Karyotype Analysis Of Banana (Musa Spp.) Germplasm And Identification And Selection Of Genetic Variants

Banana (Musa spp.) is one of the most important tropical and subtropical fruits, which is also related to the world food security, regional development and human health. However, the banana is facing serious threat of pests and diseases, and how to cultivate high-quality and high-yield cultivar of banana, which becomes an urgent problem for banana industry. For most Banana cultivars are high sterility, it is difficult to use traditional breeding methods for genetic improvement. But, biotechnology methods, such as genetic engineering, protoplast fusion and mutation breeding, are expected to achieve the purpose of improving banana germplasm. The identification and screening of the banana embryogenic cell suspension (ECS) variant regenerated plants is an new approach for banana germplasm innovation and breeding, combined with the polyploidy breeding methods, which is expected to breed new superior banana cultivars with good agronomic value as well as disease and pest resistance.In this paper, karyotype analysis was performed to investigate the chromosome features of 6 banana (Musa spp.) cultivars in relation to A genomes by using the method of wall degradation hypotonic. Results showed that the analysed cultivars of diploid or triploid that contained only A genomes, viz. AA or AAA, varied in karyotype characteristics. The karyotype formula and its type were 2n=3x=33=3M+27m(3SAT)+3sm and "1A" for 'Tianbaojiao'(AAA),2n=2x=22= 2M+18m(2SAT)+2sm and "2A" for 'Hainangongjiao'(AA), respectively. The karyotype formula for 'Rose'(AA),'Pisang Mas'(AA),'Kangku 1'(AAA) and 'Kangku 5'(AAA) were 2n=2x= 22=2M+16m(SAT)+2sm+2st,2n=2x=22=4M+16m(SAT)+2sm,2n=3x=33=6M+15m (3SAT)+12sm,2n=3x=33=6M+15m (6SAT)+12sm (3SAT), respectively, whereas all these four cultivars exhibited a karyotype asymmetry of type "2B"The long-term subculture banana ECS cytological studies have shown that the number of cells of which chromosome number are variety in ECS increased and the overall differentiation of somatic embryos gradually decreased, as the number of subculture increasing. Musa itinerans Cheesman, Kangku land Musa paradidiaca L. ECS in the course of subculture, the number of chromosomes in embryogenic suspension cells are unstable, whcih ranging from a few to more than one hundred and the ECS are mixoploidy. Musa itinerans Cheesman, Kangku land plantains subculture 1.5a, the suspension cell mutation rates were 96.3%,93.0% and 94.0%, respectivelyThrough screening the regeneration banana of ECS mutants, we have obtained dwarf type, distortion type, embedded leaf, narrow leaf type and wave type and other types of plants, and eight homozygous 1 hexaploid plants via banana ECS polyploid induction, morphological and cytological identification as well.We observed and compared the Kangku 1 triploid and hexaploid in plants form, leaf, stomata, guard cells and guard cell chloroplast number and so on. The results showed that:the leaf length, width and thickness of 1 hexaploid resistant plants withered are higher than the triploid plants:six times the body of chloroplast number in guard cells were increase significantly but the stomatal density of stomata decreased. Leaf thickness, stomatal density and guard cell chloroplast number were of significant difference by analysis of variance.