Development and maintenance of gynoecious lines of cucumber (Cucumis sativus L.)

The study aimed to develop gynoecious lines of cucumber (Cucumis sativus L.) by isolating, selfing and evaluating of selfed progenies from original populations and to maintain these lines by using chemicals to induce staminate flower for genetically selfing. Two F 1 cucumber cultivars of long type (Seminis-1 and Seminis-2) and three short type (Siminis-3, Micro-c and Bingo) from Thailand and three OP cultivars of long type (Long Green, Kusle and Bhakatpur Local) from Nepal were evaluated for gynoecious sex expression. Among the F 1 populations, only Bingo expressed gynoecious type for 5% and the rest were predominantly gynoecious sex type. Open-pollinated populations only expressed monoecious sex type. During the process of gynoecious line development through inbreeding and plant-to-row selection it took three consecutive selfing generation (S 3) for complete gynoecious development of SE1-G (long) and SE3G (short) lines which were isolated from the original population of Seminis-1 and Seminis-3 respectively. Among the used chemical, silver nitrate (AgNo3) was found statistically significantly superior over gibberellic acid (GA3) and silver thiosulfate (Ag(S2O2)2) for effective staminate flower induction for the maintenance of gynoecious lines. The highest sex ratio (M/F) 0.80:1 in SE1-G line and 0.89:1 in SE3-G line was observed by first lateral chemical application from the chemical silver nitrate 400 and 300 ppm applied twice respectively which confirm the highest possibility of flower synchronization.