Screening of Tobacco Genotypes for <em>Phytophthora nicotianae</em> Resistance

Black shank, caused by the oomycetes Phytophthora nicotianae, is destructive to tobacco, and this pathogen is highly pathogenic to many solanaceous crops. ...

Chinese Academy of Agricultural Sciences

Reproductive period (RP) is an important trait of soybean [Glycine max (L.) Merr.] It is closely related to yield, quality and tolerances to environmental stresses. To investigate the inheritance and photoperiod response of RP in soybean, the F(1), F(2), and F(2:3) populations derived from nine crosses were developed. The inheritance of RP was analyzed through the joint segregation analysis. It was shown that the RP was controlled by one major gene plus polygenes. 181 recombinant inbred lines (RILs) generated from the cross of Xuyong Hongdou × Baohexuan 3 were further used for QTL mapping of RP under normal conditions across 3 environments, using 127 SSR markers. Four QTLs, designated qRP-c-1, qRP-g-1, qRP-m-1 and qRP-m-2, were mapped on C1, G and M linkage groups, respectively. The QTL qRP-c-1 on the linkage group C1 showed stable effect across environments and explained 25.6, 27.5 and 21.4% of the phenotypic variance in Nanjing 2002, Beijing 2003 and Beijing 2004, respectively. Under photoperiod-controlled conditions, qRP-c-1, and two different QTLs designated qRP-l-1 and qRP-o-1, respectively, were mapped on the linkage groups L and O. qRP-o-1 was detected under SD condition and can explained 10.70% of the phenotypic variance. qRP-c-1 and qRP-l-1 were detected under LD condition and for photoperiod sensitivity. The two major-effect QTLs can explain 19.03 and 19.00% of the phenotypic variance, respectively, under LD condition and 16.25 and 14.12%, respectively, for photoperiod sensitivity. Comparative mapping suggested that the two major-effect QTLs, qRP-c-1 and qRP-l-1, might associate with E8 or GmCRY1a and the maturity gene E3 or GmPhyA3, respectively. These results could facilitate our understanding of the inheritance of RP and provide information on marker-assisted breeding for high yield and wide adaptation in soybean.

Genetic analysis and QTL detection of reproductive period and post-flowering photoperiod responses in soybean.

Effect of genetic background on detection of quantitative trait locus (QTL) governing salinity tolerance (ST) was studied using two sets of reciprocal introgression lines (ILs) derived from a cross between a moderately salinity tolerant japonica variety, Xiushui09 from China, and a drought tolerant but salinity susceptible indica breeding line, IR2061-520-6-9 from the Philippines. Salt toxicity symptoms (SST) on leaves, days to seedling survival (DSS), and sodium and potassium uptake by shoots were measured under salinity stress of 140 mmol/L of NaCl. A total of 47 QTLs, including 26 main-effect QTLs (M-QTLs) and 21 epistatic QTLs (E-QTLs), were identified from the two sets of reciprocal ILs. Among the 26 M-QTLs, only four (15.4%) were shared in the reciprocal backgrounds while no shared E-QTLs were detected, indicating that ST QTLs, especially E-QTLs, were very specific to the genetic background. Further, 78.6% of the M-QTLs for SST and DSS identified in the reciprocal ILs were also detected in the recombinant inbred lines (RILs) from the same cross, which clearly brings out the background effect on ST QTL detection and its utilization in ST breeding. The detection of ILs with various levels of pyramiding of nonallelic M-QTL alleles for ST from Xiushui09 into IR2061-520-6-9 allowed us to further improve the ST in rice.

Identification of salt-tolerant QTLs with strong genetic background effect using two sets of reciprocal introgression lines in rice.

Cucumber mosaic virus (CMV) is among the most important plant virus infections, inducing a variety of disease symptoms. However, the molecular mechanisms underlying plant responses to CMV infection remain poorly understood. In this study, we performed RNA sequencing analysis of tolerant (Taiyan8) and susceptible (NC82) tobacco cultivars on CMV-infected plants, using mock-inoculated plants as a control. The propagation of CMV in inoculated leaves did not show obvious difference between two cultivars, whereas virus accumulation in systemic leaves of Taiyan8 was smaller than those of NC82 at the same time point. We observed 765 and 1,011 differentially expressed genes (DEGs) in Taiyan8 and NC82, respectively, in CMV-inoculated leaves. DEGs related to reactive oxygen species, salicylic acid signal transduction, and plant-pathogen interaction were upregulated or downregulated in Taiyan8, which indicates that defense response pathways to CMV were activated in the tolerant cultivar. In addition, we identified several DEGs related to disease defense and stress resistance showing opposing expression patterns in the two cultivars. Our comparative transcriptome analysis will improve our understanding of the mechanisms of CMV tolerance in plants, and will be of great importance in the molecular breeding of CMV- tolerant genotypes.

Transcriptome analysis of two cultivars of tobacco in response to Cucumber mosaic virus infection.

At present, the distinctness, uniformity, and stability (DUS) testing of flue-cured tobacco (Nicotiana tabacum L.) depends on field morphological identification, which is problematic in that it is labor intensive, time-consuming, and susceptible to environmental impacts. In order to improve the efficiency and accuracy of tobacco DUS testing, the development of a molecular marker-based method for genetic diversity identification is urgently needed.

Genetic diversity and fingerprinting of 33 standard flue-cured tobacco varieties for use in distinctness, uniformity, and stability testing.

Phytophthora nicotianae is highly pathogenic to Solanaceous crops and is a major problem in tobacco production. The tobacco cultivar Beihart1000-1 (BH) is resistant, whereas the Xiaohuangjin 1025 (XHJ) cultivar is susceptible to infection. Here, BH and XHJ were used as models to identify resistant and susceptible genes using RNA sequencing (RNA-seq). Roots were sampled at 0, 6, 12, 24, and 60 h post infection. In total, 23,753 and 25,187 differentially expressed genes (DEGs) were identified in BH and XHJ, respectively. By mapping upregulated DEGs to the KEGG database, changes of the rich factor of "plant pathogen interaction pathway" were corresponded to the infection process. Of all the DEGs in this pathway, 38 were specifically regulated in BH. These genes included 11 disease-resistance proteins, 3 pathogenesis-related proteins, 4 RLP/RLKs, 2 CNGCs, 7 calcium-dependent protein kinases, 4 calcium-binding proteins, 1 mitogen-activated protein kinase kinase, 1 protein EDS1L, 2 WRKY transcription factors, 1 mannosyltransferase, and 1 calmodulin-like protein. By combining the analysis of reported susceptible (S) gene homologs and DEGs in XHJ, 9 S gene homologs were identified, which included 1 calmodulin-binding transcription activator, 1 cyclic nucleotide-gated ion channel, 1 protein trichome birefringence-like protein, 1 plant UBX domain-containing protein, 1 ADP-ribosylation factor GTPase-activating protein, 2 callose synthases, and 2 cellulose synthase A catalytic subunits. qRT-PCR was used to validate the RNA-seq data. The comprehensive transcriptome dataset described here, including candidate resistant and susceptible genes, will provide a valuable resource for breeding tobacco plants resistant to P. nicotianae infections.

Lirui Cheng

Key Laboratory of Tobacco Genetic Improvement and Biotechnology,
Tobacco Research Institute,
Key Laboratory of Tobacco Genetic Improvement and Biotechnology, Tobacco Research Institute

Chinese Academy of Agricultural Sciences

Screening of Tobacco Genotypes for Phytophthora nicotianae Resistance

Lirui Cheng

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Key Laboratory of Tobacco Genetic Improvement and Biotechnology,Tobacco Research Institute,Key Laboratory of Tobacco Genetic Improvement and Biotechnology, Tobacco Research Institute

Chinese Academy of Agricultural Sciences

Screening of Tobacco Genotypes for Phytophthora nicotianae Resistance

Key Laboratory of Tobacco Genetic Improvement and Biotechnology,
Tobacco Research Institute,
Key Laboratory of Tobacco Genetic Improvement and Biotechnology, Tobacco Research Institute