•Alternate partial root-zone irrigation with high frequency increased fruit yield and WUEET.•Evaporation, evapotranspiration and leaf area index were decreased in APRI with high frequency.•APRI with ...high frequency has a great potential for apple production in arid region.
Apple is an important fruit tree in semiarid and arid areas, but increasing water scarcity limits apple productivity. Earlier studies have reported that alternate partial root-zone irrigation (APRI) can increase water use efficiency (WUE), but the effects of APRI with different irrigation frequencies on fruit yield and WUE are still unknown or contradictory. To close this knowledge gap, a two-year field experiment was conducted including two irrigation amounts (400 and 500mm) and three irrigation methods (i.e. conventional irrigation with low frequency, APRI with low and high frequencies) in an apple orchard of the arid region of northwest China. Soil water content, sap flow, soil evaporation, leaf area index (LAI), fruit yield and components, and WUE on the basis of irrigation amount and tree evapotranspiration were evaluated. Results showed that (1) compared with low irrigation amount, high irrigation amount improved apple yield and significantly increased tree evapotranspiration and LAI; (2) in comparison of conventional irrigation, APRI could increase apple yield significantly and reduce tree evapotranspiration, so it enhanced WUE; (3) compared with low frequency, APRI with high frequency could improve apple yield and WUE. Our results demonstrated that alternate partial root-zone irrigation with high irrigation frequency has the potential to increase fruit yield and water use efficiency on the basis of tree evapotranspiration in arid northwest China.
Background: It is expedient to reduce or remove a negative effect of replant disease on new plantations after the old uprooted ones. To solve this problem, it is necessary to carry out the direct ...researches aimed at identifying the reasons for a negative effect of toxic soil conditions on young fruit plantations.
Methods: A vegetative trial, aimed at studying the effect of replant disease on the planted young apple trees after the uprooting of a 34-year-old apple plantation which was grown on the plots after a 50-year-old experimental orchard with apple fertilization systems, was established in spring of 2019. Result: It has been found out in a vegetative trial that the growth of young apple trees weakens considerably in the first two years after planting one-year-old trees. The neutralization of replant disease, when dark grey opodzolic heavy loam soil was fertilized with manure, took place due to enriching it with organic substances. As a result, all the indicators of soil fertility increased and different bio-toxic compounds, which had a negative effect on mineral nutrition of young fruit plants, on their growth process and fruiting, neutralized faster and more intensively.
•Hyperspectral reflectance at canopy-scale of apple-trees was measured using the portable spectroradiometer.•The spectra of apple tree canopy affected by floating dust particles were well ...preprocessed by SNV-FD.•Random frog (Rfrog) was used to extract feature bands for estimating leaf N content in apple-trees.•The combination of SNV-FD, Rfrog and ELM was feasible and reliable for estimating the leaf N content in apple-trees.
Rapid estimation of crop nitrogen (N) status is helpful for achieving precise N fertilizer management, so as to promote the collaborative improvement of yield, quality and N use efficiency. To establish a method for rapidly estimating N status of apple-trees based on hyperspectral remote sensing, a field experiment on apple trees with four levels of N application were conducted in Luochuan, Yan'an, China in 2018 and 2019. Hyperspectral data at apple tree canopy scale were obtained at different phenological stages. The outliers in the dataset were detected by Monte-Carlo cross-validation (MCCV). A total of 15 forms of spectral data were analyzed, including the raw spectrum (RS), Savitzky-Golay (SG) smoothing, normalization by the mean (NME), standard normal transformation (SNV), multiplicative scatter correction (MSC) and their combination with the first-order derivative (FD) or second-order derivative (SD). The results showed that SNV-FD was the best preprocessing method for apple tree canopy spectral data on the Loess Plateau. For SNV-FD data, competitive adaptive reweighted sampling (CARS), successive projection algorithm (SPA), random frog (Rfrog), and partial least squares (PLS) were used to extract feature variables. The feature wavelengths extracted by CARS, SPA and Rfrog were widely distributed in visible and near-infrared (VIS/NIR) range. The feature variables extracted by PLS were fewer, but had a strong interpretation. Based on these feature variables, linear and nonlinear models including partial least squares regression (PLSR), support vector machine (SVM), back-propagation artificial neural network (BPANN), extreme learning machine (ELM) and random forest (RF), were used to establish the prediction model. Among all the models, four nonlinear modeling methods were superior to the linear method. The model by Rfrog-ELM achieved the best results (R2P = 0.843, RMSEP = 2.461 g·kg−1, RPD = 2.508). This study demonstrated that the combination of SNV-FD, Rfrog and ELM was feasible and reliable for estimating the leaf N content in apple-trees on the Loess Plateau, China.
Xylanase plays a key role in degrading plant cell wall during pathogenic fungi infection. Here, we identified a xylanase gene,
from the transcriptome of
and examined its function.
has highly elevated ...transcript levels during the infection process of
, with 15.02-fold increase. Deletion mutants of the gene were generated to investigate the necessity of
in the development and pathogenicity of
. The
deletion mutant considerably reduced the virulence of
in apple leaves and in twigs, accompanied by 41.22% decrease in xylanase activity. In addition, we found that VmXyl2 induces plant cell necrosis regardless of its xylanase activity, whereas promoting the infection of
in apple tissues. The cell death-inducing activity of VmXyl2 dependent on BRI1-associated kinase-1 (BAK1) but not Suppressor of BIR1-1 (SOBIR1). Furthermore, VmXyl2 interacts with Mp2
, a receptor-like kinase with leucine-rich repeat. The results offer valuable insights into the roles of VmXyl2 in the pathogenicity of
during its infection of apple trees.
•The translocation of Cu from apple tree root to aerial parts was limited.•Most accumulated Cu in apple tree was stored in fibrous roots.•The largest proportion of Cu in fibrous roots was bound to ...cell wall.•The accumulated Cu in fibrous root was mainly in phosphate and oxalate forms.•Ralls can be considered as a Cu-tolerant species of apple trees.
Little information is known about the tolerance mechanisms of apple trees growing in soils with excess Cu. This study investigated not only the accumulation and translocation of Cu in the organs of two apple tree cultivars (Fuji and Ralls), but also the detoxification mechanisms of their roots at the cell level. Most accumulated Cu was within apple tree root, especially in the fibrous root, for both cultivars. Compared with Fuji, Ralls had significantly higher Cu concentrations in roots, especially for fibrous roots, while lower concentrations in the aboveground parts. Combining the results from subcellular distribution and chemical forms in the fibrous roots of two apple tree cultivars, more Cu amounts were sequestrated in cell wall and vacuole for Ralls and Cu accumulated in the fibrous root of Fuji had higher in vivo mobility. The results of this study implied that different apple tree cultivars differ in the accumulation, transportation and tolerance to toxic levels of soil Cu, and the chemical forms and subcellular partitioning of Cu in the fibrous roots can elucidate some of the variation of apple trees in Cu sensitivity.
Abstract
Background and Aims
Studying the relationship between phenotypic and genetic variation in populations distributed across environmental gradients can help us to understand the ecological and ...evolutionary processes involved in population divergence. We investigated the patterns of genetic and phenotypic diversity in the European crabapple, Malus sylvestris, a wild relative of the cultivated apple (Malus domestica) that occurs naturally across Europe in areas subjected to different climatic conditions, to test for divergence among populations.
Methods
Growth rates and traits related to carbon uptake in seedlings collected across Europe were measured in controlled conditions and associated with the genetic status of the seedlings, which was assessed using 13 microsatellite loci and the Bayesian clustering method. Isolation-by-distance, isolation-by-climate and isolation-by-adaptation patterns, which can explain genetic and phenotypic differentiation among M. sylvestris populations, were also tested.
Key Results
A total of 11.6 % of seedlings were introgressed by M. domestica, indicating that crop–wild gene flow is ongoing in Europe. The remaining seedlings (88.4 %) belonged to seven M. sylvestris populations. Significant phenotypic trait variation among M. sylvestris populations was observed. We did not observe significant isolation by adaptation; however, the significant association between genetic variation and the climate during the Last Glacial Maximum suggests that there has been local adaptation of M. sylvestris to past climates.
Conclusions
This study provides insight into the phenotypic and genetic differentiation among populations of a wild relative of the cultivated apple. This might help us to make better use of its diversity and provide options for mitigating the impact of climate change on the cultivated apple through breeding.
• MicroRNAs play important roles in the regulation of gene expression in plants and animals. However, little information is known about the action mechanism and function of fungal microRNA-like RNAs ...(milRNAs).
• In this study, combining deep sequencing, molecular and histological assays, milRNAs and their targets in the phytopathogenic fungus Valsa mali were isolated and identified. A critical milRNA, Vm-milR16, was identified to adaptively regulate the expression of virulence genes.
• Fourteen isolated milRNAs showed high expression abundance. Based on the assessment of a pathogenicity function of these milRNAs, Vm-milR16 was found to be a critical milRNA in V. mali by regulating sucrose non-fermenting 1 (VmSNF1), 4,5-DOPA dioxygenase extradiol (VmDODA), and a hypothetical protein (VmHy1). During V. mali infection, Vm-milR16 is downregulated, while its targets are upregulated. Overexpression of Vm-milR16, but not mutated Vm-milR16, significantly reduces the expression of targets and virulence of V. mali. Furthermore, deletion of VmSNF1, VmDODA and VmHy1 significantly reduce virulence of V. mali. All three targets seem to be essential for oxidative stress response and VmSNF1 is required for expression of pectinase genes during V. mali–host interaction.
• Our results demonstrate Vm-milRNAs contributing to the infection of V. mali on apple trees by adaptively regulating virulence genes.
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