Other pages about wound healing:
- The Process of Wound Healing
- Healing Factors
- Cutting Seed Tubers
- Handling Seed Pieces
- Wounding at Harvest
- Healing in Storage
Cutting whole potato tubers and use the pieces for seed ("seed-pieces") is a common practice in North America and Europe. To achieve high yields, nearly all harvested potato tubers are over six ounces and this is a key reason for cutting to produce seed-pieces to recommended planting size. However, another key reason is to overcome apical dominance exerted by the apical eye or sprout. In brief, the apical eye or sprout (at the "bud end") suppresses the sprouting of eyes more basal (toward the "stem end"). For more on apical dominance in seed tubers, see panel "Tuber Aging"). A major problem with cutting, however, is that it opens a severe and large wound through the skin allowing some key pathogens to get into the seed-piece. Because of this concern, seed-pieces must be allowed to heal (suberize) and seed treatments containing fungicides are applied.
First, how different is it to plant seed-pieces versus whole tubers? In a recent five-year study on Russet Burbank at the Univ. of Idaho (Nolte et al., 2003), whole seed ("single drop" "B") and seed-pieces, all weighing two to 2.5 oz as recommended, were exposed to Fusarium inoculum (the cause of dry rot). Seed-pieces were exposed to the inoculum before cutting. Some seed-pieces were treated with one of several fungicide dusts right after cutting. Whole tubers and seed-pieces were kept overnight at 64 deg F before planting. The latter would be referred to as "fresh cut" since wound healing would occur in the soil. There were significant differences in the amount of seed decay (Fusarium) and stem canker (Rhizoctonia) summarized in Figure 1. Whole tubers showed some seed decay suggesting some bruising during handling. Cutting tubers and treating them with a fungicide dust is better protection against dry rot and stem canker than whole tubers. [In Figure 1, the "cut, inoculated, treated" represents average data from inoculated seed-pieces with either mancozeb, Maxim or Tops MZ.] Cutting and treating tubers can improve also yields (Figure 2) further suggesting that treat seed-pieces work best.
Do seed-pieces perform better when healed in storage before planting? Studies at Michigan State Univ. (Chase et al., 1989) suggests that allowing cut seed to heal improved yields of Shepody and Yukon Gold (Figure 3). Fresh cut seed-pieces were planted on the same day as cut and compared to pre-cut seed-pieces which were cut two weeks before planting and stored at 60 deg F. The plants from pre-cut seed-pieces were also reported to emerge earlier, grow vigorously and have a higher stand.
Lastly, what amount of acceptable seed-pieces would one expect from whole tubers? Figure 4 shows the expected percent of seed-pieces weighing 1.5 to 3 oz cut from whole tubers. To get the most, good seed-pieces with the least waste, cutting tubers weighing about eight ounces was the most effective.
Chase, R.W., G.H. Silva, and R.B. Kitchen. 1989. Pre-cutting of seed potatoes. Amer J Potato Res 66:723-729.
Nolte, P., M. Bertram, M. Bateman, and C.S. McIntosh. 2003. Comparative effects of cut and treated seed tubers vs untreated whole seed tubers on seed decay, Rhizoctonia stem canker, growth, and yield of Russet Burbank potatoes. Amer J Potato Res 80:1-8.