Study On Germplasm And Breeding Of Walnuts

Walnut is an important economic nut crop. The walnut production totaled 420,000 tons in 2005, occupied the first place in the wold. But the acreage of excellent walnut culticars in China is very low. Resulting in, Chinese walnut occupied the lower place in the wold maket. In order to improve the competabiliy of Chinese walnut industry and retain the sustainable and healthy development, it is very important to make studies on germplasm and breeding of walnut. In this study on germplasm and breeding of walnut, the main results are listed in the following.1. Fifty eight data were used to describe the botany and biology characteristics of walnut. And a excele-database including 50 walnut germplasm was builted. According to the practicability and diversity, 4 excellent walnut germplasm, including"Bokexiang","Xiangling","Liaoning No.5"and"Beijing 746", were selected.2. Nine SSR primer pairs originally designed in black walnut (Juglans nigra L.) were used to amplify SSR fragments for 35 samples of Sect. Juglans, including 29 samples of J. regia, 2 simples of J. sigillata and 4 hybrids of J. sigillata×J. regia. The 9 pairs of SSR prmers generated a total of 47 alleles. The number of alleles per locus ranged from 3 to 9, and averaged 5.2. The value of allelic polymorphism information content (PIC) ranged from 0.3188 to 0.7902, and averaged 0.6357. In 9 SSR loci, the number of heterozygosis locus per sample ranged from 1 to 6, and the heterozygosity per sample ranged from 0.11 to 0.67. The 35 samples of Sect..Juglans could be clustered into 4 groups with UPGMA method. In one group, one Shanxi sample being as Qinba (West china) walnut clustered together with Huabei (North China) walnut. And another two Shanxi samples being as Qinba walnut clustered together with Xinjiang walnut. It indicated that, Qinba walnuts, probably belong to Huabei and Xinjiang ecological type. In the dendrogram, the 2 samples of J. sigillata clustered in the same group with Tibet walnuts, it identified that the J. sigillata and Tibet walnuts have closely relatedness, and the J. sigillata probably be origin in Tibet. But the J. sigillata is one independent species or belong to one ecological type in J. regia, the further studies are needed.3. The fingerprints of 40 Cultivars or lines of J. regia L. were established using 6 SSR markers. Twenty seven Cultivars or lines can be identified using WGA32 and WGA276 SSR markers, 32 Cultivars or lines can be identified using WGA32, WGA118 and WGA276, and it needs 6 SSR markers to identify the 40 Cultivars or lines.4. After storing 2 to 3 weeks under the condition of 4℃, the activity of J. sigillata Pollen ranged from 25% to 40%, indicating that the pollen could keep the need of crossing. Inorder to get new varieties with light kernel, early-bearing characteristic and relatively strong anti-coldness, the hybridization of J. regia×J. sigillata were conducted, after 6 years'work, 7872 hybrids were obtained, and 12 excelent individuals were selected according to the nut characteristic. The kernel colour of the excelent individuals was improved clearly.Inorder to get new varieties with perfict nut quality, high yield, early-bearing characteristic and strong antistressness, seedlings selection was conducted, and 16 excelent individuals were choosed from 2820 seedlings.5. The 5 hybrids of'Xiangling'×'Santai'and 4 hybrids of'Xiangling'×'Yunxin 26'were identified using 9 SSR markers. The results showed that the 5 offspring of'Xiangling'×'Santai'except'Santai-4'were their hybrids,'26-1','26-2'and'26-3'were the hybrids of'Xiangling'×'Yunxin 26'.