Authors:A. Ficsor, J. Bakonyi, M. Csősz, A. Tomcsányi, J. Varga, and B. Tóth
Net blotch and leaf stripe caused by Pyrenophora teres and P. graminea, respectively, are two major foliar diseases of barley. These two species are able to infect wheat, too. The species composition of these pathogens was examined, for the first time, in four different regions of Hungary in 2006–2010. Altogether 204 isolates were obtained from 99 winter barley, 55 spring barley and 50 wheat leaf samples collected in commercial fields and experimental stations, and species assignment was carried out using species-specific PCR reactions. Most isolates belonged to P. teres f. teres (68%), 26% to P. teres f. maculata and only 6% of the isolates were assigned to P. graminea. Interestingly, all but one of the P. graminea isolates came from the western part of Hungary, while both forms of P. teres occurred in each region. The distribution of mating type genes was also examined in 144 isolates. The overall ratio of MAT1 and MAT2 genes in P. graminea, P. teres f. maculata and P. teres f. teres was 5:3, and close to 2:1 and 1:1, respectively. Both MAT1 and MAT2 isolates of each fungal species/form were distributed in almost all regions over several years, indicating a high potential for sexual outcrossing within local populations of these pathogens. Our survey may be helpful to determine priorities in disease resistance breeding programs. Further studies are in progress to examine the population structure of the most abundant pathogen P. teres f. teres.
Authors:Y. Gao, Q. Sun, R. Wang, J. Feng, F. Lin, N. Cui, X. Chen, S. Xu, Y. Bai, and X. Xu
Stripe rust, caused by Puccinia striiformis Westend. f. sp. tritici Eriks., is a major disease that causes substantial losses to wheat production worldwide. The utilization of effective resistance genes in wheat cultivars is the preferred control of the disease. To study the inheritance of all-stage resistance in spring wheat cultivars Louise, WA008016, Express, Solano, Alturas and Zak from the Pacific Northwest (PNW) of the United States, the six cultivars were crossed with the Chinese susceptible variety Taichung 29. Single-spore isolates of CYR32 and CYR33, the predominant Chinese races of P. striiformis f. sp. tritici, were used to evaluate F1, F2 and BC1 generations for stripe rust resistance under controlled greenhouse conditions. Genetic analysis determined that Louise had one dominant resistance gene to CYR32, temporarily designated as YrLou. WA008016 had two dominant and one recessive resistance genes to CYR32, temporarily designated as YrWA1, YrWA2 and YrWA3, respectively. Express had a single recessive gene that conferred resistance to CYR32, temporarily designated as YrExp3. The two independent dominant genes in Solano conferring resistance to CYR32 were temporarily designated as YrSol1 and YrSol2. Alturas had two recessive genes for resistance to CYR32, temporarily designated as YrAlt1 and YrAlt2. Zak has one dominant gene for resistance to CYR33, temporarily designated as YrZak1. These six cultivars can be important resistance sources in Chinese wheat stripe rust resistance breeding.
Authors:J. Chrpová, V. Šíp, L. Štočková, and V. Dumalasová
Resistance of 28 winter wheat cultivars registered in the Czech Republic and ten potential sources of resistance to Fusarium head blight (FHB) was evaluated after artificial inoculation with Fusarium culmorum in field trials lasting for three years (2008, 2009, 2010). The data on deoxynivalenol (DON) content were supplemented by symptom scores and determination of% of Fusarium damaged grains and% reductions of grain weight per spike due to infection. The examined traits were significantly interrelated and showed high variation in all years. Significantly lower DON content, combined with relatively lower manifestation of the disease was observed in the modern, commercially grown cultivars Bakfis, Graindor, Sakura and Bodycek (catalogued in the Official Journal of EU), besides Novokrymka 102, PI 166910 (line resistant to dwarf and common bunt) and Arina, which could be effectively used in resistance breeding. However, the experiments performed under high infection pressure were also able to reveal high susceptibility to FHB in some commercially grown wheat cultivars, which may pose a serious threat to wheat production.
Some wild species of the genus Oryza such as O. rufipogon and O. longistaminata show a high level of resistance to pests and diseases including rice blast (caused by Magnaporthe grisea). To transfer blast resistance from wild species into cultivatedvarieties (O. sativa), interspecific hybrids were produced and anther culture was used toaccelerate the procedure of resistance breeding. Anther culture efficiency depended onboth the medium and the genotype of the cultivated varieties and the wild species. Afterinoculation with a mixture of six strains with wide spectrum virulence, all the F1 hybridswere resistant to blast; the F2 plants segregated, from high resistance to susceptibility, anda similar result was obtained for the H1 and H2 plants. At the H3 stage, blast resistancetended to be stable and almost 100% of inoculated H5 plants were highly resistant to riceblast. For agronomic characteristics, the F2 and H1 showed segregation, but no significantdifferences were seen between the cultivated parents and the H2 to H5 generations. Theresults demonstrate that blast resistance genes can be transferred from wild rice speciesinto cultivated varieties through crossing and anther culture, and the H5 can be used asstable lines in future breeding programmes.
Authors:Cs. Bojtor, Z. Győri, P. Sipos, L. Radócz, and B. Tóth
The aim of the study was to investigate changes of photosynthetic efficiency, amount of photosynthetic pigments, superoxide dismutase (SOD) enzyme activity, and rate of lipid peroxidation in bean-rust interaction. The clarification of the role of the above changes involved in the defence mechanism can significantly contribute to the breeding of plant varieties with natural resistance. Consequently, the amount of chemicals used in food production can be significantly reduced. In the present study some principal physiological parameters, such as the relative chlorophyll content of the host plant, the amount of photosynthetic pigments, changes in photosynthetic efficiency, and the activity of superoxide-dismutase (SOD) in addition to rate of lipid peroxidation (LP) were measured. The experiment was conducted in a humidity tent. Significant decrease in the relative chlorophyll content and in the amount of photosynthetic pigments was measured. At both sampling times, an increase was found in superoxide-dismutase enzyme activity and in rate of lipid peroxidation due to the bean rust infection. Notably, in several cases the differences were significant. The results indicate that the above parameters have important role in the bean-rust interaction, which should be taken into consideration in resistance breeding.
One important aim of hybrid breeding is to exploit the heterosis effect appearing in the F1. Nevertheless, the breeders of commercial F1 hybrids have no real information on the extent of heterosis manifested in the combinations they produce, since the mean value of the combination in question is never compared with that of the parents or of the better parent, but only with that of the most popular control variety it is hoped to surpass. The complex variety value of a new hybrid should be greater than that of the control. In the case of pepper hybrids the factors that make up the complex variety value can be divided into four groups: the early and total yield potential predicted from the individual value of the parents (P), special consumption and production traits resulting in F1 quality (Q), F1 resistance value (R) and the heterosis effect (H). The importance of these four factors in the complex variety value of a given pepper hybrid may be summed in innumerable variations, but the individual yield potential and quality traits of the parents are of outstanding importance. This is the basis, without which combining ability, resistance value and heterosis effect will remain unexploited. When selecting pepper lines for combining ability, risks may be involved in over-strict selection for general combining ability alone, so a combined crossing system involving a carefully constructed partial diallel is normally employed to obtain information on the general combining ability of lines preliminarily screened for individual plant performance and on the specific combining ability of their combinations. Cross-breeding aimed at the development of parental lines and constant varieties makes use of single crosses, crossing series, backcrossing and resistance breeding.
Large numbers of genetically stable, homozygous plants are needed for classical and molecular breeding programmes. In vitro anther culture has proved to be a useful tool for haploid/doubled haploid (DH) induction in pepper (Capsicum annuum L.) for more than twenty years. The present paper reports on a great improvement in the in vitro haploid induction and genome duplication methods routinely used for resistance breeding in sweet and spice peppers by two Hungarian research institutions, the Agricultural Biotechnology Center in Gödöllő and the Budapest Research Unit of the Vegetable Crops Research Institute. As a result of the colchicine-stimulated early genome induction method, the critically low (<0.1%) regeneration frequency of spice pepper types became ten times greater, reaching a value of around 1.0%, though this was still considerably lower than that achieved in pepper varieties for fresh consumption (5-10%). Moreover, the ratio of useful doubled haploids was far higher (H:DH = 1:2 or 1:4) in some cases after colchicine treatment than that of untreated control plants (H:DH = 2:1 or 3:1, depending on the genotype). An efficient method with good reproducibility, requiring less manual work, was elaborated for the in vitro genome duplication of pepper haploid regenerants using colchicine. When the haploid induction ability of plants conventionally cultured in the greenhouse was compared to that of plants raised under artificial conditions in phytotron chambers (satisfactory day and night temperatures, illumination, humidity), the responsiveness of the latter microspores (ratio of plant regeneration) was found to be almost twice as high. The application of 3% maltose for six days at 35°C resulted in a 1.45% increase in the ratio of responding anthers and a 0.34% increase in plant regeneration, averaged over all the variety types. Phenosafranin staining was used for the analysis of microspore viability. The reduction in viability during the induction period proved to be less pronounced in lines with better androgenetic responses than in those with poorer responsiveness.