A NEW METHOD TO DETERMINE SELF-FERTILITY IN PLUM VARIETIES

The author has examined 16 self-fertile, 7 semi-self-fertile, 7 practically self-sterile and 19 fully self-sterile plum varieties. On the basis of the length of pistil /PL/, number of functional stamina /SN/, their ratio / SN/PL / and average length of internode /IL/ he found differences between the fertility groups. Pistils are the longest in semi-self-fertile, and somewhat shorter in self-fertile plum varieties; fully and practically self-sterile varieties are characterized by short pistils.

It is the other way round as regards the number of stamina: self-sterile plums have the largest number of stamina. The examination of varieties by group has confirmed that the SN/PL is suitable to characterize the extent of self-fertility: the ratio of semi-self-fertile varieties is lower than optimum / 1,88 pc./mm /, while in practically self-sterile and fully self-sterile plums the ratio ranges between 2,26 and 2,27 pc./mm, that is the relative stamen number /ratio/ higher than optimum.

The value of ratio is the numerical expression of sexual correlation. On the basis of 2940 flowers there is a significant negative correlation between pistil length and stamen number. In a mid-summer surveying of shoots we found a correlation demonstrable at a 2 % level between the SN/PL value and average length of internode of each varieties together.

This relationship is of great importance for selection of plum varieties.