Abstract
Fertilizer practices can significantly impact the fruit quality and microbial diversity of the orchards. The fungi on the surface of fruits are essential for fruit storability and safety. However, it is not clear whether fertilization affects the fungal diversity and community structure on the surface of grape berries. Here, grape quality and the fungal diversity on the surface of grapes harvested from three fertilizer treatments were analyzed shortly after grape picking (T0) and following 8 days of storage (T1). The study involved three treatments: (1) common chemical fertilizer for 2 years (CH); (2) increased organic fertilizer and reduced chemical fertilizer for 1 year (A.O); and (3) increased organic fertilizer and reduced chemical fertilizer for 2 years (B.O). The application of increased organic fertilizer and reduced chemical fertilizer increased the soluble solids content (SSC) of the grape berries and decreased the pH of the grape juice. A total of 827,947 high-quality fungal sequences were recovered and assigned to 527 operational taxonomic units. Members of the Ascomycota phylum were dominant in all samples and accounted for 94.41% of the total number of detected sequences, followed by the Basidiomycota (5.05%), and unidentified fungi (0.54%). Alpha and beta diversity analyses revealed significantly different fungal populations in the three fertilizer treatments over the two time periods. The fungal diversity and richness on the grape berry surface in the B.O and A.O treatments were higher than those in the CH treatment. Among the detected fungi, the B.O treatments were mainly Pichia, Aureobasidium, and Candida genera, while the CH treatments were Botrytis, Aspergillus, and Penicillium. Moreover, significant differences were revealed between the two assessment times (T0 and T1). The samples from the T0 timepoint had higher fungal richness and diversity than the samples from T1 timepoint. Increasing organic fertilizer usage in grape management could improve grape quality and went on to increase the fungal diversity, as well as the relative abundance (RA) of beneficial fungi on grape berry surfaces. The correlation analysis suggested that the pH of the grape juice was significantly negatively correlated with fungal diversity parameters.
Highlights
Increases in global grain and fruit yields in recent decades have been largely dependent on heavy investments in fertilizer (Geng et al, 2019)
We showed that the solids content (SSC) of grape berries treated with organic fertilizer was higher than that of control grapes, and grape berries produced higher total anthocyanin content (TAC) with organic fertilizer (Figure 2)
Increased application of organic fertilizer along with reduced chemical fertilizer for 2 years induced the most significant improve the contents in the SSC and TAC of grape compared to the control grapes from T0 and T1 timepoints
Summary
Increases in global grain and fruit yields in recent decades have been largely dependent on heavy investments in fertilizer (Geng et al, 2019). Many studies have shown that organic fertilization had positive effects on soil microbial richness and diversity (Zhang et al, 2012; Geng et al, 2019). Fungi associated with the winemaking process and grape musts have been extensively documented (Escribano-Viana et al, 2018; Oliveira et al, 2018), few studies have concentrated on the fungal community composition on the table grape berry surface under different fertilizer practices. The paper aimed to investigate the grape quality and the fungal diversity on the grape berry surface under three fertilizer treatments at two postharvest timepoints to provide a theoretical basis for improving the ecological environment and promoting the sustainable production of grapes in arid areas
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