Evaluation of Chinese rice varieties resistant to the root-knot nematode Meloidogyne graminicola

The root-knot nematode Meloidogyne graminicola, which is distributed worldwide, is considered a major constraint on rice production in Asia. The present study used the root gall index and number of nematodes inside the roots to evaluate resistance/susceptibility to M. graminicola in different subpopulations of Oryza sativa （aus, hybrid aus, indica, hybrid indica, temperate japonica, tropical japonica）. Nematode development in highly resistant varieties was also evaluated. Analyses of randomly selected 35 varieties showed the number of M. graminicola nematodes inside the roots correlated very strongly （r=0.87, P≤0.05） with the nematode gall index, and the results from pot and field experiments revealed similar rankings of the varieties for resistance/susceptibility. Among the 136 tested varieties, temperate japonica displayed the highest gall index, followed by tropical japonica, indica, hybrid indica, aus, and hybrid aus. Zhonghua 11 （aus）, Shenliangyou 1 （hybrid aus） and Cliangyou 4418 （hybrid indica） were highly resistant to M. graminicola under both pot and field conditions. Further examination of nematode development suggested that compared to susceptible rice, M. graminicola penetrated less often into highly resistant varieties and more frequently failed to develop into females. The promising varieties found in the present research might be useful for the breeding of hybrid rice in China and for the further development of practical nematode management measures.

Evaluation of the early defoliation trait and identification of resistance genes through a comprehensive transcriptome analysis in pears

Early defoliation,which usually occurs during summer in pear trees,is gradually becoming a major problem that poses a serious threat to the pear industry in southern China.However,there is no system for evaluating the responses of different cultivars to early defoliation,and our knowledge of the potential molecular regulation of the genes underlying this phenomenon is still limited.In this study,we conducted field investigations of 155 pear accessions to assess their resistance or susceptibility to early defoliation.A total of 126 accessions were found to be susceptible to early defoliation,and only 29 accessions were resistant.Among them,19 resistant accessions belong to the sand pear species(Pyrus pyrifolia).To identify the resistance genes related to early defoliation,the healthy and diseased samples of two sand pear accessions,namely,the resistant early defoliation accession‘Whasan’and the susceptible early defoliation accession‘Cuiguan’,were used to perform RNA sequencing.Compared with‘Cuiguan’,a total of 444 genes were uniquely differentially expressed in‘Whasan’.Combined with GO and KEGG enrichment analyses,we found that early defoliation was closely related to the stress response.Furthermore,a weighted gene co-expression network analysis revealed a high correlation of WRKY and ethylene responsive factor(ERF)transcription factors with early defoliation resistance.This study provides useful resistant germplasm resources and new insights into potentially essential genes that respond to early defoliation in pears,which may facilitate a better understanding of the resistance mechanism and molecular breeding of resistant pear cultivars.

Evaluation of Rice Germplasm for Resistance to the Small Brown Planthopper (Laodelphax striatellus) and Analysis of Resistance Mechanism

One hundred and thirty-eight rice accessions were screened for resistance to the small brown planthopper （SBPH） （Laodelphax striatellus Fallen） by the modified seedbox screening test. Twenty-five rice accessions with different levels of resistance to SBPH were detected, accounting for 18.1% of the total accessions, which included 2 highly resistant, 9 resistant and 14 moderately resistant varieties. Compared with indica rice, japonica rice was more susceptible to SBPH. Antixenosis test, antibiosis test and correlation analysis were performed to elucidate the resistance mechanism. The resistant check Rathu Heenati （RHT）, highly resistant varieties Mudgo and Kasalath, and resistant variety IR36 expressed strong antixenosis and antibiosis against SBPH, indicating the close relationship between resistance level and these two resistance mechanisms in the four rice varieties. Antibiosis was the dominant resistance pattern in the resistant varieties Daorenqiao and Yangmaogu due to their high antibiosis but low antixenosis. Dular, ASD7 and Milyang 23 had relatively strong antixenosis and antibiosis, indicating the two resistance mechanisms were significant in these three varieties. The resistant DV85 expressed relatively high level of antixenosis but low antibiosis, whereas Zhaiyeqing 8 and Guiyigu conferred only moderate antibiosis and antixenosis to SBPH, suggesting tolerance in these three varieties. Antibiosis and antixenosis governed the resistance to SBPH in the moderately resistant accession 9311. Antixenosis was the main resistance type in V20A. Tolerance was considered to be an important resistance mechanism in Minghui 63 and Yangjing 9538 due to their poor antibiosis and antixenosis resistance. The above accessions with strong antibiosis or antixenosis were the ideal materials for the resistance breeding.

Molecular Screening and Resistance Evaluation of American Wheat Cultivars to Chinese Stripe Rust Races

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the major diseases of wheat in China. In order to asses the resistance levels and existing Yr genes among 59 wheat cultivars （lines） from the Pacific Northwest （PNW） of the United States, to provide resistance resources for genetic improvement of wheat stripe rust resistance in China, 59 wheat cultivars （lines） from PNW of the United States were infected by 3 mixed races of predominant Chinese stripe rust races CRY31, CRY32, and CRY33 to evaluate their resistance at seedling and adult plant stages, and screened with molecular markers tightly linked to currently effective all-stage resistance genes YrlO, Yrl5 and adult plant resistance genes Yrl8, Yr39. Of 59 American cultivars （lines）, five cultivars （lines）, Expresso, 02W50076, ACS52610, WA008012, and WA00801833, had all-stage resistance, showing resistance to mixed races of CRY31, CRY32, and CRY33 at both seedling and adult plant stages. 33 cultivars （lines） had adult plant resistance, only showing resistance to stripe rust at adult stage. Based on the molecular screening, none of the 59 PNW cultivars （lines） had the polymorphic bands of linked markers to YrlO. There were 12, 33 and 29 cultivars （lines） which bad polymorphic bands of linked markers to Yr15, Yr18 and Yr39, accounting for 20, 55 and 49% of the 59 PNW cultivars （lines）, respectively. All these results suggested that Yr15, Yr18 and Yr39 were widespread among PNW cultivars （cultivars） and could be utilized in Chinese wheat stripe rust resistance breeding.

Performances and Germplasm Evaluation of Quantitative Resistance to Soybean Mosaic Virus in Soybeans

A sample composed of 96 soybean accessions was evaluated for their diseased rate (I),diseased rank (S), latent period (LP) and rate of disease development (R) in order tostudy the quantitative resistance to soybean mosaic virus (SMV) in soybeans. The resultsshowed that the performances of the above four resistance components were significantlydifferent among accessions and that some of the accessions, such as Zhongzihuangdou,Peixian Tianedan, Youbian30 could be infected by four SMV strains, Sa, SC8, N1 and N3,but their I, S, and R were lower and LP longer than most other accessions. These resultsdemonstrated the existence of quantitative resistance to SMV in soybeans. It was foundthat some soybean accessions, such as AGS19 and Lishui Zhongzihuangdou, previouslyidentified as resistant to SMV infection, performed some infection but resistant toexpansion in the present study. In addition, the resistance in Pixian Chadou and HuaiyinQiuheidou might be either qualitative or quantitative. Furthermore, the present studyalso indicated that the resistance spectrum and durability of accessions with quantitativeresistance might be wider and longer than those with qualitative resistance.

Influence of different inoculation methods on the evaluation of the resistance to rice sheath blight(Rhizoctonia solani Kuhn)

To establish a standard system for geneticstudies on sheath blight resistance, a field testwas conducted at the experimental farm ofYangzhou University to compare several pro-cedures for inoculating rice plants with R.solani Kuhn (RH9). The varieties used wereJasmine 85, Teqing (resistant or moderatelyresistant), and Lemont (susceptible). They

Evaluation on Diseases Resistance of Cotton Material and Its Utilization

Fusarium wilt and Verticillium wilt are important worldwide fungal diseases on cotton that cause damage to yield and quality.The pathogens survive in soil as microsclerotia for many years,and

Evaluation and screening for resistance of some varieties(lines)to major diseases and insect pests of rice

During 1984-1988,2,231 varieties(lines)from International Rice Testing Program(IRTP)were evaluated and screened for resistance to riceblast(Bl),bacterial blight(BB),sheath blight

Evaluation of Resistance of Different Kiwifruit Varieties (Lines) to Canker Disease and Brown Spot Disease

Kiwifruit canker and brown spot are significant diseases affecting kiwis,caused by Pseudomonas syringae patho-genic variations(Pseudomonas syringae pv.Actinidiae(Psa))and Corynesporapolytica(Corynespora cassiicola).At present,the research on canker disease and brown spot disease mainly focuses on the isolation and identification of pathogenic bacteria,drug control,resistance gene mining and functional verification.Practice has proved that breeding disease resistant varieties are an effective method to control canker disease and brown spot disease.However,most existing cultivars lack genes for canker and brown spot resistance.Wild kiwifruit resources in nat-ure exhibit extensive genetic diversity due to prolonged natural selection,containing numerous resistance genes.But,due to insufficient understanding of the resistance of most kiwifruit varieties(lines)to canker disease and brown spot disease,some high-quality resources have not been fully utilized.The incidence of canker and brown spot of 18 kiwifruit cultivars(lines)was measured by inoculating isolated branches and leaves,and their resistance to canker and brown spot was analyzed according to the length,disease index,mean diameter,and systematic clustering.The results were as follows:Among 18 different kiwifruit varieties(lines)for canker disease,there were two highly resistant materials,eight disease-resistant materials,four disease-susceptible materials,and two highly susceptible materials.Moreover,regarding brown spot disease,there were one highly resistant material,five dis-ease-resistant materials,four susceptible materials,and three highly susceptible materials.Furthermore,four resources were resistant to both diseases.The outcomes provided a theoretical basis for breeding kiwifruit against canker and brown spot.

Research progress on plant tolerance to soil salinity and alkalinity in sorghum

Sorghum is an important source of food, feed and raw material for brewing, and is expected to be a promising bioenergy crop. Sorghum is well known for its strong resistance to abiotic stress and wide adaptability, and salt tolerance is one of its main characteristics. Increasing sorghum planting acreage on saline-alkalien land is one way to effectively use this kind of marginal soil. In this paper, domestic and overseas research on plant tolerance to soil salinity and alkalinity in sorghum, including salt-tolerant genetics and breeding, physiology, cultivation, and identification of tolerant germplasms, are reviewed. Suggestions for further studies on salinity and alkalinity tolerance in sorghum are given, and the prospects for sorghum production in saline-alkalien land are discussed.

Physiological Changes and Cold Tolerance of Three Camphor Species During Natural Winter Temperature Fluctuations

The dynamic changes in the malondialdehyde（MDA）, superoxide dismutase（SOD）, soluble sugar, proline, and soluble protein contents, as well as the relative electrolyte conductivity and the corresponding cold resistance, of Cinnamomum bodinieri Level., C. camphora L., and C. caudiferum Kisterm were investigated during the winter months of October 2009 to April 2010. During the short period of temperature decline that lasted until mid-December, the changes in the relative electrolyte conductivity and MDA content with temperature were insignificant. In January, SOD activity continued to increase and then peaked as a result of rapid increases in soluble sugar, proline, soluble protein, as well as the inhibition of the relative electrolyte conductivity and decrease in MDA content. These physiological changes protected the camphor trees from cold damage during winter. From February to March, SOD activity and the soluble protein and proline contents increased with the increase in temperature. However, the relative electrolyte conductivity and MDA content decreased, indicating that the cell membrane damaged by low temperature was gradually being repaired. The cold dip in April led to slight increases in the relative electrolyte conductivity and MDA content. Using a fuzzy mathematics method, the cold resistance adaptability of the camphor trees was divided into three periods namely, the enhancement setting stage, the vigorous stage, and the reducing stage. The cold tolerance abilities were ranked as the following order： C. bodinieri Level〉C. camphora L.〉C. caudiferum Kisterm.

Resistance of barley varieties to Heterodera avenae in the Qinghai–Tibet Plateau,China

The cereal cyst nematode,Heterodera avenae,is one of the most economically important pathogens impacting the worldwide production of cereals and is widely distributed in more than 16 regions in China.The present study used the numbers of nematodes inside the plant roots to evaluate the resistance/susceptibility of different subpopulations of barley Hordeum vulgare(QH2R,QH6R and TB2R)to H.avenae under field and pot conditions.Nematode development in two highly resistant varieties was also evaluated by in vivo experiment and microscopic observation.Analyses of 186selected varieties showed the numbers of susceptible varieties identified with the number of females/cysts per plant(NFP)method were significantly higher than those identified with the Pf/Pi ratio(PPR)method,which indicated that the NFP method rather than the PPR method is more reliable to evaluate the resistance of barley.The field and pot experiment results indicated that the QH2R subpopulation had lower females/cysts numbers than QH6R and TB2R subpopulations,and eight HR varieties(Sunong 7617,Sunong 7635,Dongyuan 87-14,Rudong 14-46,Rudong 87-57,Rudong 87-8-45,Rudong 88-14-2,and Rudong 88-67-1)were identified in QH2R,with the NFP numbers below 4.2.Further microscopic observation of nematode development suggested that H.avenae often penetrated less into highly resistant varieties(Sunong 7635 and Dongyuan 87-14)and more frequently failed to develop into females than the susceptible barleys.The promising resistant varieties identified in the present research might be helpful for breeders to develop CCN-resistant cultivars and control H.avenae populations effectively at low costs.

Jellyfish Green Fluorescent Protein(GFP) as a Reporter for Fusarium gramminearum Development on Wheat

The plasmid pGPDGFP under the control ofpgpdA promotor was used together with vector pAN7-1 containing the hygromycin resistance cassette to co-transform protoplasts of HG1, Fusarium graminearum from Hubei Province, China. Twelve out of 14 hygromycin-resistant transformants showed green signal under the UV light and contained one or several copies ofgfp, as indicated by Southern analysis of genomic DNA digested with different restriction enzymes and hybridized to the gfp probe. A single gfp copy transformant （HG1C5） was selected for further evaluation of 80 Chinese wheat cultivars or advanced lines. The results showed different resistance type to F. graminearum were observed. GFP signals observed in the rachis and adjacent spikes of 70 Chinese wheat lines such as Chuanchongzu 104 indicated both type I （host resistance to the initial infection by the fungus） and type II （resistance to the spread of FHB symptoms within an infected spike） were not observed. While other 10 lines showed type II resistance to F. graminearum with GFP signals only in inoculated spikelets. Development of the mycelium can be intuitively observed and the resistance of wheat to F. graminearum can be identified at 7 days post inoculation （dpi） in this way. The results showed no differences were evaluated between the transformed HG1C5 and the non-transgene artificial inoculation by SAS paired chi-square test and McNernar＇s test （P=-0.0625）.