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Karnal bunt (KB) of wheat, caused by Tilletia indica, is one of the greatest challenges to grain industry, not because of yield loss, but quarantine regulations that restrict international movement and trade of affected stocks. Genetic resistance is the best way to manage this disease. Although several different sources of resistance have been identified to date, very few of those have been subjected to genetic analyses. Understanding the genetics of resistance, characterization and mapping of new resistance loci can help in development of improved germplasm. The objective of this study was to identify and characterize resistance loci (QTL) in two independent recombinant inbred lines (RILs) populations utilizing different wheat lines as resistance donors. Elite CIMMYT wheat lines Blouk#1 and Huirivis#1 were used as susceptible female parents and WHEAR/KUKUNA/3/C80.1/3∗BATAVIA//2∗WBLL1 (WKCBW) and Mutus as moderately resistant male parents in Pop1 and Pop2 populations, respectively. Populations were evaluated for KB resistance in 2015–16 and 2016–17 cropping seasons at two seeding dates (total four environments) in Cd. Obregon, Mexico. Two stable QTL from each population were identified in each environment: QKb.cim-2B and QKb.cim-3D (Pop1), QKb.cim-3B1 and QKb.cim-5B2 (Pop2). Other than those four QTL, other QTL were detected in each population which were specific to environments: QKb.cim-5B1, QKb.cim-6A, and QKb.cim-7A (Pop1), QKb.cim-3B2, QKb.cim-4A1, QKb.cim-4A2, QKb.cim-4B, QKb.cim-5A1, QKb.cim-5A2, and QKb.cim-7A2 (Pop2). Among the four stable QTL, all but QKb.cim-3B1 were derived from the resistant parent. QKb.cim-2B and QKb.cim-3D in Pop1 and QKb.cim-3B1 and QKb.cim-5B2 in Pop2 explained 5.0–11.4% and 3.3–7.1% phenotypic variance, respectively. A combination of two stable QTL in each population reduced KB infection by 24–33%, respectively. Transgressive resistant segregants lines derived with resistance alleles from both parents in each population were identified. Single nucleotide polymorphism (SNP) markers flanking these QTL regions may be amenable to marker-assisted selection. The best lines from both populations (in agronomy, end-use quality and KB resistance) carrying resistance alleles at all identified loci, may be used for inter-crossing and selection of improved germplasm in future. Markers flanking these QTL may assist in selection of such lines.

Karnal bunt (KB) of wheat, caused by Tilletia indica , is one of the greatest challenges to grain industry, not because of yield loss, but quarantine regulations that restrict international movement and trade of affected stocks. Genetic resistance is the best way to manage this disease. Although several different sources of resistance have been identified to date, very few of those have been subjected to genetic analyses. Understanding the genetics of resistance, characterization and mapping of new resistance loci can help in development of improved germplasm. The objective of this study was to identify and characterize resistance loci (QTL) in two independent recombinant inbred lines (RILs) populations utilizing different wheat lines as resistance donors. Elite CIMMYT wheat lines Blouk#1 and Huirivis#1 were used as susceptible female parents and WHEAR/KUKUNA/3/C80.1/3∗BATAVIA//2∗WBLL1 (WKCBW) and Mutus as moderately resistant male parents in Pop1 and Pop2 populations, respectively. Populations were evaluated for KB resistance in 2015–16 and 2016–17 cropping seasons at two seeding dates (total four environments) in Cd. Obregon, Mexico. Two stable QTL from each population were identified in each environment: QKb.cim-2B and QKb.cim-3D (Pop1), QKb.cim-3B1 and QKb.cim-5B2 (Pop2). Other than those four QTL, other QTL were detected in each population which were specific to environments: QKb.cim-5B1, QKb.cim-6A , and QKb.cim-7A (Pop1), QKb.cim-3B2, QKb.cim-4A1, QKb.cim-4A2, QKb.cim-4B, QKb.cim-5A1, QKb.cim-5A2 , and QKb.cim-7A2 (Pop2). Among the four stable QTL, all but QKb.cim-3B1 were derived from the resistant parent. QKb.cim-2B and QKb.cim-3D in Pop1 and QKb.cim-3B1 and QKb.cim-5B2 in Pop2 explained 5.0–11.4% and 3.3–7.1% phenotypic variance, respectively. A combination of two stable QTL in each population reduced KB infection by 24–33%, respectively. Transgressive resistant segregants lines derived with resistance alleles from both parents in each population were identified. Single nucleotide polymorphism (SNP) markers flanking these QTL regions may be amenable to marker-assisted selection. The best lines from both populations (in agronomy, end-use quality and KB resistance) carrying resistance alleles at all identified loci, may be used for inter-crossing and selection of improved germplasm in future. Markers flanking these QTL may assist in selection of such lines. [ABSTRACT FROM AUTHOR]

Plasmopara halstedii was isolated from diseased sunflowers collected from eight locations in the Czech Republic from 2007 to 2014. Races of the pathogen were determined based on 84 isolates collected during the study. In total, eight races of P. halstedii were detected using a set of nine sunflower differential lines. Races 700, 704, 705, 710, 714 and 715 were proven by soil drench inoculation, and two additional races (730 and 770) proposed by the previously applied leaf disc inoculation method. Race 700 was the most dominant in the Czech P. halstedii populations, with race 710 being the second most frequent. Races 704 and 714 were found over three seasons, while other races were recorded only in one growing season (race 730 in 2010, and the new races 705 and 715 in 2014). A comprehensive study was further conducted for isolates collected in 2013-14 using an extended differential set consisting of 15 sunflower lines. According to the latter methodology which marks races with five-digit virulence codes, races 70060, 70471, 70571, 71060, 71461 and 71571 were recorded. The growing complexity of P. halstedii pathogenicity exhibited by the ability to infect higher numbers of differential genotypes and resulting in determination of the new pathogen races (virulence profiles) 70571, 71461 and 71571 is alarming. Although the limited number of isolates studied cannot characterize the entire pathogen diversity in the Czech Republic, the trend towards more diverse virulence in P. halstedii populations is clearly demonstrated by the new records of races 704, 705, 714 and 715, all capable of overcoming the resistance gene Pl 6. [ABSTRACT FROM AUTHOR]

Integrated protection represents a modern approach, denoting a protection strategy of agro-ecosystems; and it represents a complex system employing all appropriate methods in a manner as consistent and smooth as possible, in order to maintain the biocenotic balance of agrosystems and to keep pathogens at a level at which they do not cause economic damage (so-called level of eco-efficiency). A biocenotic approach to issues of agrosystem protection against disease attack requires an acknowledgement of all aspects regarding the evolution of pests in time and space, so as to be able to intervene at the right time with all possible means. And such protection measures are not supposed to restrain existing tendencies in the agrosystem. Therefore, this implies the awareness that any applied protection measures do not affect solely a certain pathogen, but the entire plant and animal community, as well as the soil and water.

In 2007-2012 the first detailed study of P. halstedii distribution and severity was performed in the Czech Republic by monitoring altogether 128 localities. Incidence of the pathogen was recorded at seven localities in south-eastern (Central and South Moravia) and central parts (East and Central Bohemia) of the country; at only four localities the occurrence of sunflower downy mildew symptoms and pathogen sporulation were recorded repeatedly. In all cases the primary infection prevailed, and the severity of infections was rather low. The majority of records were for sunflower experimental fields (e.g. fields of Central Institute for Supervising and Testing in Agriculture. Brno-Chrlice, Czech Republic), one record came from a commercial field and one record from a hobby field. Results of surveys indicate that reservoirs of primary inoculum likely exist in the soil contaminated by P. halstedii oospores in these habitats, but additional transfer by infected seed may be possible. Historical and geographical consequences of recorded infections are discussed, as well as virulence variation in the Czech pathogen populations which is currently in the process of investigation.

The in vitro and in vivo control of Phyllosticta citricarpa (citrus black spot, CBS) on citrus fruits was evaluated using 14 essential oils (EOs) extracted from Uruguayan native plants. In vitro, volatile components of Chenopodium ambrosioides completely inhibited fungal growth. The dilution agar test showed that fungus reproduction was completely inhibited by Conyza bonaerensis essential oil (EO). The other 12 EOs tested showed high inhibition after 10–15 d, presenting fungistatic effects. In vivo, assays were performed on fruit of lemon [ Citrus limon (L.) Burm] and Valencia orange [ Citrus sinensis (L.) Osbeck] in order to evaluate the effects of liquid and volatile EO phases on reproduction. Typical lesions of CBS without reproductive structures were exposed to Ch. ambrosioides and C. bonaerensis EOs for 20 d at 27 °C and cycles of 16 h light and 8 h dark. The volatile components of Ch. ambrosioides were able to control 100% of P. citricarpa reproduction in orange and lemon fruit. The growth of other fungi such, as Colletotrichum gloeosporoides and Fusarium sp., was also inhibited. Nevertheless, the liquid phase was not effective to control the pathogen. In another test, carton boxes with 20 fruits, each presenting typical CBS symptoms, but without the presence of reproductive structures, were exposed to 0.01 and 0.05% of Ch. ambrosioides EO (w/v). The fruits were stored at 5 °C for 20 d and then kept for 7 d at room temperature. A 40% reduction of reproduction was observed in citrus fruit exposed to 0.05% of EO. GC–MS analysis of EOs showed that Ch. ambrosioides EO was composed of 76% monoterpene compounds (49 and 27% of oxygenated and hydrocarbons, respectively), while C. bonaerensis EO presented 17% monoterpenes and 10% sequisterpenes. [ABSTRACT FROM AUTHOR]

Integrated protection represents a modern approach, denoting a protection strategy of agro-ecosystems; and it represents a complex system employing all appropriate methods in a manner as consistent and smooth as possible, in order to maintain the biocenotic balance of agrosystems and to keep pathogens at a level at which they do not cause economic damage (so-called level of eco-efficiency). A biocenotic approach to issues of agrosystem protection against disease attack requires an acknowledgement of all aspects regarding the evolution of pests in time and space, so as to be able to intervene at the right time with all possible means. And such protection measures are not supposed to restrain existing tendencies in the agrosystem. Therefore, this implies the awareness that any applied protection measures do not affect solely a certain pathogen, but the entire plant and animal community, as well as the soil and water. [ABSTRACT FROM AUTHOR]

In 2007-2012 the first detailed study of P. halstedii distribution and severity was performed in the Czech Republic by monitoring altogether 128 localities. Incidence of the pathogen was recorded at seven localities in south-eastern (Central and South Moravia) and central parts (East and Central Bohemia) of the country; at only four localities the occurrence of sunflower downy mildew symptoms and pathogen sporulation were recorded repeatedly. In all cases the primary infection prevailed, and the severity of infections was rather low. The majority of records were for sunflower experimental fields (e.g. fields of Central Institute for Supervising and Testing in Agriculture. Brno-Chrlice, Czech Republic), one record came from a commercial field and one record from a hobby field. Results of surveys indicate that reservoirs of primary inoculum likely exist in the soil contaminated by P. halstedii oospores in these habitats, but additional transfer by infected seed may be possible. Historical and geographical consequences of recorded infections are discussed, as well as virulence variation in the Czech pathogen populations which is currently in the process of investigation. [ABSTRACT FROM AUTHOR]