Study On Tomato Taxonomy, Cold Tolerance And Cross Breeding Through Pollen Features

1. In this experiment, pollen grains of 10 different cultivated, semi-cultivated, and wild tomato varieties were examined by scanning electron microscope (SEM). Result shows, tomato pollens of different varieties have a same spherical shape; The pollens have different sizes, but the size can't serve as a exact basis for tomato taxonomy; From the comparison of pollen exine sculpture, tomato pollen grains can be divided into 3 types: 1. Coarsely wartyranulate; 2. Smoothly wartyranulate; 3. Reticulateranulate. The result of this taxonomy method is similar to that of taxonomy based on biological features, Meanwhile, the character of tomato hybrid and embodiment of evolution on pollen exine sculpture are also discussed.2. 6 tomato varieties were treated by low-temperature stress and identified by different degrees of cold tolerance . Their pollens were treated under different temperature. Results shows: Pollens started to germinate 6 and 2~3 hours later respectively under 8 and 12 , the germination rates of chill-tolerablevarieties were much higher than that of chill-intolerable ones and this is in significant positive correlation with their chill tolerance nature (coefficient correlation were 0.9054 and 0.9238 respectively).Pollens treated by 16 and 24 germinated much earlier and had a even higher germination rate than that treated by 8 and 12 ,but there were no significant differences among varieties, so their correlation with chill tolerance did not reach a significant level; The pollen tube growing speeds of chill-tolerance varieties were higher than that of chill-intolerable ones under low temperature (8 and 12 ), but under 16 and 24 , pollen tube of all varieties grew fast, no obvious differences among those varieties.3. The tomato pollen viability under different growing and storage conditions were measured. Pollen viability of tomato growing in the field is higher than that in the greenhouse( temperature were 25 and 36 respectively when measured). Pollen viability of flower opened the first day is also higher than before or after that. Pollens from the first day of flowering stored under 24 and RH78%~80% for 3 days, theviability drops to 22. 7%, while those stored under 4 and RH21%for one week, still have a viability of 42%. Pollens stored underlow temperature and high humidity or room temperature(24 ) andlow humidity get a lower germination rate than those under bothlow temperature and low humidity.