Abstract
BackgroundBrowning spot (BS) disorders seriously affect the appearance quality of ‘Huangguan’ pear and cause economic losses. Many studies on BS have mainly focused on physiological and biochemical aspects, and the molecular mechanism remains unclear.ResultsIn the present study, the structural characteristics of ‘Huangguan’ pear with BS were observed via scanning electron microscopy (SEM), the water loss and brown spots were evaluated, and transcriptomic and metabolomics analyses were conducted to reveal the molecular mechanism underlying ‘Huangguan’ pear skin browning disorder. The results showed that the occurrence of BS was accompanied by a decrease in the wax layer and an increase in lignified cells. Genes related to wax biosynthesis were downregulated in BS, resulting in a decrease in the wax layer in BS. Genes related to lignin were upregulated at the transcriptional level, resulting in upregulation of metabolites related to phenylpropanoid biosynthesis. Expression of calcium-related genes were upregulated in BS. Cold-induced genes may represent the key genes that induce the formation of BS. In addition, the results demonstrated that exogenous NaH2PO4·2H2O and ABA treatment could inhibit the incidence of BS during harvest and storage time by increasing wax-related genes and calcium-related genes expression and increasing plant resistance, whereas the transcriptomics results indicated that GA3 may accelerate the incidence and index of BS.ConclusionsThe results of this study indicate a molecular mechanism that could explain BS formation and elucidate the effects of different treatments on the incidence and molecular regulation of BS.
Highlights
Browning spot (BS) disorders seriously affect the appearance quality of ‘Huangguan’ pear and cause economic losses
There are many pear varieties planted in China, and the main species cultivated for commercial production include sand pear (P. pyrifolia Nakai), ussurian pear (P. ussuriensis Maxim), white pear (P. bretschneideri Rehd), and Xinjiang pear (P. sinkiangensis Yu), as well as interspecific hybrid types [2]
Paraffin section observations revealed that the degree of lignification of the exocarp cells of the BS parts was significantly higher than that of the normal parts (Fig. 1C, D)
Summary
Browning spot (BS) disorders seriously affect the appearance quality of ‘Huangguan’ pear and cause economic losses. ‘Huangguan’ pear (Pyrus bretschneideri × Pyrus pyrifolia) is an early- and medium-maturing cultivar widely planted in northern China that has a high-quality and exquisite appearance after bagging [3]. This fruit has many excellent characteristics, such as a beautiful appearance, strong resistance, early fruit bearing and high yield in successive years, which are traits that are desired by the majority of producers and consumers. Whole fruit browning may occur in the later stages of this disease This disorder affects only the exocarp of pear fruit, and the flesh and core are not affected [6]. BS disorder is known as chickenclaw disease by orchardman in China, and it causes a significant decrease in the commercial value of fruit for fruit farmers [7]
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