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Dokonano próby wprowadzenia genów odporności na porastanie z odpornej linii wsobnej Ot1-3 do odmian krajowych żyta ozimego. W tym celu otrzymano mieszańce BC2 odmian Dańkowskie Złote, Wibro, Warko, Amilo, Dańkowskie Nowe z linią wsobną i w dalszych pokoleniach (F1–F6) prowadzono selekcję w kierunku odporności na porastanie i przywrócenia pozostałych cech odmianowych. Większość wyselekcjonowanych rodów wraz z wysoką odpornością odziedziczyła niekorzystne cechy linii Ot1-3, rzutujące na niską przydatność hodowlaną. Odporne na porastanie i dobrze plonujące, na poziomie odmiany rodzicielskiej, rody otrzymano jedynie w potomstwie mieszańca z udziałem odmiany Wibro. Ród A100 odznaczał się wysoką liczbą opadania, dorównując pod tym względem odmianie Amilo, natomiast ród A94 wykazywał najwyższy stopień odporności na porastanie.
Main achievements in revealing the complex genetic background of cereal sprouting are reviewed. In spite of the identification of some morphological, anatomical, biochemical and molecular mechanisms and genes underlying sprouting we are still far from satisfactory understanding of causes that make particular genotypes resistant to precocious initiation of metabolic processes leading to germination of grains in ears. Current knowledge allows to assume polygenic control of sprouting with the main effect of a few major genes such as: R alleles encoding red grain colour, giberellin-insensitive Rht genes or Vp1 gene underlying sensitivity to abscisic acid (ABA). Depending on the species and variety the resistance mechanism may represent: long dormancy, reduced contactof anembryo with water and oxygen, aleuroneand embryo sensitivity to GA and ABA, high inhibitor content or decreased amylase diffusion through the endosperm cells. The main breeding perspective is to combine several mechanisms of resistance in a given variety. Thiscan beachieved by applying different gene sources and strategies of selection, including molecular marker assisted selection and biotechnology.
Molecular markers are modern diagnostic tools, which may help breeders to solve practical problems. They facilitate cultivar Identification, the determination of genetic similarities among breeding stocks and enable the calculation of polymorphism level, heterozygosity or self-pollination rate. But the main expectation with respect to molecular markers is their potential use in marker-assisted selection (MAS). There are four major strategies of finding a molecular marker tightly linked to a target gene of agronomie importance. The first approach takes advantage of the nearly isogenic lines (NILs) which are differentiated only by the allelic sets in the gene of interest and in the adjacent chromosomal region. The second strategy involves bulked segregant analysis (BSA) for identification of markers linked to a single gene. The third involves the genetic dissection of more complex traits, which leads to the identification of quantitative trait loci (QTL) and their markers. The fourth strategy of marker identification includes computer databases (sequence and mapping data). The usefulness of these strategies is discussed in this paper. Some consequences of the application of BSA for gene tagging are described.
Genetic maps containing molecular markers are useful tools for the identification of genes underlying quantitative traits (QTLs). Three traits important for plant physiology, i.e. chlorophyll content, sensitivity to GA and sensitivity to ABA, were evaluated for 99 F2 families of the DS2 x RXLl0 rye mapping population. The observed variation in the chlorophyll content in rye leaves was shown to be under the genetic control of four independent QTLs. They were located on the following chromosome arms: 1RL (QChc-1R.I), 3RS (QChc-3R.1), 4RL (QChc-4R.1) and 5RL (QChc-5R.1) The marker-assisted selection of recombinants comprising positively-acting alleles at these loci may significantly increase the chlorophyll content in rye leaves, which should result in a higher efficiency of photosynthesis. A decreasing of plant height in rye is one of the major aims of breeders selecting for lodging resistance. The polymorphism of genes controlling sensitivity to gibberellic acid may be the basis for a potential selection strategy. Three QTLs underlying the sensitivity of rye seedlings to GA were located on chromosomes 5RL (QGar-5R.I), 1RL (QGar-1R.1) and on 7RL (QGar-7R.I). The dwarfing allele of a Dw1 locus present in line RXL10 was mapped in the same position as the QGar-5R.1 gene. Sensitivity to ABA plays an important role in imposing dormancy in rye grain. Three QTLs affecting sensitivity to ABA were found. They were mapped on chromosomes 1RS (QAbr-1R.1), 2R in the centromeric region (QAbr-2R.1) and on 5RL (QAbr-5R.1). QAbr-5R.1, Dw1 and QGar-5R.1 are located in the same position on the distal part of the 5RL chromosome arm, which suggests that they belong to a single locus for a major regulatory gene controlling the development of rye plants.
Genetic control of a-amylase activity in rye grain was investigated by QTL mapping/based on DS2 x RXL10 intercross consisting of 99 F₅₋₆ families propagated at one location during four vegetation seasons. A wide range of variation in α-amylase activity and transgression effects were found among families and parental lines. This variation was shown to be determined in 40.1 % by 7 significant (LOD score not less than 2.5) and 2 putative QTLs (2 < LOD < 2.5) distributed on all rye chromosomes except 4R. Two significant QTLs located on 3RL and 5RL chromosome arms were expressed each year. The third significant QTL was detected in three years (1RL). The other four significant QTLs (2RL, 5RS, 6RL, 7RL) were found in one year of study. The number and composition of QTLs were specific for a given year varying from three to six. QTLs were not correlated with isoenzyme polymorphisms at the structural α-Amyl loci. A QTL associated with a region containing the α-Amy3 locus was detected on chromosome 5RL. Both high- and low-activity QTL alleles were found in each parental line, which explains the appearance of transgressive recombinants in the segregating population.
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