Selecting for Success: Good Things Come from Small Potatoes

Potato pollination produces true seeds which look just like tomato seeds. Each seed represents a genetically unique individual—and a potential new variety. Potato breeding programs sow these seeds into soil in pots and several months later harvest mini tubers—smaller tubers used as seed to grow potatoes in the field the following year. 

In the Cornell potato breeding program, potted plantlets are grown outdoors and organized by cross ID code within an area marked off by wooden planks. At harvest all the pots from one cross – typically two hundred pots per cross – are moved to the harvesting tables. On the table, the contents of each pot are emptied and a crew member sifts through the soil to find the mini tubers.  

Only four mini tubers are collected from each pot for the next stage in the breeding pipeline. If there are extra mini tubers, the largest is put in the “fifths bucket.” These extra tubers are sent to other breeding programs in the country to be evaluated in their programs.  

The four mini tubers are placed into a brown paper bag which is in turn put into a crate labeled with the cross-ID code. 

The soil on the table is swept onto a conveyor belt, which drops it into a truck to be taken away and composted. The crew members repeat this process for each pot until all pots for a cross have been processed. Notably, no selection is conducted at this point in the breeding pipeline since plant performance in pots is not highly predictive of performance in the field. 

At the end of the workday, the mini tubers are transported to 40°F cold storage. The mini tubers will stay in storage until the planting of four hill plots the following growing season.  

Article and Photos by Pia Spychalla