Environmental influence on physiological factors that determine seed quality is discussed in relation to true potato seed (TPS). This review has been motivated by the need for high quality seed for the proper evaluation of TPS technology. The objectives of tuber production may not be in harmony with those required for the production of high quality TPS. The production of high quality TPS may be influenced by the stronger sink strength ability of fast developing tubers for assimilation of available nutrients. Earliness of tuber formation, which is needed in TPS progenitors, may tend to result in incomplete TPS development. Limiting conditions during seed development decrease the potential of the seed for field establishment. Seed vigor is the most important attribute of seed quality since it is essential for seedling performance under the adverse conditions commonly encountered during field development. The attractiveness of TPS technology for tropical areas, where potato production is limited by low-quality seed tuber availability, is decreased by the lack of seedling vigor and uniformity of seedlings derived from TPS. Current research indicates that considerable genetic improvement of TPS vigor and uniformity is possible. It is suggested that significant immediate improvement of TPS quality would result from agronomic techniques that reflect understanding of the physiological factors that influence the production and maintenance of high quality seed. Research areas needed to develop methodologies for TPS production with optimum expression of genotype are identified.

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Freshly harvested, true potato (Solarium tuberosum L.) seeds (TPS) will germinate at 15 ± 5C, but because of dormancy they must be stored for ≈18 months before they will germinate at >25C. Effects of seed moisture content (SMC) and temperature in storage on germination and seedling emergence were periodically tested during 18 months for seeds harvested from three positions on the mother plant. Seeds were stored with 37.,5%, and 7% SMC (on a dry weight basis) at 5 and 45C; sublets were removed monthly (1 to 7 months) from 45C and stored at 5C. Seed dormancy and viability were best preserved in storage at low SMC and low temperature, Seeds stored at 45C and 3 % SMC progressively lost dormancy and, after 4 months of storage, germination was up to 88% after 4 days at 127C. This rate of germination decreased with further storage. Up to 100% emergence occurred in 9 days in seeds stored for 18 months at 45C and 3% SMC. Seeds stored at 45C and 5% SMC lost dormancy in 2 months and <50% emergence occurred after 18 months. Seeds stored at 45C and 7% SMC deteriorated and became nonviable within 6 months of storage. The position of seed development did not significantly affect seed size or weight. However, seeds produced from the bottom third of the plant (lot A) were the most vigorous after dormancy was released with sufficient storage. This suggests that efforts should be made to produce TPS in the primary branches of the mother plant.

Sexual seeds of potato (Solanum tuberosum L.) usually emerge poorly under high-temperature conditions (> 25 C). A seedling vigor study was conducted during the warm season (1988-89) in Lima, Peru, and the results of two representative tests. are reported. Two presowing treatments and a rinsed control were compared for seedlingstand establishment in a screenhouse with old (>18 months) and new (> 6 months) sexual seeds of three potato crosses. The treatments consisted of soaking the seed in solutions of KN03 + K3P04 at – 1.0 MPa (priming) and gibberellic acid at 1500 ppm (GA1500). Seedling vigor was lower at 34C (February test) than at 29C (November test). In both tests, overall seedling performance was highest in seed of the cross Atlantic × LT-7. Old seed was more vigorous than new seed, particularly when the crosses Atzimba × R128.6 (B2) and Serrana × LT-7 (Cl) were tested at 34C. Priming increased percentage of early (10 days) emergence over the other treatments at 34C and increased seedling dry weight in both tests. GA1500 increased percentage of final (17 days) emergence in crosses B2 and Cl, as compared to rinsing, except at 29C, where there were no significant differences in old seed. For sowing true potato seed at high temperature, a) the genotype is a crucial factor, b) sufficient seed storage (> 18 months) may be essential, and c) seed priming is more effective than the standard GA1500 treatment.

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