External fruit skin colour inheritance and pollen storage to be used in breeding programmes in summer squash (Cucurbita pepo L.)

ABSTRACT EXTERNAL FRUIT SKIN COLOUR INHERITANCE AND POLLEN STORAGE TO BE USED IN BREEDING PROGRAMMES IN SUMMER SQUASH (Cucurbitapepo L.) Ahmet Sırn ŞENSOY Adviser: Prof. Dr. Nurgül ERCAN M.Sc.Thesis in Horticultural Science September 2004, 62 Pages The objective of this study is to clarify the inheritance of fruit colour and to determine the possible pollen storage conditions in summer squash. Summer squash lines were classified from light green to dark green for the criteria of fruit skin colour at mature stage of development. Inbred lines with light green fruited were crossed reciprocally with the dark green fruited lines. In each cross combination, the Fi plants were selfed to obtain F2 and also backcrossed with the each parent to produce BCi. All F2 and BCi generations were grown in the field and subjected to open pollination. Fruits at mature stage were harvested and their colours were scored in each individual plant. The Khi-square test was used to analyze the data. In this research, it was possible to say that genotype of the line 27 was 1-1/1-1 1-2/1-2, line 39 was L-l^/L-l81 L-2/L-2. And there was a possitive correlation (78%) between the stem colour and the fruit skin colour. It is a necessity to store the pollen, of male flower for later pollination of the female flowers in summer squash due to its monoic flower biology. In this part of the study, the effect of six storage conditions as the combination of two storage temperatures (+4°C and -20°C) and three chemical applications (acetone, benzen, ethyl acetate) on pollen storage were analysed. IVPollen viability was assessed by TTC (75.0%), I/KI (85.0%), Safranin (90.5%) methods and in vitro germination tests (28.0 %). However, the disadvantage of the in vitro germination test was the pollen burst with (58.97%) which varied according to sucrose concentrations. When the pollen collection time was considered, pollens taken from the plants early in the morning resulted with higher germination rates than those of taken from in the afternoon. In this research +4°C was found as the optimum pollen storage temperature (54.47%). Germination rates was 0% at the end 24 hours for the pollens stored at -20°C and room temperature. Germination of pollens preserved in asetone, benzen and ethyl acetate was approximately zero. It is obivious to say that pollen storage in such kind of chemicals is not advisable for squash pollen. KEY WORDS: Cucurbita pepo, squash, pollen storage, colour inheritance COMMITTEE: Prof. Dr. Nurgûl ERCAN Prof. Dr. Hüseyin PADEM Assoc. Prof. Dr. A. Naci ONUS