Breeding report of a new early ripening mini-type watermelon variety ‘Zhongtianhong'

Abstract: ‘Zhongtianhong'is a new early ripening mini-watermelon variety. It is selected by crossing inbred line No. 26 as female parent with inbred line No. 93 as male parent. No. 26 was isolated from the progeny of Japanese‘Zaochunhongyu'and inbred for eight generations. No. 93 was derived from the cobalt-60 irradiated‘ZG-6'and inbred for sixteen generations. The fruit is highly round in shape, marked on green surface with dark green toothed stripes. The fruit index is 1.05. A little powder is covered on the fruit surface. The rind is 0.4 cm in thickness. The flesh is red and crispy with soluble solid content of 12%in the fruit center and 10% near the rind. The average fruit weight is 1.6 kg and the largest 2.9 kg. The color of seed coat is brown. Averagely there are about 140 seeds in each fruit and the 1 000-seed-weight is about 38 g. In the protected field of Zhengzhou(113.65 degrees east longitude and 34.76 degrees north latitude), it is cultivated from February to June in the spring. The plant growth period is about 100 days, and the fruit growth period is 32 days. In the summer, the plant growth period and fruit growth period are 75 days and 25 days, respectively. The first female flower appears on the 6th to the 10 th node, and the interval between the two neighboring female flowers ranges from 5 to 7 nodes. In order to ensure the fruit quality, the second or the third female flower is selected for fruit-setting normally. This variety shows good resistance to external stresses, such as low temperature and poor light. Importantly, it is somewhat resistant to Fusarium wilt. The fruit has a shelf life of two weeks at room temperature. This variety has wide adaptability and can be cultivated in the main domestic watermelon growing region under protection or in open field. Compared with the field cultivation, protected cultivation can bring more economic benefit. Theyield can reach up 2 715 kg per 667 m² on average. This variety can be cultivated by means of verticalculture or creeping-culture. For vertical-culture, one or two vines can be remained. The optimum planting density for single vine is 2 200 plants per 667 m², while the density for double vines is 1 800 plants.For creeping-culture, the optimum planting density is 800 plants per 667 m², and two to three vines can be remained. As the mini-watermelon is small in size, the management of irrigation and fertilization is important. The water should be provided at low frequency but in sufficient amount every time from seedling stage to stretch tendril period in order to build strong root system. During flowering period, the water must be controlled strictly. Exceeded water and fertilizer is avoided during the fruit swelling period, and irrigation should be stopped one week prior to harvest. The fertilization is mainly used in base fertilizers including manure and N, P, K compound fertilizers. Additional fertilizer can be supplied with water once during the fruit swelling period.