Date of Award
Program or Major
Doctor of Philosophy
Lincoln C Peirce
The feasibility of applying low temperature as a screen for selecting early gametes during pollination of tomato flowers was investigated. Pollen germination and tube growth on solidified agar were evaluated at 8, 15, or 25 C after 6, 12, 18, or 24 hours of incubation for two early-, two intermediate-, and two late-maturing tomato cultivars. Pollen from early cultivars showed superior germination and tube growth at 25 C, whereas pollen germination and tube growth of late cultivars were greatest at 15 C. Pollen germination and tube growth of the two early and two late cultivars were evaluated at three (three hour incubation) or five (six hour incubation) temperatures between 10 and 16 C. The relationships between temperature and in vitro pollen germination or tube growth fit a second degree polynomial for all cultivars. The relationship between optimal temperatures for pollen germination and tube growth and the maturity of the cultivar was further investigated by placing pollen from early and late cultivars on intermediate-maturing females and exposing plants to 25 C day/20 C night and 15 C day/10 C night temperatures. Low temperature pollen germination and tube growth rate for all cultivars, regardless of maturity class.
To simulate a population of segregating gametes, pollen mixtures from early and late cultivars were applied to intermediate females under normal and low temperatures. After 48 or 72 hours, styles of pollinated pistils were cut. Low temperatures severely reduced percent fruit set and number of seeds per fruit. However, pollen of early-maturing cultivars had no competitive advantage at either temperature.
Hybrids from crosses of similar and different maturity classes were artificially self-pollinated under low and normal temperatures, and after 72 or 96 hours, styles were cut. Low temperature self-pollinations reduced percent fruit set and number of seeds per fruit. Field comparisons of F$\sb2$ populations derived from low and normal temperature self-pollinations revealed no significant shifts in earliness.
Under low or normal pollination temperatures, in vitro pollen germination and tube growth did not correspond to in vivo germination and tube growth. Furthermore, the gametophytic selection scheme used did not cause significant shifts in maturity.
Crispi, Mark Lawrence, "Gametophytic selection for early maturity in tomato (Lycopersicon esculentum Mill)" (1991). Doctoral Dissertations. 1640.