In Vitro Production And Identification Of Polyploid Banana (Musa Spp.) Germplasm

Banana (Musa spp.) is one of most important staple food crops in tropical and subtropical regions of the world. However, the production of banana is limited primarily by the spread of viral and fungal diseases, such as black sigatoka, fusarial wilt and the bunchy top virus, as well as insect and nematode pest problems. Polyploid breeding is an important approach for improving the output, quality and resistance of banana. In the study, GongJiao, Brazil Xiangjiao and'kangkuyihao' were the trial materials. The rapid micropropagation system in-vitro of banana was studied. Additionally, the methods of inducing banana polyploid were tested by colchicine for obtaining polyploid germplasm, which can provide excellent material and relevant technical information for the inovation of new varieties germplasm and genetic improvement. The major results are as follows:1. Suspension culture for embryogenic cell derived from 6-12th row young floral hands of immature male flower of Gongjiao(Musa acuminata cv. Mas AA)was established. Yellowish and friable embryogenic cultures were obtained after culture for 3 months on callus induction media. The results showed that the MI media (MS basic medium+1 mg/L BIO+1 mg/L IAA+1 mg/L NAA+4 mg/. L 2,4-D+30 g/ L sucrose +7 g/L agar) was the most effective on the callus induction, it caused 47.6 % of the male floral hands to form callus and 7.1%of the induced calli became embryogenic callus. After selection of the cultures for 3 months, homogeneous and yellowish embryogenic cell suspensions(ECS), composed of single cells and small cell aggregates, were established. The growth condition of transplants and root systems is good, with high survival rate. Multiple buds could be induced from meristem of single adventitious bud of these three cultivars in P4 medium consisted of MS basic medium and 6- BA 100μmol/L and IAA 1μmol/L after subculture for five cycles.2. Embryogenic callus of GongJiao(Musa acuminata cv. Mas AA)was treated with 0,0.05%,0.1%,0.2% colchicine for 48h. Embryogenic cell suspensions(ECS) of GongJiao(Musa acuminata cv. Mas AA)was treated with 0,0.01%,0.02%,0.05% colchicine for 24h. Mutiple-buds of Gongjiao(Musa acuminata cv. Mas AA), Brazil Xiangjiao(Musa AAA Cavendish CV.Baxi) and 'kangkuyihao' (Musa AAA Silk CV. 'kangkuyihao')were treated with 0,0.1%,0.2%,0.3%,0.4%,0.5% colchicine for 24,48h respective. Results showed that all three types of the colchicines-treated explant materials including embryogenic cell suspensions, callus and multiple buds, are relatively sensitive to higher concentration of colchicines solutions, in which those of 0.4% colchicines with a treatment duration of 48 h has a marked induction effect on multiple buds, presenting a mortality rate was 47.22% but 18.64% of the progenies were confirmed polyploid by microscopic observation of chromosome number and leaf stomata characteristics.3. The ploidy of plantlets in vitro were identified and the numbers of chromosome is GongJiao 2n= 22, Brazil Xiangjiao and Kangkuyihao are 3n= 33. The mutant plants were identified in system. Homozygous polyploid (Tetraploid Gongjiao 2n= 4x= 44, hexaploid of Brazil Xiangjiao and Kangkuyihao were 2n= 6x= 66) and a few chimeras and few plant with no change in chromosome were obtained by colchicine inducing. Polyploid banana had a good multiplication and rooting effect, which cultivated on the best mediums for normal ploidy plant. Homozygous polyploid of banana were transplanted and survived transitorily. The plant obtained by colchicine inducing reduced leaf stomata frequency but enlarged the size of stomata, and pore inclusions color deepened.