Heat stress in raspberries, part 3

The final chapter in the raspberry heat stress story is about picking the right parents.  We have determined that some species of raspberry do better than others in the heat so we are using them in some of our crosses.

Above is a picture of 'Mandarin'.  This variety was released from NCSU in 1955. It is more resistant to heat than other varieties (note the other plots in the field behind it that are not doing as well). 'Mandarin' is 1/4 R. parvifolius, a species that is native to Asia. 

'Mandarin' is not available from nurseries, the fruit is small and soft and the yields are low, so it can not compete with newer varieties. However, we are using 'Mandarin' and some of its relatives in our program and are making progress in finding a heat tolerant variety with good fruit traits.