumbly fruit condition
• Improved testing in certification scheme
• Identification of progeny in breeding programmes.
• Reduction in loss due to crumbly fruit
• Greater knowledge of fruit development in general leading to more targeted breeding