Nitrogen (N) is an essential macronutrient limiting plant growth and quality of leaf-vegetable sweetpotato (Ipomoea batatas Lam). The objective of this study was to investigate the effects of N deficiency and re-supply on growth, physiology, and amino acids in sweetpotato. Two leaf-vegetable sweetpotato cultivars, Pushu 53 and Tainong 71, were subjected to three treatments in hydro-culture: 1) N sufficiency, 2) N deficiency, and 3) N deficiency and subsequently with N re-supply. Compared with N sufficiency, N deficiency caused a decrease in vine growth, carotenoid and chlorophyll content (Chlt), root viability, photosynthesis, and nitrate reductase (NR) activity in both cultivars, but to a great extent in Tainong 71. Whereas N deficiency increased root growth and glutamine synthetase (GS) activity in both cultivars, and the increase in ‘Tainong 71’ was more obvious. Re-supply of N recovered the vine growth, root viability, Chlt, photosynthesis, NR, and GS activity, to a greater extent for ‘Pushu 53’ than for ‘Tainong 71’. N deficiency significantly decreased essential amino acids, including lysine, phenylalanince, isoleucine, tryptophane, leucine, and valine contents and nonessential amino acids, consisting of glutamic acid, aspartic acid, glycine, argnine, and proline content in both cultivars. These results indicated that the light leaf color leafy sweetpotato ‘Tainong 71’ is sensitive to the N availability and the dark green leaf color ‘Pushu 53’ is more tolerant to low N, which appear to reflect the differential response of two cultivars to their different adaptability to N availability.
Meng Wei, Aijun Zhang, Hongmin Li, Zhonghou Tang and Xiaoguang Chen
Junhuo Cai, Junjun Fan, Xuying Wei and Lu Zhang
Lycoris radiata has beautiful bright-red flowers with both medicinal and ornamental value. However, the mechanisms underlying an unusual characteristic of Lycoris radiata, flowering without leaves, remain unclear. In this study, climatic influences, biomass composition, and yearly variations in bulb contents across eight developmental stages of L. radiata were analyzed. Thus, L. radiata summer dormancy was investigated in three dimensions: climate-associated phenology, biomass distribution characteristics, and physiologic bulb changes. The results showed that dormancy was most strongly affected by high ambient temperature, followed by scape development, flowering, leafing out, vigorous leaf growth, flower bud differentiation, flower bud predifferentiation, and leaf maturation. Biomass allocation, bulb contents, oxidoreductase activity, and root activity fluctuated significantly in L. radiata among developmental stages. Relative bulb dry weight was greatest during the dormant period (95.95% of total dry weight) and lowest during vigorous leaf growth (November–December). Root biomass was also significantly greater during dormancy than during flowering, leaf maturation, and flower bud differentiation. Only root biomass during vigorous leaf growth was greater than root biomass during dormancy. However, in dormant bulbs, soluble sugar content, soluble protein content, root activity, superoxide dismutase (SOD) activity, and peroxidase (POD) activity decreased. Thus, summer dormancy in L. radiata only constitutes a morphologic dormancy of the aboveground plant; the bulb and root remain physiologically active. The results suggest that L. radiata is sensitive to both ambient temperature and light, and that summer dormancy is triggered by the synergistic stimulation of these two factors. Although temperature controls dormancy, it plays only a limited regulatory role during the L. radiata flowering period. Thus, it is difficult to induce flowering or regulate annual flowering in this species through temperature control alone.
Liping Zhang, Chen Shen, Jipeng Wei and Wenyan Han
6-Benzyladenine (6-BA) is a safe and efficient cytokinin. The adult tea plants of the cv. Longjing 43 were used in this study. The foliar portion of tea bushes were sprayed with different concentrations (50, 100, 200, or 400 mg·L−1) of 6-BA after heavy pruning, when three to four leaves grew out in late May. The effects of 6-BA application on the growth of the new shoots and lateral branches were quantified. After 5 months, treatments with 50, 100, 200, or 400 mg·L−1 6-BA suppressed plant height by 11.0%, 18.0%, 21.0%, or 22.0%, respectively; 6-BA at 100, 200, or 400 mg·L−1 decreased the number of lateral branches by 20.0%, 23.0%, or 18.0%, respectively. Meanwhile, treatments with 50, 200, or 400 mg·L−1 6-BA increased the length of lateral branches by 38.0%, 79.0%, or 81.0% respectively; 200 mg·L−1 6-BA increased the diameter of lateral branches by 8.0%. In addition, after 2 months, 50 or 200 mg·L−1 6-BA did not significantly affect the growth of functional leaves, 50, 100, or 200 mg·L−1 6-BA did not significantly affect photosynthetic rate (Pn) as compared with the control. Furthermore, 200 or 400 mg·L−1 6-BA significantly increased spring tea yield by 28.9% or 13.3%, respectively as compared with the control. In conclusion, 6-BA at the four concentrations promoted dwarfing and the formation of productive lateral branches and increased the spring yield, and 200 mg·L−1 6-BA exerted the best comprehensive effect.
Jin-wei Zhang, Yi-xue Liu, Jin-ping Yu, Wei Zhang, Ya-qiong Xie and Ning-ning Ge
In the early Spring of 2015 and 2016, weed infestation surveys were conducted in areas of cool-season turfgrass Festuca arundinacea Schreb. at 23 sites within Tianjin municipality in northern China. The weed community within turfgrass areas comprised 37 weed species belonging to 14 families. Perennial weeds accounted for 45.9% of the total community of weed species, whereas annual or biennial weeds accounted for 54.1%. Asteraceae was the dominant family (43.2%), and the percentage of broadleaved weeds was 94.6%. Statistical analyses of the weed dominance index (integrating weed relative height and relative coverage) and relative abundance (integrating weed relative density, frequency, and uniformity) showed that the 10 most common weed species during the early spring were Ixeris polycephala Cass., Taraxacum mongolicum Hand.-Mazz., Inula japonica Thunb., Hemistepta lyrata Bge., Trigonotis pedunclaris (Trev.) Benth., Calystegia hederacea Wall., Lepidium apetalum Willd., Plantago asiatica L., Cirsium segetum Bge., and Ixeris sonchifolia Hance. Ixeris polycephala Cass. and T. mongolicum Hand.-Mazz were the most dominant and harmful weed species. Partial correlation analysis (PACA) indicated that the deterioration rate (percentage of bare soil or coverage of plants other than turfgrass) of the turfgrass area was significantly and positively correlated with the total dominance index [(TDI), an index to evaluate the weed infestation severity)] and that the soil organic matter (SOM) and salinity factors were negatively correlated with the TDI. Factors such as soil nutrient conditions (the contents of N, P, and K and the total N), soil physical properties (density and clay content), soil moisture, soil temperature, and soil pH did not correlate significantly with the TDI. We conclude that the deterioration rate was the most important factor influencing weed infestation in the early spring and that SOM and soil salinity might also be important factors. The results of this study can help turfgrass researchers and managers identify the most harmful weed species and integrate management strategies in areas of cool-season turfgrass F. arundinacea Schreb. during early spring in the Tianjin region, China.
Bingqiang Wei, Lanlan Wang, Paul W. Bosland, Gaoyuan Zhang and Ru Zhang
A cytoplasmic male sterility (CMS) system is one of the most efficient ways to produce F1 hybrid seeds in pepper (Capsicum annuum). Restorer-of-fertility (Rf) genes are a critical component within the CMS/Rf system. The inheritance of Rf genes in pepper by joint segregation analysis was examined. The inheritance of Rf genes in the two progenies was controlled by two major additive-dominant epistatic genes and additive-dominant epistasis polygene. The two major genes had high additive effects and dominant effects. In addition, there existed significant epistatic effects between the two major genes. The major genes had high heritability in F2, BC1, and BC2 generations. Also, the fertility restorer characteristic can be selected during early generations of the breeding cycle.
Jian-Feng Geng, Cheng-Song Zhu, Xiao-Wei Zhang, Yan Cheng, Yuan-Ming Zhang and Xi-Lin Hou
Brassica rapa L. ssp. chinensis (L.) Hanelt, known as nonheading chinese cabbage in China, is an important vegetable in eastern Asia and its genetic improvement requires a genetic linkage map. The first genetic linkage map of nonheading chinese cabbage using 112 doubled haploid lines derived from a released F1 hybrid cultivar Shulü between two lines SW-3 and Su-124 was constructed in this paper. One hundred thirty-eight molecular markers were mapped into 14 linkage groups. Among these markers, there were 77 sequence-related amplified polymorphism markers, 27 simple sequence repeat markers, 21 random amplification polymorphic DNA markers, and 13 intersimple sequence repeat markers. Chi-square tests showed that 54 markers are distorted from Mendelian segregation ratios, and the direction of the distortion is mainly toward the maternal parent SW-3. The distortion affects not only the estimation of genetic distance, but also the order of distorted markers on a same linkage group. Given a specific marker order, the authors proposed a multipoint approach to correct the linkage map in an unbiased manner in an F2 population while considering distorted, dominant, and missing markers. A new method was used to correct the linkage map in the doubled haploid population mentioned earlier considering new, distorted, and missing markers. The total length of the corrected linkage map was 1923.75 cM, with an average marker spacing of 15.52 cM. The map will facilitate selective breeding and mapping of quantitative trait loci.
Wanmei Jin, Qiang Zhang, Sunzhong Liu, Qinping Wei, Wanmei Jin, Zongming Cheng, Xiaohui Xue and Tingzhen Yang
Molecular markers are valuable tools in evaluating genetic diversity and fingerprinting plant germplasm. In this report, simple sequence repeat (SSR) markers were used for assessing genetic diversity in 41 dwarf and semidwarf and early flowering apple (Malus sp.) rootstocks. Sixty-two of 112 pairs of SSR primers generated multiple, scorable fragments. The total number of scored bands was 4138 with the polymorphic frequency ranging from 22.0% to 68.6% with a mean value of 58.5% in 737 alleles. The number of alleles per locus ranged from 6 to 19 with an average of 11.9 alleles. Polymorphic information content per locus was ranged from 0.176 to 0.885 with an average value of 0.606. These results suggested a complex genetic background and genetic diversity in these apple rootstocks. Based on three principal components and unweighted pair group mean average (UPGMA) of SSR data, the 41 apple rootstocks were divided into five groups. Group I contained M. xiaojinensis ‘Xiaojinhaitang'. Group II consisted of M. hupehensis var. pingyiensis ‘Pingyitiancha'. Group III contained M. baccata ‘Shandingzi' and its offspring. Group IV was composed of 16 apple rootstocks, including Malling and Malling Merton series from Great Britain; ‘Budagovski 9' from Russia; ‘Polish 22' from Poland; ‘Cornell-Geneva 24' from the United States; and ‘GM.256', ‘Nei Meng 11', ‘MD.001', ‘7734', and ‘7848' from China. Group V consisted of 16 Shao series rootstocks, which were offspring of M. honanensis × M. domestica ‘Ralls Genet'. This research suggests that the breeding can achieve best performance with more robust rootstock if crosses were performed among these five major groups of germplasms rather than within the major groups.
Shutian Tao, Danyang Wang, Cong Jin, Wei Sun, Xing Liu, Shaoling Zhang, Fuyong Gao and Shahrokh Khanizadeh
Lignin is the main component of stone cells, and stone cell content is one of the crucial factors for fruit quality in chinese white pear (Pyrus ×bretschneideri). The lignin biosynthesis pathway is complex and involves many enzymatic reactions. Cinnamate-4-hydroxylase [C4H (EC.220.127.116.11)] is an essential enzyme in lignin metabolism. This study was conducted to investigate the effect of bagging on lignin metabolism during fruit development in chinese white pear. The study showed that bagging had little effect on stone cell content, lignin content, C4H activity, and C4H gene expression and that there was a positive correlation between C4H gene expression and lignin content as well as stone cell content. Moreover, a full-length complementary DNA (cDNA) encoding C4H (PbrC4H, GenBank accession number KJ577541.1) was isolated from chinese white pear fruit. The cDNA is 1515 bp long and encodes a protein of 504 amino acids. Sequence alignment suggested that the deduced protein belongs to the P450 gene family and that C4H might be located subcellularly in the cell membrane. The results indicate that bagging cannot change the lignin and stone cell content significantly and that C4H catalyzes a step in lignin biosynthesis. These findings provide certain theoretical references and practical criteria for improving the quality of chinese white pear.
L.X. Zhang, W.C. Chang, Y.J. Wei, L. Liu and Y.P. Wang
Cryopreservation of pollen from two ginseng species —Panax ginseng L. and P. quinquefolium L.—was studied. Freezing anthers that served as pollen carriers to –40C before liquid N storage affected pollen viability little after liquid N storage. Anther moisture content affected pollen viability significantly when stored in liquid N. The ideal anther moisture content to carry pollen for liquid N storage was 32% to 26% for P. ginseng and 27% to 17% for P. quinquefolium. Viability of pollen from P. quinquefolium anthers with 25.3% moisture content changed little after 11 months of liquid N storage.
Zhiyong Hu, Min Zhang, Qigen Wen, Jie Wei, Hualin Yi, Xiuxin Deng and Xianghua Xu
Seedlessness is of commercial importance in citrus (Citrus L.). Seedless ‘Ougan’ mandarin (C. suavissima) was selected from a bud sport mutation that occurred in ‘Ougan’ mandarin. We analyzed their pollen viability through KI-I2 and FDA staining, and examined the anthers of wild-type (seedy) and seedless mutant ‘Ougan’ mandarin using histological and cytochemical methods to characterize the process of pollen development. No pollen fertility was detected in this mutant. Pollen abortion in anthers of the mutant occurred at the tetrad stage of microspore development, and almost all the tetrads were abnormal. The mutant had heterogeneous microspore populations, including monads, dyads, triads, tetrads, and polyads in the same microsporangium. Pollen grain number per anther of the mutant was 21.9% less than the wild type. Morphology of mature pollen grains using SEM showed that the shape of mature pollen grains from both wild type and mutant is similar, but the microsporangia of the latter contained pollen grains of more variable sizes. At the early mature pollen grain stage, abundant starch grains and lipids appeared in the wild type's pollen, but fewer amounts were observed in the mutant. Moreover, the tapetal cells of the wild type accumulated lipids, but not those of the mutant. Results indicated that the abnormal development of the microspore led to pollen abortion in the mutant, and this could be the reason for its seedlessness. However, the genetic reasons for the aberrant tetrads are not clear and are under investigation.