Genetics of Fertility Restoration in Cytoplasmic Male Sterile Pepper

Pepper hybrid seeds production using male sterility could lower cost by reducing time and labour, and increase the genetic purity of the F1 seeds. To investigate the genetics of fertility restoration of the Peterson cytoplasmic sterility in pepper, a doubled haploid population of 115 pepper lines obtained from anther culture of the F1 hybrid between Yolo Wonder （sterility maintainer line） and Perennial （fertility restorer line） and the parental lines were test-crossed by 77013A （a strict cytoplasmic-genic male sterile line）. The fertility of the test-crossed lines was assessed in greenhouse and open field with the following three criteria： pollen index （PI, visual estimation of pollen amount per flower）, pollen number （PN, pollen counting under microscope）, and seed number （SN, the number of seeds per fruit in open pollination）. Correlations between the each couple of criteria within, as well as between the cultivation methods ranged from 0.55 to 0.84. Analysis of variance showed that the genotype （DH line） and environment were the significant sources of variation of the fertility. Narrow sense of heritance of fertility restoration ranged from 0.38 to 0.92, depending on the criteria and environment. The distribution of the progeny was continuous between the parental genotypes indicating the quantitative inheritance of fertility restoration. Inferred from segregation according to Snape et al.（1984）, the number of segregating genes was estimated to be that three to four genetic factors were involved in pollen traits （PI and PN） and five to eight genetic factors in seed production （SN）. The heredity analysis of the CMS will be helpful for understanding of the genetic mechanism of the fertility restoration and the exploitation of the CMS in hybrid seed production.

Genetic diversity of pepper(Capsicum spp.) germplasm resources in China reflects selection for cultivar types and spatial distribution

Pepper（Capsicum spp.） is an important vegetable crop in the world. Now the pepper in China contributes one-third of the world＇s peppers production. Genetic diversity of the pepper germplasm of China is expected interesting to know. To explore the structure of genetic diversity in Chinese pepper germplasm resources and possible relationship with cultivar types or geographic origin, we sampled and compared 372 Gen Bank pepper accessions（local cultivars and landraces） from 31 provinces, autonomous regions and municipalities of China and 31 additional accessions from other countries. These accessions were genotyped using 28 simple sequence repeat（SSR） markers spanning the entire pepper genome. We then investigated the genetic structure of the sampled collection using model-based analysis in STRUCTURE v2.3.4 and examined genetic relationships by the unweighted pair-group method of mathematical averages（UPGMA） in MEGA. In addition to geographic origin, we evaluated eight plant and fruit traits. In total, 363 alleles were amplified using the 28 SSR primers. Gene diversity, polymorphism information content and heterozygosity of the 28 SSR loci were estimated as 0.09–0.92, 0.08–0.92 and 0.01–0.34, respectively. The UPGMA cluster analysis clearly distinguished Capsicum annuum L. from other cultivated pepper species. Population structure analysis of the 368 C. annuum accessions uncovered three genetic groups which also corresponded to distinct cultivar types with respect to the plant and fruit descriptors. The genetic structure was also related to the geographic origin of the landraces. Overall results indicate that genetic diversity of Chinese pepper landraces were structured by migration of genotypes followed by human selection for cultivar types in agreement with consumption modes and adaptation to the highly diversified agro-climatic conditions.

Accumulation and Distribution Dynamics of Soluble Carbohydrate in Helianthus tuberosus under Drought Stress

With Qingyu 1 and Qingyu 2 as test materials, variation of soluble carbohydrate content in different parts were studied under two types of artificially simulated drought stress （polyethylene glycd PEG-6000 stress and water-controlling stress）. The results showed that under the stress of PEG, soluble carbohydrate content in leaves of Qingyu 1 and Qingyu 2 increased with the prolonging time of stress; soluble carbohydrate content in stems of Qingyu 1 did not show regular changes with the prolonging time of stress, while 30% PEG stress received the best effect on Qingyu 2 after 24 h; soluble carbohydrate content in roots of Qingyu 1 and Qingyu 2 increased with the prolonging time of stress. Under different intensities of water-controUing stress, soluble carbohydrate content in leaves of Qingyu 1 first increased then decreased, while that in leaves of Qingyu 2 increased; soluble carbohydrate content in stems of Qingyu 1 and Qingyu 2 increased with the pro- longing time of water-controlling stress; soluble carbohydrate content in roots of Qingyu 1 decreased with the prolonging time of water-contmlling stress, while that in roots of Qingyu 2 differed slightly.

Inhibitory Effect of Extracts from Helianthus tuberosus Leaves against Phytophthora capsici and Pot Verification Test

By growth rate method, the inhibitory effects of five solvent extracts from Helianthus tuberosus leaves against Phytophthora capsici were studied in the test. The results showed that different solvent extracts all had inhibitory effect against P. capsici, while 12.5 mg/mL of extracts from H. tuberosus leaves with petroleum ether and ethyl acetate as solvents had the highest inhibitory effect against P. capsici, reaching 100%. In case of various solvent extracts with different concentration gradients, ethyl acetate extract had the most significant inhibitory effect; when the concentration was 5 mg/mL, the inhibitory effect of ethyl acetate extract had reached 100% ; when the concentration reduced to 2.5 mg/mL, the inhibitory effect was still （27.91 ±2. 076） %, significantly higher than that of other solvent extracts at the same concentration. The 50 times dilution of ethyl acetate extract from H. tuberosus leaves was selected for pot test against pepper blight. , and the results showed that its control effect against pepper blight reached 100.00%, superior than that of chemical agent 25% metalaxyl WP 400 times dilution.

Study on Accumulation and Dynamic Changes of Three Carbohydrates in Jerusalem Artichoke in Natural Habitats

Two varieties of Jerusalem artichoke (early maturing variety Qingyu No.1 and middle maturing variety Qingyu No.2),which were bred independently by Research and Development Center of Jerusalem Artichoke,Qinghai Academy of Agriculture and Forestry,were used as materials,and the content and dynamic changes of three kinds of carbohydrates (sucrose,glucose and fructose) in various organs of Jerusalem artichoke in different periods in two natural habitats (water plain and low hill dry land) were studied.The results showed that the content of the three kinds of carbohydrates in Qingyu No.1 and Qingyu No.2 in the water plain and low hill dry land was relatively high in late June and late August.The total content of the three carbohydrates in Qingyu No.1 peaked earlier than that of Qingyu No.2.The total content of the three carbohydrates in the water plain peaked earlier than that of the low hill dry land.In the whole growth period,the total content of the three carbohydrates in the stems and roots of Jerusalem artichoke was higher than that of the leaves.In the leaves,fructose accumulation was relatively obvious in the whole growth period,and the content was high,followed by glucose.In the stems and roots,fructose content was high,followed by sucrose.In the tubers,glucose accumulation was obvious,and sucrose content was lower than glucose and fructose content.When the tubers were harvested,fructose content was high.

Analysis of SSRs Information in Capsicum spp. from EST Database

SSR markers are useful in pepper linkage mapping and gene location. 446 SSR markers have been reported, but they are insufficient. It is costly to develop SSR markers from DNA library, whereas it seems much easy to find in EST sequences in the GenBank of pepper through internet. In this study, attempts have been made to develop SSR markers in the EST sequences by using bioinformatics. EST sequences were trimmed by ‘est-trimmer.pl’ software, while 116 915 EST sequences were obtained without poly ‘A’ or poly ‘T’, ranged between 100 and 700 bp. Using ‘e-PCR’ and ‘del.pl’ softwares, SSR sequences were identified. 2 508 microsatellite loci （larger than 20 repeats） were established and 755 SSR primers were designed using SSR finder software and Primer 3 software. There were 498 （0.43%） mono-, 1 026 （0.89%） di-, 518 （0.45%） tri-, 245 （0.21%） tetra-, 114 （0.10%） penta-, and 107 （0.09%） hexa-nucleotide SSRs. The estimated frequency of SSRs was approximately 1/25.12 kb. According to the distribution of SSRs in pepper, the mean length of pepper SSRs was 22.68 bp and the adenine rich repeats such as A/T, AG, AT, AAG, AAAT, and AAAC were predominant in each type of SSRs （mono-, di-, tri-, tetra-, penta-, and hexa-）, whereas the C/G, CG, CCG repeats were less abundant. 210 primers were tested in 8 pepper cultivars and the PCR result revealed the existence of polymorphism among 127 （60.48%） SSR primers within 8 pepper cultivars. It is confirmed that pepper EST database could be efficiently exploited for availability of SSR markers.

A predicted NEDD8 conjugating enzyme gene identified as a Capsicum candidate Rf gene using bulk segregant RNA sequencing

Cytoplasmic male sterility(CMS)is an important tool for producing F1 hybrids,which can exhibit heterosis.The companion system,restorer-of-fertility(Rf),is poorly understood at the molecular level and would be valuable in producing restorer lines for hybrid seed production.The identity of the Rf gene in Capsicum(pepper)is currently unclear.In this study,using bulked segregant RNA sequencing(BSR-seq),a strong candidate Rf gene,Capana06g002866,which is annotated as a NEDD8 conjugating enzyme E2,was identified.Capana06g002866 has an ORF of 555 bp in length encoding 184 amino acids;it can be cloned from F1 plants from the hybridization of the CMS line 8A and restorer line R1 but is not found in CMS line 8A.With qRT-PCR validation,Capana06g002866 was found to be upregulated in restorer accessions compared to sterile accessions.The relative expression in flower buds increased with the developmental stage in F1 plants,while the expression was very low in all flower bud stages of the CMS lines.These results provide new insights into the Rf gene in pepper and will be useful for other crops utilizing the CMS system.

An Analysis on Leaf Traits of 22 Helianthus tuberosus Germplasm Resources Introduced from Abroad

Atomic absorption spectrophotometry,sulfuric acid and potassium dichromate oxidation method and ultraviolet spectrophotometry,were used to determine mineral elements,fiber,the content of chlorogenic acid and flavones in leaves of 24 Helianthus tuberosus Linn.resources,and the characteristics of the leaf introduced from abroad were evaluated.The results showed that the highest water content of 22 species was F12(27.58%),and the lowest was F16(19.02%).The difference in mean water content between the species from Denmark and France was small,but it was lower than that of Qingyu 3 and Qingyu 4.There were 3 orbicular leaves,1 long oval-shaped leaf and 18 oval leaves.The highest K content in the leaves was F19(30.62 mg/g),which was 2.5 times than Qingyu 3.The highest Mg content was D8(14.17 mg/g).The Fe content hadlittledifference,ranging from 0.09 mg/g to 0.19 mg/g.The highest Ca content was D8(26.87 mg/g).The highest level of chlorogenic acid and flavones was F7,2.55%and 1.24 g/100 g respectively.The highest fiber content was F9(16.7%),and the lowest was F19(7.36%).Through the analysis of the main component and the clustering analysis,when the genetic distance was 0.65,the 24 resources can be divided into three major categories.The first category of leaves were mainly oval and orbicular;the second category of leaves were long oval-shaped;the third category of leaves were oval.There was a difference between the various indexes in the leaf of different kinds of H.tuberosus Linn.resources.Finally,F19,D8,F9,F7,D14 and D11,6 specific species(F19,D8,F9,F7,D14 and D11)were screened out for further studies in the future.