Grafting survival rates of different black walnut rootstock-scion combinations and evaluation of seedling growth status

【Objective】Xinjiang is one of the earliest regions in China to plant walnuts (Juglans regia L.), and in 2023, the area of walnuts in Xinjiang have reached 42×104 hm2 , with an output of 133.41× 104 tons, bring economic benefit for farmers in Xinjiang.. The soil in the region has high salinity, and the walnut industry in Xinjiang is currently limited due to lack of good rootstock. Black walnut (J. nigra L.) is a potential excellent rootstock for walnut. In practice, the grafting affinity vary with different combination of scion and rootstock. Therefore, this study aimed to systematically evaluate the graft compatibility of different scion-rootstock combinations of walnut and black walnut to identify the optimal combinations.【Methods】In this study, we constructed Eighteen scion-rootstock combinations with three walnut varieties Xinzaofeng, Wen 185 and Xinxin 2 and six black walnut strains with high resisitanc to salinity. The nursery trees of the rootstocks were planted in 2024 and the scion varieties werer grafted on them by budding. Each combination had 30 plants. Afterwards, 14 indexes such as new shoot length, leaf area and SOD activity were comprehensively evaluated by principal component analysis. 【Results】Xinzaofeng and Wen 185 had the highest survival rate (68.89%, 77.78%) on No. 1 rootstock and better growth potential with the rootstock No. 5/6. Xinzaofeng had higher soluble protein and sugar content with the rootstock No. 6 (P＜0.05) and the lowest PPO activity (12 665.57 U·g-1 ), and the weakest POD and CAT activities with the rootstock No. 4. Wen 185 had highest soluble sugar content and PPO activity with the rootstock No. 5, but the lowest soluble protein content and SOD and POD activities. Wen 185 and Xinxin 2 had the lowest PPO and CAT activities with the rootstock No. 3. Xinxin 2 had the highest survival rate (54.44%) and growth potential and POD activity with the rootstock No. 6, the highest SOD activity (2 123.17 U·g-1 ) with the rootstock No. 5, and the highest soluble sugar and protein content with the rootstock No. 2, but the lowest SOD and POD activities with the rootstock No. 4. The principal component analysis showed that the Xinzaofeng had the highest affinity score (0.659) with the rootstock No. 6. Xinzaofeng had the lowest score (-0.848) with the rootstock No. 4; Wen 185 had the highest affinity score (0.744) with the rootstock No. 5, the lowest score with the rootstock No. 3 (-0.604). Xinxin 2 had the highest affinity score (0.900) with the rootstock No. 6 and the lowest score with the rootstock No. 1 (-0.640).【Conclusion】Based on multidimensional evaluation, the principal component analysis concluded that Xinzaofeng and Xinxin 2 showed the highest affinity with 6 black walnut rootstock. Wen 185 showed the best performance in 5 combinations. It is worth noting that the rootstock No. 4 should not be used as rootstock for Xinzaofeng. The rootstock No. 3 should not be used as rootstock for Wen 185. The rootstock No. 1 should not be used as rootstock for Xinxin 2.