Physiological Mechanism Of Drought Resistance For Different Genotypes Banana

Banana (Musa paradisiacal L.) belongs to Musa of Musaceae. Banana is one of the most important economic crops in the south of China, including Hainan, Guangdong and Guangxi. Because of large leaf area, shallow root system and rapid growth rate, banana growth and development need high water. Banana drought injury was severely threatened its production and development, especially in the cultivated area of China due to seasonal water shortages as well as in the world. However, physiological mechanism of drought resistance for banana had not been done systematically. Physiological mechanism of drought resistance for different genotypes banana were studied using the way of identification of interior and identification of field. The purpose of the experiment was to provide a theoretical basis for the drought resistant breeding and cultivation of banana.(1) Three different genotypes of banana plantlets those were Brazil banana (M. AAA cavendish var. Brazil),Diwangjiao (M. AA Pisang Mas cv. Mas) and Fenjiao (M. ABB Pisang awak), were threatened under PEG stress and those concentrations were 0% PEG-6000 (control),5% PEG-6000 (light stress),10% PEG-6000 (moderate stress) and 20% PEG-6000 (severe stress). The changes in three varieties of banana plantlets of root/top ratio,leaves' and roots' related drought resistance physiological characters under different drought stress conditions were determinated. And these characters were analysed by principal component analysis and subject function analysis. The results showed that:1. R/T ratio of Brazil banana, Diwangjiao and Fenjiao plantlets showed an increasing trend with varying drought stress degrees, and the difference between root/top ratio of three varieties of banana plantlets and the control were significant under severe stress. Three varieties of banana decreased area of leaf. Apart from the difference between Diwangjiao and the control under severe stress was significant, the others did not reach the significant level. As drought stress increasing, root vigor in three varieties of banana were significant decreased.2. L value, a value and b value of Brazil banana, Diwangjiao and Fenjiao had declined with drought stress increasing. The content of chlorophyll of Brazil banana and Diwangjiao plantlets were decreased significantly under light stress and moderate stress; while severe stress in the content of chlorophyll were higher than the control, and Brazil banana was significant different with the control, while Diwangjiao was not significant different with the control. The content of chlorophyll of Fenjiao plantlets were reduced significantly by 8.5%, 13.3% and 4.9%.3. As drought stress increasing, plasmamembrane permeability and MDA content of leaves, MDA content of roots in three varieties of banana were increased significantly.4. Proline, soluble protein, soluble sugar content of leaves in the three varieties of banana were increased significantly under drought stress. As drought stress increasing, soluble protein, soluble sugar content of roots in the three varieties of banana did not showed a sustained upward trend.5. SOD, POD activity of leaves in three varieties of banana under three stress levels showed a significant increase trend under the overall, and as stress levels increasing, amplitude of variation of their activities increased gradually. Under severe stress, SOD activity of three banana were increased by 28.8%,36.2% and 41.3% compared with the control, while the POD activity were increased by 21.9%,38.0% and 57.7%. SOD, POD activity of roots in three varieties of banana under three stress levels showed the same trend to leaves under the overall.6. With the increase of stress levels in Brazil banana,Diwangjiao and Fenjiao plantlets, Pn,Tr,Gs showed a significantly downward trend, while the decline of Pn of Brazil banana was large, decreased by 80.1%,83.4% and 92.4%. While intercellular Ci concentrations of the three banana varieties were significant higher than the control.7.23 characters were analysed by applicating principal component analysis. Leaf transpiration rate, leaf proline, leaf chlorophyll, leaf relative conductivity, leaf soluble protein, root soluble protein, root SOD activity, leaf POD activity, leaf MDA content, root MDA content, leaf soluble sugar had a large eigenvectors, summed up the majority information of the 23 characters and were the important indicators to evaluate the drought resistance of banana.8. By applicating the fuzzy subjectional function, Brazil banana, Diwangjiao and Fenjiao were comprehensively evaluated. The drought resistance of three varieties of banana was Fenjiao(ABB)>Diwangjiao(AA)>Brazil banana(AAA). It was showed that the different genotypes and drought resistance of banana was a sort of relevance. It was found in these three varieties of banana that the more B genome was, the more stronger drought resistance of banana was; the more A genome was, the worse drought resistance of banana was.(2) In banana germplasm nursery, Tropical Crops Genetic Resources Institute, Chinese Academy of Tropical Agricultural Sciences, we selected 9 different genotypes and 28 banana varieties. Their drought resistance related morphological and anatomical structure characters of leaves were observed by paraffin sectioning and the plasmamembrane permeability, MDA content and leaves chromatic value of leaves were measured. Cluster and discrimination analysis techniques were used to study drought resistance related characters of 28 different varieties of banana. The results showed that: 1. Among the tested varieties, differences of thickness of leaf, thickness of upper leaf epidermis and cutin, thickness of palisade tissue, thickness of spongy tissue, thickness of lower leaf epidermis and cutin, CTR, SR, plasmamembrane permeability, MDA content and leaves chromatic value were extreme significant.2. The correlation coefficients of CTR and plasmamembrane permeability, CTR and MDA were -0.5986 and -0.5735, checked for an extreme significant negative correlation by F test, and the correlation coefficient of plasmamembrane permeability and MDA was 0.8743, checked for an extreme significant positive correlation.3. By cluster analysis used to CTR,28 banana varieties could be divided into three groups. By cluster analysis used to plasmamembrane permeability,28 banana varieties could be divided into two groups. By cluster analysis used to MDA,28 banana varieties could be divided into three groups. Cluster and discrimination analysis techniques were used to study CTR, plasmamembrane permeability and MDA of 28 banana varieties. They were classified into three groups according to these characters, then three discrimination models with better distinguishing abilities were established. Also it was found that the genome types of banana did not determine its drought resistance. There is a tendency that varieties with more and more B genome were drought resistance stronger, and with more and more A genome were drought resistance worse; drought resistance in tetraploid were stronger than diploid and triploid. The reason will study applying genetics and molecular biology further.