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  • Author or Editor: Ran Wang x
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‘Akizuki’ (Pyrus pyrifolia Nakai) is a dominant Asian pear cultivar with gradually increasing cultivation area in Shandong province. However, this cultivar is found susceptible to cork spot disorder in recent years. In this study, we explored the physiological-biochemical mechanism of cork spot disorder in pear fruit, and investigated the effectiveness of spraying calcium (Ca), boron (B) solution or prohexadione calcium (P-Ca) on cork spot incidence. Cork spotted fruit had the characteristics of significantly larger fruit size with shorter fruit pedicels. Compared with normal fruit, cork spotted fruit had lower content of total soluble solids, soluble and reducing sugar, and vitamin C. In addition, cork spotted fruit accumulated much higher levels of N and Mg, and lower levels of K and P. However, Ca deficiency was not observed in cork spotted fruit, on the contrary, we determined high concentrations of Ca and free Ca2+ in disordered fruit. At the same time, the ratios of K/Ca, Mg/Ca, and (K+Mg)/Ca were significantly lower in cork spotted fruit as compared with normal fruit. Among all treatments, spraying with 3500 times dilution of P-Ca at 15-day intervals from 30 to 90 days after full bloom showed promise for reducing cork spot incidence in ‘Akizuki’ pear without affecting fruit quality attributes. This research herein reveals the physiological-biochemical characteristic of cork spot disorder, and implicates P-Ca as a potential tool to reduce cork spot incidence in Asian pear cultivar Akizuki.

Free access

Zinc finger–homeodomain (ZF-HD) proteins, a family of plant-specific transcription factors, play an important role in regulating plant growth and development, as well as responses to stress. Although ZF-HDs have been investigated in several model plants, no systematic studies have been reported in apple (Malus ×domestica). In this study, 14 putative ZF-HD genes were identified in the apple genome and characterized using bioinformatics tools. All members harbored complete canonical structures of the ZF-HD motif. Phylogenetic analysis demonstrated that ZF-HD genes in the genome of apple could be classified into four subfamilies, with high intragroup similarities. Gene-structure analysis revealed that although 11 MdZHDs had only one exon, MdZHD6 and MdZHD13 had two exons and MdZHD8 had six exons, suggesting limited variation among the apple ZHD genes. The expression profiles of MdZHD genes revealed their involvement in the growth and development of different tissues. Numerous binding sites for transcription factors, such as MYB, bZIP, and AP2, were found in the promoter region of the putative MdZHD genes. Nearly all putative MdZHDs were predicted to localize in the nucleus. Finally, the expression levels of the MdZHD genes under abiotic stress were examined in apple rootstock Malus hupehensis and the results showed that the expression of 10 MdZHD genes was induced in response to three abiotic stress factors. Exceptionally, the expression of MdZHD11 was not induced in response to any of the abiotic stress treatments, MdZHD12 was only induced in response to salt stress, and MdZHD7 and MdZHD9 were induced in response to both drought and salt stress. The present results provide valuable insights into the putative physiological and biochemical functions of MdZHDs in apple.

Open Access

The effects of CaCl2, GA3, and H2O2 priming on Isatis indigotica Fort. seed germination characteristics, seedling growth parameters, and antioxidant enzyme activities under salt stress were investigated. NaCl had an adverse effect on the germination and seedling performance of I. indigotica. However, these three priming agents alleviated salt stress by increasing the germination percentage, improving seed vigor, accelerating germination velocity, and establishing strong seedlings. The optimal concentrations were 15 g/L for CaCl2, 0.2 g/L for GA3, and 40 mm for H2O2. Seed priming treatments enhanced the activities of antioxidant enzymes in seedlings, such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), under a salt environment, which reduced the oxidative injury caused by salt. Seed priming is a promising technique that can enhance the ability of I. indigotica seed germination when salt is present.

Open Access

Apple replant disease (ARD) has been reported in all major fruit-growing regions of the world and is often caused by biotic factors (pathogen fungi) and abiotic factors (phenolic compounds). Soil chemical fumigation can kill soil pathogenic fungi; however, the traditionally used fumigant methyl bromide has been banned because of its ozone-depleting effects. There is thus a need to identify greener fumigant candidates. We characterized the effects of different fumigants on the replanted soil environment and the growth characteristics of Malus hupehensis Rehd. seedlings. All five experimental treatments [treatment 1 (T1), metham-sodium; treatment 2 (T2), dazomet; treatment 3 (T3), calcium cyanamide; treatment 4 (T4), 1,3-dichloropropene; and treatment 5 (T5), methyl bromide] promoted significantly the biomass, root growth, and root respiration rate of M. hupehensis seedlings and the ammonium nitrogen (NH4 +-N) and nitrate nitrogen (NO3 -N) contents of replanted soil. Metham sodium (T1) and dazomet (T2) had stronger effects compared with 1,3-dichloropropene (T4) and calcium cyanamide (T3). At 172 days after T1, the height, root length, and root respiration rate of Malus hupehensis Rehd. seedlings, and the NH4 +-N and NO3 -N contents of replanted soil increased by 91.64%, 97.67%, 69.78%, 81.98%, and 27.44%, respectively, compared with the control. Thus, dazomet and metham sodium were determined to be the optimal fumigants for use in practical applications.

Open Access

The relationship between soil texture and the degree of apple replant disease (ARD) was analyzed from the perspective of the microbial community structure and diversity within the rhizosphere soil of Malus hupehensis Rehd. seedlings. Three different textured soils were taken from different apple orchards in Laizhou, Yantai. The soils were divided into two parts, one was kept in replanted conditions, and the other was fumigated with methyl bromide to act as a high standard control. The strength of ARD occurrence was examined by measuring fresh and dry weight suppression (%) of the M. hupehensis seedlings. Differences in the fungal community structure (especially in Fusarium) among the three soil texture types were analyzed using high-throughput sequencing. The results showed that replanted loam clay soil had the highest fungal diversity, followed by sandy loam soil and finally loam soil. The richness of fungi between soil textures, however, was not significantly different. At the genus level, the relative abundance of Fusarium was 1.96%, 0.78%, and 10.89% in replanted sandy loam, replanted loam soil, and replanted loam clay soil, respectively. Moreover, the gene copy number of Fusarium oxysporum, Fusarium solani, and the inhibition rate of fresh weight of M. hupehensis seedlings were the same in the three soil textures. The plant height, photosynthesis (net) (Pn), and stomatal conductance (g S) of the M. hupehensis seedlings were significantly less in the replanted soil compared with the control treatments, with the overall difference being greatest in replanted loam clay soil, followed by replanted sandy loam and then replanted loam soil.

Open Access