抗疫病加工型辣椒细胞质雄性不育恢复系的创制

为加快抗疫病加工型辣椒细胞质雄性不育(cytoplasmic male sterility,CMS)恢复系的创制,该试验以单生、长果自交系481 4 10为母本,以抗疫病的恢复系939 1和1021(1) 1为父本配制杂交组合,采用花药培养技术将抗疫病恢复系的Rf基因和抗疫病基因导入单生、长果自交系中,并利用分子标记辅助选择(molecular marker assisted selection, MAS)技术鉴定DH系(Double Haploid line)的Rf基因以及抗病性,进一步用室内苗期抗性鉴定的方法验证MAS筛选的含Rf DH系对疫病的抗性。结果表明：(1)花药培养的供体亲本(481 4 10×939 1)F₁诱导出22个胚状体,成苗后经倍性鉴定获得11个花培DH系;而由供体亲本［481 4 10×1021(1) 1］F₁获得 9个DH系。(2)分子标记CRF SCAR对花培DH系进行分子标记辅助选择验证结果表明,来自供体(481 4 10×939 1)F₁的DH系中有7个可扩增出870 bp的特异条带,占63.6%;而供体［481 4 10×1021(1) 1］F₁获得的DH系中则有8个能扩增出870 bp的特异条带,占88.9%。(3)分子标记FQ01/RQ01对DH系进行分子标记辅助选择筛选结果发现,来自供体(481 4 10×939 1)F₁的DH系有5个能扩增出717 bp的特异条带,占45.5%;而来自供体［481 4 10×1021(1) 1］F₁的DH系有4个可扩增出717 bp的特异条带,占44.4%。(4)MAS技术初步筛选到7个携带Rf的抗疫病DH系,分别命名为‘渝辣选3 2/3 3/3 5/7 1/7 5/7 6/7 9’;苗期抗性鉴定结果显示,7个DH系中5个DH系抗疫病,2个中抗疫病;农艺性状调查和测交实验表明,‘渝辣选3 2’和‘渝辣选7 1’是单生朝天椒、果实较长,味辣,均为CMS恢复系。该研究创制的2个DH系为利用辣椒CMS三系配套选育抗病新品种奠定了基础。     

Mapping quantitative trait loci associated with southern leaf blight resistance in maize (Zea mays L.)

Southern leaf blight (SLB) caused by the fungus Cochliobolus heterostrophus (Drechs.) Drechs. is a major foliar disease of maize worldwide. Our objectives were to identify quantitative trait loci (QTL) for resistance to SLB and flowering traits in recombinant inbred line (RIL) population derived from the cross of inbred lines LM5 (resistant) and CM140 (susceptible). A set of 207 RILs were phenotyped for resistance to SLB at three time intervals for two consecutive years. Four putative QTL for SLB resistance were detected on chromosomes 3, 8 and 9 that accounted for 54% of the total phenotypic variation. Days to silking and anthesis–silking interval (ASI) QTL were located on chromosomes 6, 7 and 9. A comparison of the obtained results with the published SLB resistance QTL studies suggested that the detected bins 9.03/02 and 8.03/8.02 are the hot spots for SLB resistance whereas novel QTL were identified in bins 3.08 and 8.01/8.04. The linked markers are being utilized for marker‐assisted mobilization of QTL conferring resistance to SLB in elite maize backgrounds. Fine mapping of identified QTL will facilitate identification of candidate genes underlying SLB resistance.     

Xanthomonas hortorum – beyond gardens: Current taxonomy,genomics, and virulence repertoires

TaxonomyBacteria; Phylum Proteobacteria; Class Gammaproteobacteria; Order Lysobacterales (earlier synonym of Xanthomonadales); Family Lysobacteraceae (earlier synonym of Xanthomonadaceae); Genus Xanthomonas; Species X. hortorum; Pathovars: pv. carotae, pv. vitians, pv. hederae, pv. pelargonii, pv. taraxaci, pv. cynarae, and pv. gardneri.Host range Xanthomonas hortorum affects agricultural crops, and horticultural and wild plants. Tomato, carrot, artichoke, lettuce, pelargonium, ivy, and dandelion were originally described as the main natural hosts of the seven separate pathovars. Artificial inoculation experiments also revealed other hosts. The natural and experimental host ranges are expected to be broader than initially assumed. Additionally, several strains, yet to be assigned to a pathovar within X. hortorum, cause diseases on several other plant species such as peony, sweet wormwood, lavender, and oak‐leaf hydrangea.Epidemiology and control X. hortorum pathovars are mainly disseminated by infected seeds (e.g., X. hortorum pvs carotae and vitians) or cuttings (e.g., X. hortorum pv. pelargonii) and can be further dispersed by wind and rain, or mechanically transferred during planting and cultivation. Global trade of plants, seeds, and other propagating material constitutes a major pathway for their introduction and spread into new geographical areas. The propagules of some pathovars (e.g., X. horturum pv. pelargonii) are spread by insect vectors, while those of others can survive in crop residues and soils, and overwinter until the following growing season (e.g., X. hortorum pvs vitians and carotae). Control measures against X. hortorum pathovars are varied and include exclusion strategies (i.e., by using certification programmes and quarantine regulations) to multiple agricultural practices such as the application of phytosanitary products. Copper‐based compounds against X. hortorum are used, but the emergence of copper‐tolerant strains represents a major threat for their effective management. With the current lack of efficient chemical or biological disease management strategies, host resistance appears promising, but is not without challenges. The intrastrain genetic variability within the same pathovar poses a challenge for breeding cultivars with durable resistance.Useful websites https://gd.eppo.int/taxon/XANTGA, https://gd.eppo.int/taxon/XANTCR, https://gd.eppo.int/taxon/XANTPE, https://www.euroxanth.eu, http://www.xanthomonas.org, http://www.xanthomonas.org/dokuwiki     

Occurrence of airborne Cladosporium and Alternaria spores in Southern and Central Poland in 1995–1996

The concentration of airborne spores of Cladosporium and Alternaria has been investigated at five monitoring stations situated in cities from the foot of the Tatra Mountains to central Poland along a south-north transect (Zakopane, Kraków, Ostrowiec witokrzyski, Warszawa, Pozna) i.e. from a height of 900 m to 80 m above sea level. The aerobiological monitoring of fungal spores was performed by means of five Burkard volumetric spore traps.Cladosporium spores were dominant at all the stations. The highest Cladosporium and Alternaria spore concentrations were observed at all the sites in July and August, except at Warszawa in both years and at Pozna in 1995 where the maximum of Cladosporium spores occurred in June and July, and at Ostrowiec witokrzyski in 1995 where the maximum was found in July, August and September.Fungal spore concentrations in Zakopane and Kraków were significantly lower than those in Ostrowiec witokrzyski, Warszawa and Pozna and periods of abundant Cladosporium spore occurrence were different in these two groups of monitoring stations.     

Biotransformation of solidagenone by Alternaria alternata, Aspergillus niger and Curvularia lunata cultures

The microbiological oxidation of the diterpene solidagenone by Curvularia lunata afforded 3-hydroxysolidagenone and 3-oxosolidagenone as well as the fungal compounds radicinol and isoradicinol. Fermentation of solidagenone with Aspergillus niger afforded 3-hydroxy- and 19-hydroxysolidagenone while with Alternaria alternata yielded 3-oxosolidagenone. The structure of 3-oxosolidagenone is presented for the first time.     

Use of asymmetric somatic hybridization for transfer of the bacterial blight resistance trait from Oryza meyeriana L. to O. sativa L. ssp. japonica

Bacterial blight is one of the major diseases affecting rice productivity. To improve the resistance of cultivated rice to bacterial blight, we introduced a bacterial blight resistance trait from Oryza meyeriana, a wild rice species, into an elite japonica rice cultivar (Dalixiang) using asymmetric somatic hybridization. One hundred and thirty-two independent lines were regenerated. The hybrid plants possessed several morphological features of the donor species, O. meyeriana. Random amplified polymorphic DNA analysis revealed that hybrid plants exhibited banding patterns derived from their parental genotypes. For the majority of the hybrids, resistance to bacterial blight pathogens was intermediate to that observed for O. meyeriana and O. sativa (cv. Dalixiang). Four of the hybrid lines exhibited a high bacterial blight resistance, but it was less than that observed for O. meyeriana. These results demonstrate that O. meyeriana can be used as a good genetic source for improving bacterial blight resistance in commercial rice cultivars through asymmetric somatic hybridization.Abbreviations 2,4-D: 2,4-Dichlorophenoxyacetic acid - IOA: Iodoacetamide - NAA: -Naphthaleneacetic acid - PEG: Polyethylene glycol Communicated by P. Lakshmanan     

A unigene catalogue of 5700 expressed genes in cassava

Two economically important characters, starch content and cassava bacterial blight resistance, were targeted to generate a large collection of cassava ESTs. Two libraries were constructed from cassava root tissues of varieties with high and low starch contents. Other libraries were constructed from plant tissues challenged by the pathogen Xanthomonas axonopodis pv.manihotis. We report here the single pass sequencing of 11 954 cDNA clones from the 5’ ends, including 111 from the 3’ ends. Cluster analysis permitted the identification of a unigene set of 5700 sequences. Sequence analyses permitted the assignment of a putative functional category for 37% of sequences whereas ~ 16% sequences did not show any significant similarity with other proteins present in the database and therefore can be considered as cassava specific genes. A group of genes belonging to a large multigene family was identified. We characterize a set of genes detected only in infected libraries putatively involved in the defense response to pathogen infection. By comparing two libraries obtained from cultivars contrasting in their starch content a group of genes associated to starch biosynthesis and differentially expressed was identified. This is the first large cassava EST resource developed today and publicly available thus making a significant contribution to genomic knowledge of cassava.     

Effect of static magnetic field on growth and sporulation of some plant pathogenic fungi

Growth and sporulation of phytopathogenic microscopic fungi were studied under a static magnetic field. The applied flux densities were 0.1, 0.5, and 1 mT. The magnetic field decreased the growth of colonies by 10% using this flux density region. At 0.1 mT flux density, the deviations are significant, P =.001, while in other cases the deviations generally are not significant. At the same time, the number of the developed conidia of Alternaria alternata and Curvularia inaequalis increased by 68-133%, but the number of Fusarium oxysporum conidia decreased by 79-83%. The deviations are generally significant at the P =.05 level.