Breeding report of ultra-dwarf banana cultivar ‘Zhongjiao No.12 ’

Abstract: ‘Zhongjiao No.12 ’(Musa spp. Cavendish‘ZJ12’), a new dwarf banana cultivar, was ob- tained by 60Co-γ radiation mutagenesis on embryogenic cell suspension line (ECS) of‘Baxijiao’(Musaspp. Cavendish‘Baxi’), and the progeny with field screening process.‘Baxijiao’ECS was mutated by 60Co-γ radiation, and mutagenic materials was sub-cultured and used for tissue culture seedlings. Bio- logical characteristics and fruit quality of the resulting plants were investigated in field. Superior plant with comprehensive characters of dwarfing and early-fruiting with stable genetic traits was screened out. From year of 2013 to 2014, a variety comparison test was carried out in Guangzhou, Dongguan, Longmen of Guangdong province, and Taian city of Shandong province. From year of 2013 to 2015, multiple regional tests and production tests were conducted in provinces of Guangdong, Guangxi, and Shandong. The new cultivar was licensed by the Ministry of Agriculture in May 2017. The plant of this species is significantly dwarfed, and the height of the false stem in the field is 0.82-0.95 m, with pressed and shorter leaves and shorter petioles compared with the cultivar of‘Baxijiao’. The fruit panicles are short cylindrical, compact in structure, neat in comb and good in commodity character. Ripe fruit skin is yellow, the flesh is yellow white, with sweet flavor. The fruit edible rate of 68.63%. The soluble solids content of fruit is 19.9%, titratable acid content 0.29%, soluble sugar content 16.2%, sucrose content 8.5%, reducing sugar 13.4%, and vitamin C content 12.10 mg·100 g^-1. The growth cycle was relatively short, and the new plantain was about 285-310 days, 60-70 days shorter than conventional Cavendish cultivars. The average plant yield of new plantain is 8.4 kg, and the yield per 666.7 m2 is 1 680 kg. It is middle-tolerant to Fusarium wilt disease, resistant to wind, and no resistance to cold. The fruit has short storage-life, cold (14-18 °C) storage time is 10-12 days, and shelf life is 5-6 days, after storage the fruit aroma is quite strong. This cultivar is suitable for popularizing and planting in the main banana produc- ing areas of south China, and also could be planted in greenhouse in north China. This variety can bear fruits next year after planted. Orchard should choose neutral sandy-red soil which is flat and has ability of moisture and fertilizer retention; spacing in the rows and spacing between rows are 1.5 m×1.5 m, and 180-200 plants per 666.7 m2. One healthy sucker per plant could be maintained for one more season and renewed every two years with healthy tissue-cultured seedlings. Scientific fertigation is suggested based on banana growth and development stage, and more potassium fertilizer is needed in flowering and fruit bearing stage. With comprehensive control technology, attention should be paid to diseases of Fusarium wilt, leaf spot and heart rot, and banana weevil and nematode in old banana orchard. Fruiting in low temperature period in frost area in winter should be avoided.