Studies On Genetic Diversity Of Macadamia (Macadamia Spp.) Germplasm Resources

Macadamia spp.,a perennial evergreen tree,belonged to the genus Macadamia of the Proteaceace family.The kernel of Macadamia nut was nutritious and delicious;its consumption could modulate favorably the risk factors for coronary artery diseases in hypercholesterolemic subjects,so it came to be favored by more and more people,and to be planted broadly in the tropical and south subtropical regions around the world.At present,23 species have been recognized in the genus macadamia,but only two species were grown for commercial purpose, which were Macadamia integrifolia Maiden et Betche(or "smooth-shell macadamia")and M. tetraphylla L.A.S.Johnson(or "rough-shell macadamia").Up to now,over 80 cultivars of macadamia have been introduced into China from Hawaii, Australia,Thailand,etc.However,domestic researching almost focused on relatively simple observations of morphology and biology of the cultivars,and regional variety trials as well. Information on the genetic backgrounds of macadamia germplasms introduced was very limited, which might lead some questions such as mating of cultivars,selection of cross-breeding parents, sightless introduction of cultivars,etc.and then might have a negative influence on sustainable and healthy development of macadamia industry in China.Therefore,it was of great importance to study the genetic diversity of macadamia germplasms.Nowadays,morphological marker and DNA molecular marker technologies were extensively applied to the analysis of genetic diversity of crops.In this paper,both of them were used to analyze 64 accessions(one third of which are never analyzed in the past)introduced by Yunnan institute of tropical crops.41 morphological indexes were selected according to the criterions of UPOV and Chen Yeyuan and methods of Simpson & Allan and Du liqing as well as performance of macadamia's growth in the local.ISSR molecular marker technology was also applied due to its advantage of high efficiency,simpleness and better repetition.The following were the main results: 1.Statistic analysis and R-style cluster analysis were used to examine the 41 morphological characteristics(including 19 quantitative traits and 22 qualitative traits)of macadamia based on the software DPSv7.05.The result showed that:at the Euclidean distance approximate 11.72,41 characteristics were divided into two groups.There was significant effect on among characteristics within their group.Almost characteristics were independent and had significant meaning in macadamia's taxology,and it was reasonable of choicing these morphological characteristics to analyse these macadamia germplasm genetic diversity.2.41 characteristics were used to analyze 64 germplasms based on Q-style cluster.The result showed that:Euclidean distance of 64 germplams rang from 3.15 to 12.39.And the 64 germplams were divided into two groups at the Euclidean distance approximate 12.Group one included only T₂,which belonged to related species of macadamia cultivation.Group two included the others, which could be further divided into three sub-groups at the Euclidean distance approximate 10.The first sub-group included seven accessions:695,900,D4,HY,Guang9 and No.1,2 of M.tetraphylla, which belonged to hybrids of M.integrifolia and M.tetraphylla.The second sub-group included two accessions:A4 and A16,which was similar to M.integrifolia.The third sub-group included the other 54 accessions that were all offsprings of M.integrifolia.The cluster result,based on morphological marker method,was consistent with the existing system of taxology Meanwhile,the blood relationship figure of 64 accessions was also obtained.3.ISSR was used to analyze 64 accessions based on NTSYS 2.10e software.The result showed that 64 accessions were divided into 5 groups at the genetic distance 0.385.The first group included seven cultivars,which all originated from Hawaii's M.integrifolia.The second group included 50 cultivars,the cluster result was not obvious orderly.The third group included only No.1 of M.ternifolia.The fourth group included A4 and A16,the cluster result was same as the breeding data.The fifth group included four cultivars:842,819,D4 and T₂,the cluster result was not obvious orderlyIn a word,the cluster result,based on ISSR marker method,was not obvious orderly.Only partial germplasms' type and blood relationships were consistent with the existing system of taxology.4.The results had relatively obvious difference from two methods.The result based on the analysis of morphological marker was more orderly than ISSR marker.In this paper,the morphological marker system,which was supplied and perfected,was powerful to differentiate the type of macadamia germplasms,and was also relatively effective to identified the blood relationship of macadamia germplasms.5.Genetic distances obtained from the two methods(morphological mark and ISSR marker) indicated that these macadamia germplasms included relatively higher genetic diversity.6.Based on the analysis of morphological and ISSR methods,the results revealed that,among the 64 accessions,the relationship between HAES788 variation and HAES788 were relatively far, so HAES788 variation could be evaluated and utilized as a new cultivar;No.1,2 of M.tetraphylla probably also belonged to the offsprings of M.integrifolia and M.tetraphylla.