Effects of pre-sowing treatments on plant emergence and seedling vigour in true potato seed.

The influence of pre-sowing treatments in a solution of potassium nitrate and potassium phosphate (0.118 M KNO3 + 0.090 M K3PO4; K + K) at -1.0 MPa for 5 d, or in 1,500 mg l-1 gibberellic acid (GA3) for 1 d, on the characteristics of emergence and on seedling growth in 12 true potato seed (TPS) crosses was studied.The trials were carried out at two sites in Peru: La Molina and San Ramon. The latter site was characterised by having a higher maximum temperature and higher minimum and maximum relative air humidities. The nature of the TPS cross was the major factor determining seedling performance. Both pre-sowing treatments increased the percentage of emergence compared to untreated seed. These positive effects were most noticeable in TPS crosses characterised by having prolonged seed dormancy. At San Ramon, where the climatic conditions were less suitable for the germination of TPS, the effects of both pre-sowing treatments were more evident than at La Molina. The K + K pre-sowing treatment resulted in a shorter mean time for emergence and higher seedling vigour compared to the GA3 treatment. The ability of either pre-sowing treatment to improve the emergence and seedling vigour of TPS crosses characterised by having prolonged seed dormancy under high-temperature conditions may be of practical value for promoting TPS technology in tropical regions.