SCREENING POTATO (SOLANUM) SPECIES FOR MALE-FERTILITY UNDER HEAT-STRESS

Heat stress limits botanical seed production by inhibiting flowering, pollen production and pollen viability. Three accessions (PIs) of each of 23 diverse Solanum species were screened for stability of fertilit y parameters under heat stress. Seedlings were grown to flowering in t emperate conditions (16-25 C), then treated with three weeks of heat s tress of up to 45 C for 4-6 hours per day at midday with nighttime low s of 18 C, and compared to temperate-grown controls. A highly signific ant effect of species, temperature, and their interaction was detected for flowering. This means species were inherently different and heat had a general depressing effect, but the degree of that effect varied among species. While most species had little flowering in the hot hous e, S. commersonii and microdontum flowered significantly more there th an in the temperature house. Of species which flowered in hot conditio ns, some shed no pollen and some had good shed of mostly dead pollen, but only S. commersonii, jamesii, kurtzianum and megistacrolobum had g ood flowering, pollen shed and viability. This work is expected to con tribute to the study of the genetic and physiological bases of heat st ress fertility, true potato seed (TPS) breeding, and possibly improvem ent of tomato production under heat stress.