Loquat [Eriobotrya japonica (E. japonica)], a small genus of the subtribe Malinae that consists of ≈30 species, is an evergreen rosaceous fruit tree that is native to southeastern China, and some wild species that possess novel, favorable traits have excellent breeding potential. For example, Eriobotrya bengalensis blooms in late spring and ripens in early autumn in Guizhou Province, China, which prevents cold injury in winter by breeding spring-flowering cultivars using the special characters. Therefore, in the present study, the pollination treatments of cut-style pollination were evaluated that may promote successful distant hybridization in Eriobotrya japonica ‘Dawuxing’ × Eriobotrya deflexa and E. japonica ‘Dawuxing’ × E. bengalensis. The results indicated that the impairment of the pollen tube growth in the upper third of the style after pollen germination is an important factor leading to the failure of distant hybridization between the species tested in E. japonica, and that cut-style pollination can effectively overcome prefertilization barriers of the distant hybridization combination. Furthermore, the results of allele-specific polymerase chain reaction (AS-PCR) showed that S-genotypes, in accordance with the S-RNase heredity to separate the rule completely in offspring, should be both parents' S-RNase, and that the random 50 seedlings of Eb-2 and Ed-2 are true hybrids.
Qin Yang, Er Liu, Yan Fu, Fuqiang Yuan, Tingting Zhang and Shu Peng
After nearly a decade of development, the scale of blueberry (Vaccinium sp.) cultivation has increased, particularly in south China; however, this region is becoming increasingly challenged by temperature changes during the flowering phenophase. Understanding the effects of temperature on pollen germination and pollen tube growth in blueberry is thus important. Using the rabbiteye blueberry (V. ashei) ‘Brightwell’, different temperature treatments were carried out during open pollination and cross-pollination with the pollen from rabbiteye blueberry ‘Gardenblue’ in field, greenhouse, and controlled temperature experiments over two consecutive years. The differences in pollen germination, pollen tube dynamics, and ovule viability following different treatments were analyzed, and the critical temperatures were calculated using quadratic and modified bilinear equations to quantify the developmental responses to temperature. The results showed that the fruit set of the artificially pollinated plants inside the greenhouse was significantly higher than that outside the greenhouse. Furthermore, pollen germination and pollen tube growth gradually accelerated under the appropriate high-temperature range, resulting in reduced pollen tube travel time to the ovule. However, the percentage of the style traversed by the pollen tube did not increase at temperatures greater than 30 °C, and a high-temperature range could accelerate ovule degeneration. Therefore, impairment of pollen tube growth in the upper half of the style following pollen germination and ovule degeneration constituted important factors leading to reduced fruit setting under short periods of high temperature during the flowering phenophase in rabbiteye blueberry. This work advances our understanding of the effect of temperature on pollen germination, pollen tube growth, ovule longevity, and fruit setting in rabbiteye blueberry, and provides a foundation for continued cultivation and breeding enhancement. The findings propose that the tolerance of rabbiteye blueberry to a certain high-temperature range in the flowering phenophase should inform breeding strategies for temperature resistance and that temperature range is also an important indicator of suitable environments for cultivation to mitigate potential temperature stress.
Dalong Zhang, Yuping Liu, Yang Li, Lijie Qin, Jun Li and Fei Xu
Although atmospheric evaporative demand mediates water flow and constrains water-use efficiency (WUE) to a large extent, the potential to reduce irrigation demand and improve water productivity by regulating the atmospheric water driving force is highly uncertain. To bridge this gap, water transport in combination with plant productivity was examined in cucumber (Cucumis sativus L.) grown at contrasting evaporative demand gradients. Reducing the excessive vapor pressure deficit (VPD) decreased the water flow rate, which reduced irrigation consumption significantly by 16.4%. Reducing excessive evaporative demand moderated plant water stress, as leaf dehydration, hydraulic limitation, and excessive negative water potential were prevented by maintaining water balance in the low-VPD treatment. The moderation of plant water stress by reducing evaporative demand sustained stomatal function for photosynthesis and plant growth, which increased substantially fruit yield and shoot biomass by 20.1% and 18.4%, respectively. From a physiological perspective, a reduction in irrigation demand and an improvement in plant productivity were achieved concomitantly by reducing the excessive VPD. Consequently, WUE based on the criteria of plant biomass and fruit yield was increased significantly by 43.1% and 40.5%, respectively.
An Qin, Xiaosan Huang, Huping Zhang, Juyou Wu, Jie Yang and Shaoling Zhang
Ascorbic acid (AsA) is a major antioxidant and redox buffer in plants. Dehydroascorbate reductase (DHAR; EC 220.127.116.11) catalyzes the conversion of dehydroascorbate (DHA) to AsA and is crucial for AsA regeneration. In this study, we developed transgenic tomato plants that overexpressed PbDHAR2 to investigate whether PbDHAR2 could limit the deleterious effects of salt and chilling stresses. These transgenic plants contained significantly higher AsA levels than the wild-type (WT) plants. Overexpression of PbDHAR2 increased the expression of the AsA-glutathione (GSH) cycle genes in transgenic lines under salt and chilling stresses. In addition, the transgenic lines subjected to salt and chilling stresses showed higher levels of antioxidant enzyme activity, lower malondialdehyde (MDA) levels, and higher chlorophyll contents than the WT. Thus, our results demonstrate that the regulation of PbDHAR2 during AsA regeneration contributes to enhanced salt and chilling tolerance in tomato.
Nian Wang, Zhang Chang Qin, Jun-bo Yang and Jing-li Zhang
Rhododendron delavayi Franch. is an important ornamental plant and often plays a role in natural hybridization with other sympatric species in Rhododendron subgenus Hymenanthes. Fifteen microsatellite loci were developed and characterized in this species. The average allele number of these microsatellites was four per locus, ranging from three to six. The ranges of expected (HE) and observed (HO) heterozygosities were 0.0365 to 0.7091 and 0.0263 to 0.9512, respectively. Cross-species amplification in R. agastum and R. decorum showed that a subset of these markers holds promise for congeneric species study. These sets of markers are potentially useful to investigate the genetic structure and gene flow of R. delavayi and other congeneric species.
Yuan Huang, Xue-qin Wang, Chun-yan Yang and Chun-lin Long
Primula amethystina Franchet. is a beautiful perennial herbaceous plant locally endemic to the alpine area in southwest China. We isolated and characterized 11 polymorphic microsatellite primer pairs from this species. The number of alleles ranged from two to five. The observed and expected heterozygosities (HO and HE) were 0.25 to 0.875 and 0.223 to 0.691, respectively. Six loci were significantly deviated from Hardy-Weinberg equilibrium as a result of the heterozygote deficiency. These markers will have great potential to reveal the genetic population structure and genetic diversity of P. amethystina.
Yuejin Weng, Jun Qin, Stephen Eaton, Yufeng Yang, Waltram Second Ravelombola and Ainong Shi
Cowpea [Vigna unguiculata (L.) Walp] is an annual legume crop grown worldwide to provide protein for human consumption and animal feed. The objective of this research was to evaluate the seed protein content in U.S. Department of Agriculture (USDA) cowpea germplasm for use in cowpea breeding programs. A field experiment was conducted with a randomized complete block design (RCBD) with three duplications in two locations, Fayetteville and Alma, in Arkansas, United States. A total of 173 USDA cowpea accessions were evaluated with the Elementar Rapid N analyzer III for their seed protein contents. The results showed that there was a wide range of seed protein content among the 173 cowpea genotypes, ranging from 22.8% to 28.9% with an average of 25.6%. The broad-sense heritability for seed protein among the 173 cowpea genotypes was 50.8%, indicating that seed protein content was inheritable and can be selected in breeding processing. The top five cowpea accessions with the highest seed protein contents were USDA accession PI 662992 originally collected from Florida (28.9%), PI 601085 from Minnesota (28.5%), and PI 255765 and PI 255774 from Nigeria and PI 666253 from Arkansas (28.4% each). PI 339587 from South Africa had the lowest protein content with 21.8%. The were also significant differences in seed protein contents observed among different seedcoat colors; the accessions with cream color exhibited higher protein content (27.2%) than others. This research could provide information for breeders to develop cowpea cultivars with higher seed protein content in a cowpea breeding program.
Qin Yang, Yan Fu, Yalan Liu, Tingting Zhang, Shu Peng and Jie Deng
The xenia effect refers to the phenomenon whereby the pollen genotype directly affects seed and fruit development during the period from fertilization to seed germination, which leads to different characteristics in phenotypic traits. The xenia effect can create differences in the endosperm and embryo formed after double fertilization and can also alter various fruit parameters, such as the fruit-ripening period; the fruit shape, size, and color; the flavor quality, such as sugars and acids; as well as the nutrient quality, such as anthocyanins. The xenia effect manifests in various ways, playing an important role in increasing the yield of fruit trees, improving fruit appearance and internal quality, as well as in directional breeding. Compared with other pomology research areas, our understanding of the xenia effect is still in its infancy. Currently, xenia is classified into two types: xenia and metaxenia. In the former, the direct effects of the pollen genotype are exhibited in the syngamous parts of the ovules; that is, the embryo and endosperm only. In the latter, the effects of the pollen genotype are demonstrated in structures other than the embryo and endosperm; that is, in tissues derived wholly from the mother plant material, in seed parts such as the nucellus and testa, as well as in the carpels and accessory tissues. However, the current classification has various shortcomings. In the present study, we propose a novel classification based on whether the appearance of xenia results from the tissue formed by double fertilization. Three xenia types are proposed: double-fertilization xenia, non–double-fertilization xenia, and combined xenia. The new classification has great theoretical and practical significance for future studies on the xenia effect and its mechanisms and also provides a more effective, broader application of xenia in improving the yield and quality of fruit trees.
Tonghua Pan, Juanjuan Ding, Gege Qin, Yunlong Wang, Linjie Xi, Junwei Yang, Jianming Li, Jing Zhang and Zhirong Zou
During the autumn/spring “off” season, yield and quality of tomatoes are often affected by insufficient CO2 and low light in greenhouse production. Although tomato is one of the most widely cultivated vegetables, few studies have investigated the interactive effects of supplementary light and CO2 enrichment on its growth, photosynthesis, yield, and fruit quality in greenhouse production. This study investigates the effects of supplementary light (200 ± 20 μmol·m–2·s–1) and CO2 enrichment (increases to about 800 μmol·mol–1), independently and in combination, on these parameters in autumn through spring tomato production. Compared with tomatoes grown under ambient CO2 concentrations and no supplementary light (CaLn), supplementary light (CaLs) and supplementary light and CO2 enrichment (CeLs) significantly promoted growth and dry weight accumulation. Meanwhile, CO2 enrichment (CeLn) and CaLs significantly improved photosynthetic pigment contents and net photosynthetic (Pn) rates, whereas CeLs further improved these and also increased water use efficiency (WUE). CeLn, CaLs, and CeLs significantly increased single fruit weight by 16.2%, 28.9%, and 36.6%, and yield per plant by 19.0%, 35.6%, and 60.8%, respectively. The effect of supplementary light on these parameters was superior to that of CO2 enrichment. In addition, CaLs and CeLs improved nutritional quality significantly. Taken together, CeLs promoted the greatest yield, WUE, and fruit quality, suggesting it may be a worthwhile practice for off-season tomato cultivation.
Lingdi Dong, Waltram Ravelombola, Yuejin Weng, Jun Qin, Wei Zhou, Gehendra Bhattarai, Bazgha Zia, Wei Yang, Linqi Shi, Beiquan Mou and Ainong Shi
Previous investigations showed that accumulations of Na+ and Cl− in leaves resulted in reductions in chlorophyll content, thereby affecting photosynthesis. Understanding how chlorophyll content evolves over time will help plant breeders to select cowpea genotypes with better tolerance to salinity by allowing them to choose those with more stable chlorophyll content under salt stress. The objective of this study was to assess how the chlorophyll content of cowpea genotypes changed over the course of 24 d of salt stress at the seedling stage. A total of 24 cowpea genotypes with different salt responses were used in this study. The experiment used a split-plot design with salt treatment as the main plot and cowpea genotypes as the subplot. In the main plot, there were two salt treatments: 0 mm (ionized water) and 200 mm NaCl. In the subplot, the cowpea genotypes were arranged as a completely randomized design with three replicates per genotype. The results revealed that: a1) the time × genotype interaction was significant under conditions with and without salt; 2) chlorophyll content slowly decreased in the salt-tolerant genotypes; 3) chlorophyll content slightly increased on day 6 and day 9 of salt stress in both moderate and sensitive genotypes, but it decreased at a faster rate than in the salt-tolerant genotypes; and 4) salt-sensitive genotypes were completely dead on day 24 of salt stress, whereas the salt-tolerant genotypes were able to maintain a significant amount of chlorophyll content. These results can be used to advance breeding programs for salt tolerance in cowpea.