PbrARF4 contributes to calyx shedding of fruitlets in ‘Dangshan Suli’ pear by partly regulating the expression of abscission genes

Fruitlet calyx shedding in pear plants is apparently regulated via numerous pathways that involve both environmental triggers and phytohormones cues such as auxin. In this study, we found at 10 days after full bloom (DAFB) higher levels of indoleacetic acid (IAA) and tryptophan (Trp) in calyx persistence fruitlet (CPF) than calyx shedding fruitlet (CSF) ofDanshan Suli’ pear (Pyrus bretschneideri Rhed.). Consisting with this, the activity of indolealdehyde oxidase (IAAIdO), which promotes IAA synthesis, was remarkably increased, and that of peroxidase(POD), which degrades IAA, dropped markedly in CPF but not in CSF. Further, qRT-PCR results revealed that most of 31 PbrARFs (encoding auxin response factors) in Pyrus bretschneideri were highly expressed in CPF, whereas PbrARF4, PbrARF24 and PbrARF26 were significantly downregulated in CPF vis-a-vis CSF. Phylogenetic analysis revealed that 6 PbrARFs clustered in the group III, where PbrARF4 showed the closest affinity with AtARF1 that promotes organ abscission, indicating a putative role of PbrARF4 in mediating the process of calyx shedding in pear. In fact, the ectopic overexpression of PbrARF4 in Solanum lycopersicum resulted in an earlier-formed and deeper abscission layer (AL) in the transgenic plants, whose calyxes were more prone to wilt at the mature red stage (MR) compared with the control plants (wild-type). More importantly, expression levels of the abscission genes SILS and Sl Cel2 in transgenic plants overexpressing PbrARF4 were significantly upregulated in comparation with the WT, whereas those of Sl BI and Sl TAPG2 were considerably inhibited. Further, PbrJOINTLESS and PbrIDA,the two genes related to calyx shedding in pear, were up-regulated more in CSF than CPF. The findings contribute to a better understanding of PbrARFs involved in fruitlet calyx shedding of pear, which could prove beneficial to improving the quality of pear fruit.

Mulching broad ridges with a woven polypropylene fabric increases the growth and yield of young pear trees ‘Yuluxiang' in the North China Plain

Unlike traditional ridging, mulching broad ridges with a woven polypropylene fabric (WPF) can reduce soil evaporation during the drought season and avoid long saturation time in the root zone of pear trees during the rainy season. In this study, field experiments were conducted from 2017 to 2020 in a pear orchard in the North China Plain to investigate the effects of mulching broad ridges (0.3 m in height and 2 m in width) with WPF on soil temperature and moisture, nitrogen leaching, vegetative and reproductive growth of young pear trees(Pyrus bretschneideri Rehd.‘Yuluxiang’). The experiments involved two treatments, namely, control (traditional no-ridge planting without mulching) and mulching broad ridges with WPF (RM treatment). The results showed that the RM treatment increased soil moisture and temperature and decreased nitrogen leaching, resulting in vigorous growth of the young pear trees. Moreover, the RM treatment increased the tree trunk cross-sectional area and height of the young pear trees by 37%and 8%in 2020, respectively. The nitrate nitrogen content at the soil layer depth of 0-30 cm was significantly higher in the RM than that in control. Furthermore, the RM treatment significantly increased the fruit yield due to larger tree size. In addition, compared with control, significantly higher fruit soluble solid content of RM treatment was detected in 2020. High precipitation (423 mm) occurred during fruit enlargement stage in 2020, RM treatment decreased the rainfall infiltration in the ridge and the soil moisture in root region, resulting in the improvement of fruit quality, compared with control.Therefore, mulching broad ridges with WPF can be implemented to increase soil moisture during drought season, soil temperature, and nitrate nitrogen content, thereby improving the growth and fruit yield of young pear trees. Additionally, it can reduce soil moisture in the root zone during the rainy season and improve the fruit quality of the trees. Finally, it can reduce nitrate nitrogen leaching, thereby reducing environmental pollution.

黄冠梨果实中氨基酸及矿质元素分析与评价

为了探明黄冠梨(Pyrus bretschneideri Rehd.cv.Huangguan)果实中氨基酸和矿质元素组成特点,以武威市20个具有代表性果园的黄冠梨果实为材料,利用高效液相色谱和原子吸收光谱法等对其17种氨基酸和11种矿质元素指标进行测定与分析,并采用氨基酸比值、氨基酸比值系数和氨基酸比值系数分等营养学方法进行氨基酸营养价值评价。结果显示:黄冠梨果实中氨基酸种类齐全,被检测的17种氨基酸均存在,其中包括除色氨酸之外的7种必需氨基酸。氨基酸总量为90.55~142.90 mg/100 g,天冬氨酸、丝氨酸、谷氨酸和赖氨酸4种氨基酸是其主要氨基酸;其中必需氨基酸、半必需氨基酸和药用氨基酸含量分别占氨基酸总量的23.78%、6.13%和57.24%。必需氨基酸含量分别占氨基酸总量、非必需氨基酸总量的27.38%、31.20%,均低于WHO/FAO模式参考值;氨基酸比值系数SRC值为28.74,第一限制氨基酸是异亮氨酸,其他氨基酸含量均偏离模式蛋白含量,氨基酸营养价值中等。果实矿质元素含量范围为1883.42~2623.75 mg/kg,其中K、N、P、Ca和Mg等5种大量元素含量高,占矿质元素总量的99.46%,而Fe、Na、Cu、Zn等6种微量元素含量很低。基于氨基酸和矿物质元素的分析结果,黄冠梨氨基酸种类齐全、营养价值中等,且矿质元素含量丰富,具有较高的保健和药用功能,为其进一步开发利用提供科学依据。