196,271 research outputs found
Quantitative Trait Loci (QTLs) for pollen thermotolerance detected in maize
No full textPollen thermotolerance is an important component of the adaptability of crops to high temperature stress. The tolerance level of the different genotypes in a population of 45 maize recombinant inbred lines was determined as the degree of injury caused by high temperature to pollen germinability (IPGG) and pollen tube growth (IPTG) in an in vitro assay. Both traits revealed quantitative variability and high heritability. The traits were genetically dissected by the analysis of molecular markers using 184 mapped restriction fragment length polymorphisms (RFLPs). Significant genetic correlation between the markers and the trait allowed us to identify a minimum number of five quantitative trait loci (QTLs) for IPGG and six QTLs for IPTG. Their chromosomal localization indicated that the two characters are controlled by different sets of genes. In addition, IPGG and IPTG were shown to be basically independent of the pollen germination ability and pollen tube growth rate under non-stress conditions. These results are discussed in relation to their possible utilization in a breeding strategy for the improvement of thermotolerance in maize
Quantitative expression of maize HSPs : genetic dissection and association with thermotolerance
No full textIn higher plants, within-species qualitative polymorphism for heat shock proteins (HSPs) is extremely rare, even between genotypes showing different heritable levels of thermotolerance. Here we have explored the amount of quantitative variability in HSP synthesis in maize. We have analyzed the quantitative expression of the typical HSPs in a set of recombinant inbreds (RIs) derived from the f1 hybrid between a thermotolerant (T232)- and a thermosensitive (CM37)-genotype, characterized for about 200 mapped RFLP loci. Significant differences were detected in the level of expression of five HSPs, and their frequency distribution in the RI population is that of a quantitative trait. Subsequent mapping of loci controlling the characters, based on RFLP analysis, confirmed the multigenic control of HSP expression: the regression analysis of the band intensities of each variant HSP on RFLPs revealed, for the different HSPs, a minimum number of three to eight quantitative trait loci (QTLs) accounting for a high proportion (0.35-0.60) of the genetic variability of these bands. An analysis of the correlation between the variability of HSPs and that of cellular membrane stability, a cellular component of thermotolerance, did not reveal any significant association of the two parameters
Γ-X mixing of the free and bound exciton in GaAs1-xPx
No full textPhotoluminescence in GaAs1-xPx near crossover at liquid He temperature gives evidence of a Γ-x interaction of the bound and free exciton. The interaction in the FE case is made possible by the breaking down of the translational symmetry of the Hamiltonian due to fluctuations in the random-alloy potential. The matrix elements of such interaction are found equal to 0.5 and 3.5 meV for the free and donor-bound exciton respectively
Studium Urbis e Studium Curie nel Trecento e nel Quattrocento: linee di politica culturale
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