Abstract
Poor fruit set during winter period is one of the biggest problem in plastic tunnel watermelon cultivation. Hand pollination is inevitable to maximize fruit set of the winter watermelon. Productivity and viability of pollen grain and organic solvents for pollen storage were investigated. All cultivars produced more than 10 mg/flower except for 'Kumchun' cultivar. Pollen amount per flower were 13.8 mg in 'Bok' and 12.1 mg in 'Speedkul'. Germination rate of pollen grains incubated at $30^{\circ}C$ right after soaking in pentane solvent were 76% in 'Kumchun' as the lowest and 92% in 'Apollokul' as the highest. The pollen of 'Bok' showed the highest germination rate by 75% after a 15-day storage in pentane. All cultivars showed their pollen germination rate below 25% after a 24-day storage. Among the cuitivars, speed of pollen tube growth in vitro were relatively lower in 'Kumchun' and 'Sambokkul' by below $50\;{\mu}m/hr$. Pollen tube of these cultivars tended to burst during its elongation on the medium. Pollen stored 24 hrs in organic solvents showed 45, 39, 34, 23, and 19% of germination in pentane, ethyl ether, n-hexane, ethyl acetate, and acetone, respectively. Compared with light condition, pollen viability was higher in darkness during pollen storage in organic solvents. Pollen grain was susceptible to the organic solvent. The viability of pollen grains seems to be influenced greatly by duration of soaking pollen in organic solvent and the polarity of solvents. Organic solvent damages surface of pollen grain and extent of damage was varied by the solvents.
화분량은 '금천' 수박을 제외하고 응화 1개당 10mg 이상이었다. '복' 수박은 1화당 화분무게가 13.8mg이었고, '스피드꿀' 수박은, 12.1mg으로 겨울철 저온기 재배에 인공수정용 화분생산 품종으로 적당한 것으로 판단된다. 유기용매 침지 후 즉시 건조된 화분발아율은 '금천' 수박이 67%로 기장 낮았고 '아폴로꿀' 수박이 92%로 가장 높았다. 유기용매에 15일간 저장했을 경우 '복' 수박 화분의 발아력이 74%로 가장 높았다. 저장 24일 후에는 5품종 모두 25% 이하의 발아율을 나타내었다. '금천'과 '삼복꿀' 수박의 화분관 신장속도는 $50{\mu}m/hr$ 미만(저장 24일)으로 다른 품종보다 낮았으며, 벌이도중 화분관이 파열되는 경우도 발생되었다. 유기용매 저장 24시간 후 화분발아율은 pentane, ethyl ether, n-hexane, ethyl acetate, acetone에서 각각 45, 39, 34, 23, 19% 순이었고 유기용매 침지시간이 길어질수록 화분활력이 급격히 감소되었다. 화분 표피는 유기용매에 저장한 시간이 길어질수록 장해를 많이 받았는데 유기용매의 종류에 따라 장해정도가 달랐다. '복' 수박이 화분량, 화분활력, 저장성이 우수하였는데 저온기 착과율 증진을 위한 화분생산 품종으로 보여진다.