The resistance genes Lr9, Lr24, Lr25, Lr29, Lr35 and Lr37, which were not previously utilised in Hungary, have been incorporated into four Martonvásár winter wheat cultivars using markerassisted selection with PCR-based markers. In the course of a backcross programme, the genes were transferred into Martonvásár wheat varieties and various BC generations were produced. Work aimed at pyramiding resistance genes is currently underway in Martonvásár, and plants containing the gene combinations Lr9 ? Lr24, Lr9 ? Lr25 and Lr9 ? Lr29 are now available. From the BC 2 F 4 generation of the 'Mv Emma'*3/'R.L.6010' combination ('R.L.6010' is the donor of the Lr9 gene) 287 lines were tested for leaf rust resistance in an artificially inoculated nursery. A co-dominant primer combination was designed to identify both resistant and susceptible offsprings. The results of resistance tests and molecular marker detection agreed in most cases. Designated leaf rust resistance genes were identified with molecular markers in wheat varieties and breeding lines. The Lr26 and Lr34 resistance genes occur frequently in the Martonvásár gene pool, and the presence of the Lr37 gene has also been detected in a number of Hungarian genotypes.
Pea (Pisum sativum L.) cv. Afghanistan inoculated with Rhizobium leguminosarum biovar. viciae aborts the nodulation process if North American strains are used but will form effective nodules with strain TOM. Early nodulins (nodule specific root proteins) were examined by in vitro translation of total root or root + nodule RNA and two-dimensional gel analysis. Qualitatively different protein patterns were found between effective nodulation in Trapper (a North American variety) and 'Afghanistan' and between effective and abortive nodulation in 'Afghanistan'. Six days after inoculation a 26-kDa protein was evident that was only produced in Trapper roots and several nodulins were visible. Nodulin N-37 was present in effective and abortive combinations. Nodulin N-52 was present in inoculated Trapper but not in inoculated 'Afghanistan', whereas N-23 was present in inoculated 'Afghanistan' but not in inoculated Trapper. Nodulin N-58 occurred only in abortive combinations with 'Afghanistan'. Nonnodulating Trapper (Trapper into which the nonnodulation genes of 'Afghanistan' had been back-crossed) showed the same patterns of gene expression as 'Afghanistan'. The expression of several genes apparently differs between 'Afghanistan' and Trapper for the nodulation process.
Pisum sativum L., cv. Afghanistan, does not form nodules with 128C52, a North American strain of Rhizobium leguminosarum. Timing of the abortion of the nodulation process was determined by microscopy in both 'Afghanistan' and nonnodulating 'Trapper,' produced by backcrossing the nonnodulating genes of 'Afghanistan' into 'Trapper,' a North American variety. Three to 5 days after inoculation, we observed deformed roots and localized swellings as well as loosely curled root hairs in these nonnodulating combinations. Rhizobia entered root hairs and epidermal cells, but no infection threads were seen. Cortical cells divided and a nodule meristem was initiated. Some meristematic cells showed abnormal features such as a high concentration of free ribosomes, dilated endoplasmic reticulum often connected to a dilated nuclear envelope, and disrupted mitochondria. Cortical cells around the nodule meristem were devoid of starch grains. Such phenotypes are known to be associated with rhizobial mutants, but in this case a plant effect is responsible.
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