Early-inbreeding depression in Vaccinium myrtillus and V-vitis-idaea

Fertility parameters were estimated in Vaccinium myrtillus and V. vitis-ida ea after self- and cross-pollinations performed in growth chamber. We showe d a drastic decrease in fertility after self-pollination as compared to cro ss-pollination. Number of plump seeds per berry was compared with previous field data. In both species, growth room conditions improved plump seed num ber after cross-pollination but not after self-pollination. In addition, in order to enhance resources supply to young developing fruits, cytokinin ap plication was tested in V. myrtillus but no effect was detected. We hypothe size that the partial self-sterility is due to inbreeding depression based on the expression of recessive lethals.