Production and identification of doubled haploids in tropical maize.
The production of maize doubled haploid (DH) lines is a technique commonly used by private companies, but not by Brazilian public institutions. Research on this technique is essential to develop and improve the production of DH lines grown under tropical conditions. We assessed the ability of a gynogenetic haploid inducer system to induce haploids in a tropical environment, assessed the induction rate of haploids identified using the R-navajo morphological marker, checked for interference from the generation of hybrid donors on haploid induction, measured the ability of flow cytometry, and simple sequence repeat marker techniques to identify doubled haploids. Seeds from the inducer Krasnodar Embryo Marker Synthetic (KEMS) line were sown in Ponta Grossa, PR, and Cravinhos, SP, and the plants were crossed to produce six hybrids and their F2 generations. The seeds were separated according to the R-navajo morphological marker indicator of haploidy (purple endosperm and white embryo) and germinated in a controlled environment. Chromosomal duplication was performed in seedlings selected as putative haploids. We performed subsequent confirmation of ploidy and the success of duplication using flow cytometry and SSR marker techniques. We concluded that DH lines can be obtained from hybrids crossed with the inducer KEMS line. The generation of inbred hybrids did not affect the induction rate or chromosomal duplication in haploids. The use of flow cytometry and SSR markers was effective in verifying chromosomal duplication in haploids.
Informações fenotípicas e marcadores microssatélites de QTL na escolha de populações segregantes de feijoeiro
The objective of this work was to select promising common bean segregant populations for grain yield and polymorphic to microsatellite markers for grain yield QTL previously identified. Fourty nine lines were utilized and evaluated in two field trials in a triple lattice. Seven lines were selected and intercrossed in a diallel scheme and genotyped with 24 single sequence repeat (SSR) markers associated to grain yield QTL previously identified. Populations were evaluated in a randomized block design with three replications. Significant differences in the general and specific combining ability were observed, and the non-additive effects were highest. The outstanding lines were RC1-10 and Z-9 due to the highest gi values. Twenty five percent of the markers were polymorphic. Four populations were chosen for selecting families based on the line evaluations, the diallel analysis and the polymorphism of SSR markers. Among the segregant populations, RC1-10 x Z-9 is remarkable for having high CEC, high grain yield of the Carioca type, and their parents expressed high CGC. Considering the low number of polymorphic microsatellite markers in each population, it is necessary to use higher number of microsatellite markers associated to grain yield QTL.
Comparison of Binaural Release from Forward Masking in Animals and Humans. Electrophysiological Studies
Evoked potentials in the inferior colliculus and auditory areas of the cortex were studied in anesthetized guinea pigs and long-latency auditory evoked potentials (LAEP) were studied in waking humans using sequential binaural presentation of pairs of clicks – the masker and the masked signal – with a variable interval between them, to provide the conditions needed for the psychophysical phenomenon of direct forward masking. Introduction of phase differences between the masker and the masked signal led to decreases in suppression of responses to the masked signal and to faster recovery of the reaction types recorded. The greatest relative differences between response magnitudes to antiphase and synphase masked signals were seen at the beginning of the recovery process, and were 1.6, 1.5, and 1.4 respectively for responses from the inferior colliculus, auditory area of the cortex, and LAEP at stimulus intensities of 50–65 dB sound pressure level, differences subsequently decreasing to zero. There was a positive correlation between this measure and the stimulus intensity. The greatest differences between the time at which the recovery process ended for responses to antiphase and synphase masked signals were 4, 250, and about 2000 msec respectively for the inferior colliculus, auditory area of the cortex, and LAEP.