Trichoderma asperellum strain 6S-2 with biocontrol effects and potential growth-promoting properties was made into a fungal fertilizer for the prevention of apple replant disease (ARD). 6S-2 fertilizer not only promoted the growth of Malus hupehensis Rehd seedlings in greenhouse and pot experiments, but also increased the branch elongation growth of young apple trees. The soil microbial community structure changed significantly after the application of 6S-2 fertilizer: the relative abundance of Trichoderma increased significantly, the relative abundance of Fusarium (especially the gene copy numbers of four Fusarium species) and Cryptococcus decreased, and the relative abundance of Bacillus and Streptomyces increased. The bacteria/fungi and soil enzyme activities increased significantly after the application of 6S-2 fertilizer. The relative contents of alkenes, ethyl ethers, and citrullines increased in root exudates of M. hupehensis Rehd treated with 6S-2 fertilizer and were positively correlated with the abundance of Trichoderma. The relative contents of aldehydes, nitriles, and naphthalenes decreased, and they were positively correlated with the relative abundance of Fusarium. In addition, levels of ammonium nitrogen (NH₄-N), nitrate nitrogen (NO₃-N), available phosphorus (AP), available potassium (AK), organic matter (SOM), and pH in rhizosphere soil were also significantly related to changes in the microbial community structure. In summary, the application of 6S-2 fertilizer was effective in alleviating some aspects of ARD by promoting plant growth and optimizing the soil microbial community structure.

(1) Background: The cultivation of resistant rootstocks is an effective way to prevent ARD. (2) Methods: 12-2 (self-named), T337, and M26 were planted in replanted and sterilized soil. The aboveground physiological indices were determined. (3) Results: The plant heights and the stem thicknesses of T337 and M26 were significantly affected by ARD. Relative chlorophyll content (June–October), P_n (August–September), and G_s (August) of T337 and relative chlorophyll content (June–July, September), P_n (September–October), and C_i (September) of M26 were significantly affected by ARD. ARD had a significant effect on F_v/F_m (June), qP (June–July), and NPQ of T337 (June–October, except August) and F_v/F_m (June) and NPQ (June-October, except July) of M26. Additionally, ARD affected Rfd of M26 and T337 during August. SOD (August and October), POD (August–September), and CAT (July-August, October) activities and MDA (September–October) content of T338 as well as SOD (July–October), POD (June–October), and CAT (July-October) activities and MDA (July, September–October) content of M26 were significantly affected by ARD. ARD significantly reduced nitrogen (October), phosphorus (September–October), and zinc (July) contents of M26 and potassium (June) content of T337. The above physiological indices were not affected by ARD in 12-2. (4) Conclusions: 12-2 could be useful as an important rootstock to relieve ARD due to strong resistance.

Elaeagnus angustifolia L. is a deciduous tree of the Elaeagnaceae family. It is widely used in the study of abiotic stress tolerance in plants and for the improvement of desertification-affected land due to its characteristics of drought resistance, salt tolerance, cold resistance, wind resistance, and other environmental adaptation. Here, we report the complete genome sequencing using the Pacific Biosciences (PacBio) platform and Hi-C assisted assembly of E. angustifolia . A total of 44.27 Gb raw PacBio sequel reads were obtained after filtering out low-quality data, with an average length of 8.64 Kb. And 39.56 Gb clean reads was obtained, with a sequencing coverage of 75×, and Q30 ratio > 95.46%. The 510.71 Mb genomic sequence was mapped to the chromosome, accounting for 96.94% of the total length of the sequence, and the corresponding number of sequences was 269, accounting for 45.83% of the total number of sequences. The genome sequence study of E. angustifolia can be a valuable source for the comparative genome analysis of the Elaeagnaceae family members, and can help to understand the evolutionary response mechanisms of the Elaeagnaceae to drought, salt, cold and wind resistance, and thereby provide effective theoretical support for the improvement of desertification-affected land.

(1) Background: Cultivating resistant rootstocks is an effective way to mitigate apple replant disease (ARD), and we developed superior apple rootstock line 12-2 (self-named), which shows improved ARD resistance. (2) Methods: We used ARD-associated pathogen Fusarium proliferatum MR5 (MR5) to test the fungal infection in the 12-2 line. Seedlings of the 12-2, T337, and M26 rootstock lines were planted in a substrate with potato dextrose broth and MR5 spore solution, and aboveground physiological indicators were measured. (3) Results: MR5 had the greatest effect on the leaf growth of T337 and M26. The incidence rates of infectious symptoms in the T337 and M26 lines were 68 and 100%, respectively. MR5 significantly affected the leaf chlorophyll content, ETR, and NPQ of T337 and M26, as well as P_n and T_r of M26. MR5 tended to reduce the leaf photosynthetic parameters of T337, but the decreases were not significant. The leaf reactive-oxygen-species levels of T337 and M26, the leaf antioxidant-enzyme activities of M26, and the superoxide-dismutase activity of T337 were significantly affected by MR5. MR5 also had a significant effect on the leaf malondialdehyde, proline, and soluble-sugar contents of T337 and M26. None of these aboveground physiological indicators were affected by MR5 in the 12-2 rootstock. (4) Conclusions: The 12-2 rootstock was more resistant to ARD-associated MR5 and could serve as an important test material for resistant-apple-rootstock breeding in China.