The Colorado potato beetle, Leptinotarsa decemlineata (Say), is a serious, widely distributed pest of potato and other crops. This pest is able to defoliate the host plant and cause severe yield loss. Moreover, the pest quickly becomes resistant to many chemical pesticides. Therefore, the development of novel biopesticides targeting this pest is urgently needed. The purpose of this study was to obtain new strains of the entomopathogenic fungus Beauveria bassiana and assess their efficacy against L. decemlineata adults under laboratory conditions. Twelve strains were isolated from cadavers of Colorado potato beetles collected in potato fields in the Czech Republic. Test beetles were treated by suspensions of conidia at the concentration of 1 × 107 spores per milliliter and their survival was recorded daily for three weeks. The results of the bioassays revealed that all new native strains were pathogenic to L. decemlineata adults and caused mortality up to 100% at the end of the trial period with an LT50 of about 7 days. These strains were more virulent than a reference strain GHA and some of them can be recommended for the development of a new mycoinsecticide against L. decemlineata. Our findings also highlight the importance of searching for perspective strains of entomopathogenic fungi among naturally infected hosts.
The bulb mite, Rhizoglyphus robini, is a serious pest of garlic, onion and other crops. The mite is usually found in association with dangerous fungal pathogens such as Fusarium spp. Control of this pest has relied upon the use of synthetic acaricides but chemical control of the bulb mite is difficult because it is able to develop resistance quickly. Thus, alternative control methods, e.g. biological control, need to be developed and implemented. The aim of this study was to assess efficacy of selected strains of entomopathogenic fungi (EPF) against adult females of R. robini under laboratory conditions. New EPF strains were isolated from soil samples collected in onion and garlic fields in the Czech Republic and Israel using soil elution and cultivation on selective media. Fungal species were determined using macroscopic, microscopic and molecular markers. The efficacy against R. robini females was tested in 17 isolated and 3 reference strains of EPF. Results revealed high variability among species and strains. The highest efficacy against R. robini mites was found in strains of Metarhizium anisopliae isolated from soil samples collected in the Czech Republic which caused mortality up to 99.3%, and a Metarhizium indigoticum strain from Israel causing 98.3% mortality after four days of bioassay. Isaria fumosorosea strains did not caused mortality higher than 40%. The lowest virulence was found in Beauveria spp. strains causing mortality of mites between 5 and 25%. Median lethal time (LT50) and median lethal concentration (LC50) in the three most virulent strains ranged between 2 and 4 days and between 1.01×104 and 2.36×105 spores/ml, respectively. The concentration-response models indicated that the M. indigoticum strain is more lethal than M. anisopliae strains. The present study showed that some strains of entomopathogenic fungi, especially from the genus Metarhizium, could be perspective biocontrol agents against R. robini.
The selection of desirable genotypes with recessive characteristics, such as self-incompatible plants, is often difficult or even impossible and represents a crucial barrier in accelerating the breeding process. Molecular approaches and selection based on molecular markers can allow breeders to overcome this limitation. The use of self-incompatibility is an alternative in hybrid breeding of oilseed rape. Unfortunately, stable self-incompatibility is recessive and phenotype-based selection is very difficult and time-consuming. The development of reliable molecular markers for detecting desirable plants with functional self-incompatible genes is of great importance for breeders and allows selection at early stages of plant growth. Because most of these reliable molecular markers are based on discrimination of class I S-locus genes that are present in self-compatible plants, there is a need to use an internal control in order to detect possible PCR inhibition that gives false results during genotyping. In this study, 269 double haploid F2 oilseed rape plants obtained by microspore embryogenesis were used to verify the applicability of an improved PCR assay based on the detection of the class I SLG gene along with an internal control. Comparative analysis of the PCR genotyping results vs. S phenotype analysis confirmed the applicability of this molecular approach in hybrid breeding programs. This approach allows accurate detection of self-incompatible plants via a different amplification profile.
Until now in Europe has not been cultivated any hybrid cultivar of oilseed rape based on the Shaan 2A cytoplasmic male sterility (CMS), a widely used CMS system in China. The aim of Czech breeders now is to produce new, improved cultivars of rapeseed based on this CMS system. Sterile Shaan 2A CMS line (S; rf/rf), its corresponding maintainers (N; rf/rf) and fertility restorers (S; Rf/Rf) were analyzed on molecular level for the presence of functional CMS cytoplasm. Two new primer pairs covering CMS-associated gene (so called orf224-1) present in Shaan 2A CMS line were developed and selection capability of the developed primers was successfully evaluated. These primers can be used for early selection of plants with functional Shaan 2A CMS system in breeding programmes.
Havlíčková L., Jozová E., Rychlá A., Klíma M., Kučera V., Čurn V. (2014): Genetic diversity assessment in winter oilseed rape (Brassica napus L.) collection using AFLP, ISSR and SSR markers. Czech J. Genet. Plant Breed., 50: 216-225.The genetic diversity of 94 accessions of winter oilseed rape (Brassica napus L.), representing past and contemporary material utilized in the Czech breeding programmes, was determined using microsatellites (SSRs), ISSRs and AFLPs. All three kinds of markers differed in the range of observed polymorphism and differentiated clearly each accession. Altogether 89 SSR, 1003 AFLP and 53 ISSR markers were evaluated. Their average rates of polymorphic bands were 100%, 53.9% and 90.6%, respectively, indicating high genetic diversity among the accessions. The greatest genetic distance was found by ISSRs (62.3%) whereas significantly lower distances of 49.4% in SSRs and 35.5% in AFLPs were observed. The genetic similarity matrix clearly distinguished all accessions. A set of the most distinct varieties was established. The analysis of the genetic pattern of the accessions indicated two groups comprising most of the modern Czech breeding materials, revealing a distinct shift in breeding. Surprisingly, molecular analyses did not support breeders' views about a narrow genetic base of the Czech breeding materials. The choice of appropriate technology for different aspects of germplasm evaluation is also discussed.
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