The effects of crop rotation combinations on the soil quality of old apple orchard

This study investigated the effects of six crop rotation combinations on the soil quality of old apple orchard and seedling growth of Malus hupehensis Rehd. (apple rootstock) under pot conditions. The inhibitory effects of crops such as Allium fistulosum, Brassica juncea, and Triticum aestivum on four species of Fusarium were observed and compared in six treatments. These were continuous cropping (CK), fumigation with the methyl bromide (FM), rotating A. fistulosum only (R1), rotating A. fistulosum and T. aestivum (R2), rotating A. fistulosum, B. juncea, and T. aestivum (R3), and fallow (FC) in a year. The results showed that the biomass of Malus hupehensis Rehd. seedlings increased significantly. The root length increased and the root architecture was optimized. The respiration rate of the root system was increased by about 1 time after rotation. The treatments of R1, R2, R3, and FC increased bacterial count by 232.17%, 96.04%, 316.21%, and 60.02%, respectively. However, the fungi were reduced in varying degrees and bacteria/fungi ratio was increased by 5–10 times. The enzyme activities, pH, and organic matter were increased, but soil bulk density was decreased. Phenolic acids such as phloridzin was decreased significantly. The copy number of four Fusarium species declined by 85.59%, 74.94%, 69.68%, and 54.41% after rotating three different crops (R3 treatment). The root volatiles of three plants inhibited mycelial growth and spore germination of four Fusarium species

Effects of Soil Texture on the Growth of Young Apple Trees and Soil Microbial Community Structure Under Replanted Conditions

ABSTRACT: A two-year field experiment was carried out in order to study the occurrence degree and mechanism of apple replant disease (ARD) in the apple orchards with different soil textures. So we can adopt appropriate control measures according to the severity of ARD. Healthy two-year-old seedlings with consistent growth were selected, of which the root stock was T337 and the scion was Yanfu 3. There were significant differences in biomass between methyl bromide fumigation and replanted treatments, and the difference was the largest in clay loam, followed by sandy loam, and loam, which verified ARD in clay loam was most serious, followed by sandy loam and loam. Based on high-throughput sequencing of fungi in soil samples, fungal richness and diversity were the highest in clay loam, followed by sandy loam, and loam. The relative abundance of Fusarium in SX, SL, FX, FL, WX and WL was 7.33%, 19.32%, 2.70%, 4.24%, 10.71% and 23.87%, respectively. Based on Real-time quantitative analysis, there were significant differences in the number of Fusarium oxysporum and Fusarium solani between methyl bromide fumigation and replanted treatments, i.e., clay loam > sandy loam > loam. Fusarium was the main pathogen causing ARD. This shows that ARD is the most serious under replanted clay loam condition. High-throughput sequencing technology was used to prove the difference in Fusarium was one of the important reasons for ARD under different soil textures. This technology provides a new idea for the prevention and control of ARD

Analysis of the Fungal Community in Apple Replanted Soil Around Bohai Gulf

Apple replant disease (ARD) is a frequently occurring plant disease in replanted orchards around Bohai Gulf, which causes growth inhibition and even death of plants. The aim of this study was to investigate the etiology of ARD around Bohai Gulf. In this study, the primary growth inhibition of apple seedlings was evaluated in ten replanted soils, sampled around Bohai Gulf. A fungal clone library was used to identify changes in the structure and composition of the soil fungal community. The results revealed that the Simpson diversity indices of Laizhou and Pulandian orchards were higher than others, presenting severe ARD. Ascomycota dominated around Bohai Gulf at the phyla level. Fusarium and Saccharomyces were abundant in all replanted soils. In addition, correlations between the relative abundance of fungal genera in soils and the severity of ARD were analyzed. The results showed that Fusarium was correlated positively with the severity of ARD, but Mortierella was negatively correlated. Furthermore, the quantitative PCR of Fusarium oxysporum, which was regarded as a factor of ARD, was performed. Overall, this study demonstrated that ARD was strongly associated with an unbalanced microbial ecosystem with more pathogenic fungi, while Fusarium in the apple replanted soil was the key factor for ARD around Bohai Gulf. Keywords: apple, replanted disease, Fungi clone library, fusarium, fungal communit