Genome-wide analysis of expression quantitative trait loci(eQTLs)reveals the regulatory architecture of gene expression variation in the storage roots of sweet potato

Dissecting the genetic regulation of gene expression is critical for understanding phenotypic variation and species evolution.However,our understanding of the transcriptional variability in sweet potato remains limited.Here,we analyzed two publicly available datasets to explore the landscape of transcriptomic variations and its genetic basis in the storage roots of sweet potato.The comprehensive analysis identified a total of 724,438 high-confidence single nucleotide polymorphisms(SNPs)and 26,026 expressed genes.Expression quantitative trait locus(eQTL)analysis revealed 4408 eQTLs regulating the expression of 3646 genes,including 2261 local eQTLs and 2147 distant eQTLs.Two distant eQTL hotspots were found with target genes significantly enriched in specific functional classifications.By combining the information from regulatory network analyses,eQTLs and association mapping,we found that IbMYB1-2 acts as a master regulator and is the major gene responsible for the activation of anthocyanin biosynthesis in the storage roots of sweet potato.Our study provides the first insight into the genetic architecture of genome-wide expression variation in sweet potato and can be used to investigate the potential effects of genetic variants on key agronomic traits in sweet potato.

Overexpression of phosphatidylserine synthase IbPSS1 affords cellular Na+homeostasis and salt tolerance by activating plasma membrane Na^(+)/H^(+)antiport activity in sweet potato roots

Phosphatidylserine synthase(PSS)-mediated phosphatidylserine(PS)synthesis is crucial for plant development.However,little is known about the contribution of PSS to Na^(+)homeostasis regulation and salt tolerance in plants.Here,we cloned the IbPSS1 gene,which encodes an ortholog of Arabidopsis AtPSS1,from sweet potato(Ipomoea batatas(L.)Lam.).The transient expression of IbPSS1 in Nicotiana benthamiana leaves increased PS abundance.We then established an efficient Agrobacterium rhizogenes-mediated in vivo root transgenic system for sweet potato.Overexpression of IbPSS1 through this system markedly decreased cellular Na^(+)accumulation in salinized transgenic roots(TRs)compared with adventitious roots.The overexpression of IbPSS1 enhanced salt-induced Na^(+)/H^(+)antiport activity and increased plasma membrane(PM)Ca^(2+)-permeable channel sensitivity to NaCl and H2O2 in the TRs.We confirmed the important role of IbPSS1 in improving salt tolerance in transgenic sweet potato lines obtained from an Agrobacterium tumefaciens-mediated transformation system.Similarly,compared with the wild-type(WT)plants,the transgenic lines presented decreased Na^(+)accumulation,enhanced Na^(+)exclusion,and increased PM Ca^(2+)-permeable channel sensitivity to NaCl and H2O2 in the roots.Exogenous application of lysophosphatidylserine triggered similar shifts in Na^(+)accumulation and Na^(+)and Ca^(2+)fluxes in the salinized roots of WT.Overall,this study provides an efficient and reliable transgenic method for functional genomic studies of sweet potato.Our results revealed that IbPSS1 contributes to the salt tolerance of sweet potato by enabling Na^(+)homeostasis and Na^(+)exclusion in the roots,and the latter process is possibly controlled by PS reinforcing Ca^(2+)signaling in the roots.

Inheritance Tendency of Storage Root Quality Traits in F_1 Hybrids of ‘Xushu 25'and ‘Xu 22-5'

＇ Xushu 25＇ , ＇ Xu 22-5＇ and their reciprocal F1 hybrids were used as experimental materials to analyze the inheritance tendency of storage root quality traits of sweetpotato. The results showed that most of the storage root traits in F~ hybrids of ＇ Xushu 25 ＇ and ＇ Xu 22-5 ＇ were quantitative traits controlled by multi- pie genes. The carotenoid content in fresh storage roots of F1 hybrids was lower than that of parents, with the average genetic transmitting ability and average coeffi- cient of variation at 51.17% and 103.21%, respectively. The starch content in fresh storage roots reached mid-parent level, with the average genetic transmitting ability at 96.66%. The reducing sugar content in fresh storage roots of F, hybrids tended to be polarized; to be specific, most of the Ft hybrids exhibited higher re- ducing sugar content than their parents with high reducing sugar content or exhibited lower reducing sugar content than their parents with low reducing sugar content, but F~ hybrids with reducing sugar content ranging between that of their parents accounted for a small proportion. The soluble sugar content in fresh storage roots reached mid-parent level and tended to be lower than parents, with the average genetic transmitting ability and average coefficient of variation at 82.25% and 21.93%, respectively. The crude protein content in fresh storage roots of FI hybrids exceeded mid-parent level and tended to increase; positive-crossing and negative-crossing progenies exhibiting higher crude protein content than their parents with high crude protein content accounted for 15.53% and 16. 28%, respectively.

Pesticides Could Alleviate the Symptoms of Sweet Potato Virus Disease(SPVD)

In recent years, sweet potato virus disease （SPVD） has severely affected the production of sweet potato in China. In order to select chemical agents to prevent sweet potato from being infected with SPVD, 14 pesticides were sprayed on the plants of sweet potato infected with SPVD, and the relative mRNA level of the viruses in the leaves and physiological indicators of sweet potato plants were detected. The results showed that after the application of most of the pesticides, the relative mRNA level of the two viruses that caused SPVD decreased, and the chlorophyll content and biomass of sweet potato infected with SPVD increased significantly or extremely significantly. Among the pesticides, BASF virus liquid, 0.1% physcion and Aolike powder for cucumber virus were proved to be the best, as the chlorophyll content and stem length of sweet potato increased significantly. The experiment indicated that the pesticides could reduce the harm of SPVD to sweet potato.

Effects of Growth Period on Quality and Tuber Traits of New Sweetpotato Cultivar Xuzishu 8

Xuzishu 8 is a new cultivated sweetpotato with high anthocyanidin content.The growth period affects its tuber traits and quality.In this study,the changes in sweetpotato shape,number of tubers per plant,rate of big and medium tubers,yield,anthocyanin content and starch content of Xuzishu 8 were investigated under 12 growth periods from 78 to 188 d.The results showed that various traits of Xuzishu 8 were significantly different between different growth periods.The rate of large and medium tubers,the fresh sweetpotato yield,the starch content and the anthocyanin yield increased gradually with the extension of the growth period.The length/width ratio of sweetpotato tubers,the rate of small tubers and the contents of reducing sugar and soluble sugar decreased with the prolongation of the growth period.The correlation analysis showed that the fresh sweetpotato yield was in significant or extremely significant positive correlation with the number of tubers per plant,rate of big and medium tubers,dry matter content,dry yield and starch content.The 148-day growth period treatment exhibited the highest number of tubers per plant,the highest fresh sweetpotato yield and anthocyanin yield reaching 3 927 and 4.25 kg/667 m^2,respectively,as well as the rate of large and medium tubers up to 90%.Therefore,the tubers had good marketability and eating quality.

Breeding and Cultivation Techniques of a New Table Use Purple-fleshed Sweetpotato Cultivar,Xuzishu 2

Xuzishu 2 is a new high-quality table use purple-fleshed sweetpotato cultivar bred from hybrid progenies of AIS35-2 x Xushu 22-5 by Jiangsu Xuzhou Sweetpotato Research Center. In the sweetpotato variety regional trial of Jiangsu Province during 2007 - 2008, average fresh storage root yield was 30 185.3 kg/hm2 ; average dry matter content was 29.26% ; average dry storage root yield was 8 868.7 kg/hm2. In the sweetpotato variety production test of Jiangsu Province, average fresh storage root yield was 30 683.9 kg/hm2 ; average dry storage root yield was 9 399.0 kg/hm2. Multi-location sampling analysis in the regional trial indicated that the anthocyanin content in fresh storage roots was 104.6 μg. Xuzishu 2 was approved by Crop Variety Approval Committee of Jiangsu Province in March 2010, which exhibited high fresh storage root yield, sweet taste, high anthocyanin contem, good commodity, root rot resistance, and was tolerant to moisture and easy to store. Therefore, Xuzishu 2 is a high-quality purple-fleshed sweetpotato variety suitable for consumption and food processing, which should be cultivated in medium- and high-fertility fields with management procedures of suitable high density, early planting and early harvest.

腐植酸尿素对甘薯根系生理特性和产量的影响

腐植酸不仅能促进作物根系的生长,还能与氮结合提高肥料利用率和作物产量。然而,腐植酸尿素(HA-N)对甘薯根系生长和产量影响的研究较少。以“徐薯28号”为试验作物,大田条件下评价了HA-N对甘薯根系形态、活性氧代谢及产量的影响。