Development Of Autotetraploid Plants Derived From Banana Diploids And Exploring The Mechanisms Of The Genetic Variability

Bananas(Musa spp.)are large herbs that are native to Southeast Asia and the Pacific.There are nearly one thousand varieties of cultivated bananas in the world,but there are only more than ten major cultivated species,including AAA,AAA and AAB.Because the cultivated banana is triploid and has low fertility,it is difficult to carry out large-scale germplasm creation through cross breeding.Cell engineering mutagenesis technology can induce genetic variation through physical radiation and chemical mutagenesis,which is widely used in banana breeding and germplasm creation.However,the efficiency and success rate of cell engineering mutagenesis are closely related to the variety,explant type,medium formulation and other factors.In this paper,we planned to induce polyploid by different media and obtain tetraploid by chromosome doubling,and carried out the germplasm creation of banana polyploid,and studied the phenotypic changes and internal mechanism of tetraploid plants after successful doubling.The main results are as follows:1.MBC induction medium and P4 culture medium were used to induce polybuds of10 banana cultivars(including AA,AB,BB and AAA genomic types),respectively.Among the seven AA genotypes,only ’Wiliman’ did not induce polybuds in MBC medium.No polybuds were induced in BB genotype ’Tani’;In AB genotype’Kunnan’,polybuds were induced in both media with similar induction effects,while in AAA genotype ’Khai Thong Ruang-Ibota’,only polybuds were induced in MBC medium.The acquisition of polybud materials can provide acceptor materials for the subsequent physical radiation or chemical mutagenesis to produce more stable mutations.2.The differentiated buds of 12 banana varieties were induced by colchicine doubling,and ploidy identification and screening of the mutated differentiated buds were performed by flow cytometry,and the differentiated buds that were not successfully doubled or chimeric were eliminated.The differentiated buds identified as tetraploid were further propagated.The tetraploid buds of the first generation of 6 AA genotypes were obtained.Two cultivars(’ Mjenga Gros Michel Diploide ’(MGMD)and’ Xing Haigong ’)were identified as tetraploid buds for three successive generations,and regenerated seedlings were also obtained.The regenerated plants were identified as tetraploid plants by root tip chromosome count.3.We evaluated the two varieties’ MGMD ’and’ Xing Haigong ’with successful chromosome doubling.It was found that the tetraploid plants showed certain "giant" after doubling.For example,the plant height,stem base thickness,longest root length,leaf thickness,leaf area and chlorophyll content of ’MGMD’ were increased by 62.6%,75.1%,12.9%,39.7%,15.8% and 22.2%,respectively.After doubling,the plant height,stem base thickness,longest root length,leaf thickness,leaf area and chlorophyll content of ’new haigong’ were increased by 27.2%,60.2%,29.3%,44.2%,25.3% and16%,respectively.4.The transcriptome analysis of ’MGMD’ and ’Xing Haigong’ seedling leaves showed that the differential gene expression was mainly annotated to the plant hormone signal transduction pathway,plant-pathogen interaction,plant MAPK signal pathway,amino acid sugar and nucleotide sugar metabolism,starch and sucrose metabolism.5.Based on the double success ’MGMD "and" xin hai gong’ seedling leaves of metabonomics analysis,results show that the tetraploid plants most primary metabolites is significantly higher than that of diploid,in amino acid metabolism,carbohydrate metabolism,and other secondary metabolites biosynthesis,multiple metabolic pathways of cofactors and vitamins significant enrichment,These results suggested that genome doubling might promote the accumulation of metabolites in banana seedling primary growth.6.By doubling plant transcription and metabolic group of conjoint analysis,to determine the change in both banana varieties of metabolic pathways are: flavonoids biosynthesis pathway,carotenoid biosynthesis pathway,porphyrin and chlorophyll metabolic pathways,plant hormone signal transduction pathway,tryptophan metabolism pathway,belladonna,piperidine and pyridine alkaloids biosynthesis pathway.