Tetraploid Induction Of 'Hongyang' Kiwifruit And Primary Study On Resistance To Bacterial Canker

Kiwifruit is a dioecious liane which belong to Actinidia Lindl. of family Actinidiacea. China is the original center of kiwifruit, where there have abundant wild resource.The nutritive value and medical value are both high in kiwifruit, which is known as 'the king of fruit', it has been gradually became an important constituent of fruit industry development. But with the expansion of the scale of kiwifruit cultivation, disease species and damage degree are also growing, which bring serious threat to kiwifruit production. Among which, bacterial canker is a devastating disease and there is no valid way to eradicate.At present, research about kiwifruit mainly concentrated in cultivation physiology, tissue culture and medicine, but the research about raising its nutrition content and resistance to disease through changing there ploidy was very less. In this experiment, 'Hongyang" kiwifruit was used as the material, firstly, established rapid propagation system. Then explored the optimum conditions to obtain tetraploid by colchicine induction technology, compared for morphological characteristics and resistance to bacterial canker between tetraploid and diploid of'Hongyang'kiwifruit, which made a foundation for further breeding of new varieties with higher nutrition value and excellent resistance to bacterial canker.The main results were as follows:1. Established rapid propagation system with the diploid plants and obtained the best sterilization of explants:the explants were dipped in the scour 10 minutes and washed 20 minutes by tap water, then sterilized 10 seconds by 75% alcohol and 4 minutes by 0.1% HgCl2, rinsed 5 times by sterilized water. The highest differentiation rate of adventitious buds was on the culture medium with WPM+0.6mg/LTDZ+0.1mg/L NAA, under this condition, the radio of adventitious buds differentiation reached 80% and mean of buds was 2.0; the optimal medium for multiplication was MS+2.0mg/L6-BA+0.04mg/LNAA, multiplication coefficient reached 5.5; the best medium for rooting was 1/2MS+0.6mg/LNAA, the rooting rate was 90% and mean of roots was 7.9, the states of plantlets and roots were good.2. Used immersion method and mixed culture method for tetraploid induction by colchicines, the results indicated that:the most effectively induction of immersion method was soaking in colchicine for 48h, the induction rate rached 20%, tetraploid induction rate reached 15%; the most effectively induction of mixed culture method was culture in the medium with 20mg/L colchicine for 10 days, the induction rate reached 10%, tetraploid induction rate was 5%. In contrast, the immersion method is more beneficial to the induced tetraploid of 'Hongyang' kiwifruit. After the observation on chromosome numbers of the induced plantlets, the chromosome number was 2n=4x=116. The multiplied and rooted of tetraploid was good with the optimal medium of diploid, the multiplication coefficient reched 4.2, rooting rate was 70% and mean of roos was 4.0, but the rooted speed was slower than diploid.3. Compared morphology, stomata and guard cell properties of tetraploid and diploid of'Hongyang'kiwifruit. The results indicated that:the tetraploid plants grown robuster than diploid, the stems and leaves were thicker. The leaves thickness, length and width of tetraploid were 118%,148%,106% of diploid respectively, the leaves index was 76.6% of diploid. Chlorophyll comtent of teraploid leaves increased which was 182% of diploid. The length and width of guard cells increased too, which were 145% and 133% of diploid. But the stomatal density declined, which was 52.5% of the diploid.4. Compared drought and heat resistance of tetraploid and diploid. The results indicated that:the leaf water retention of tetraploid was higher than diploid, was 157% of diploid; Cell damage and permeability rate were lower than the diploid, were 36.4% and 65.9% of the diploid. It explained that the drought and heat resisitance of tetraploid are stronger than diploid..5. Activity and isozyme electrophoresis of POD and SOD in tetraploid and diploid were studied. The results indicated that:the POD and SOD activity of tetraploid were all higher than which of diploid; The isozyme bands of the tetraploid was as the same with the diploid, The enzyme activity may explained that the resistance of the tetraploid was stronger than diploid. 6. Isolation, purification and pathogen infection of bacterial canker were studied preliminarily. The results indicated that:two bacterial strains were obtained after isolation and purification, the morphology and pathogenic of the bacterial strain were identified, the bacteria was preliminarily identified as pseudomonas syringae pv actinidia.The leaves of diploid and ten lines of tetraploid were infected in vitro. The result indicated that:the leaves of diploid were susceptible 3 days after infection,8 lines of the tetraploid were susceptible 7 days after infection, the other two were not susceptible.