Relação entre cor de grão e resistência à germinação pré-colheita em trigo

Since red alleles (R) of the genes that control grain colour are important for the improvement of preharvest sprouting resistance in wheat and there are three independently inherited loci, on chromosomes 3A, 3B and 3D of hexaploid wheat, it is possible to vary the dosage of dominant alleles in a breeding program. The objective of this work was to evaluate the dosage effect of R genes on preharvest sprouting, in a single seed descent population, named TRL, derived from the cross between Timgalen, white-grained wheat, and RL 4137, red-grained wheat. The study was carried out using sprouting data in ripe ears obtained under artificial conditions in a rainfall simulator over three years. According to the results there is a significant effect on preharvest sprouting provided by colour and a weaker effect of increasing R dosage. However, the significant residual genotypic variation between red lines and all lines (reds and whites) at 0.1% level showed that preharvest sprouting was also controlled by other genes. There are no significant correlations between sprouting and date of ripeness or between ripeness, R dosage and colour intensity.Uma vez que os alelos dominantes para cor vermelha (R), dos genes que controlam a cor do grão, têm importância no incremento da resistência à germinação pré-colheita, em trigo, e há três locos herdados independentemente, nos cromossomos 3A, 3B e 3D do trigo hexaplóide, é possível variar sua dosagem em um programa de melhoramento. O objetivo deste trabalho foi avaliar o efeito de dosagem dos genes R na germinação pré-colheita, em uma população de descendência por semente única, batizada de TRL, derivada do cruzamento entre Timgalen, trigo de grão branco, e RL 4137, trigo de grão vermelho. O estudo utilizou dados de germinação em espigas maduras, obtidos sob condições artificiais em um simulador de chuva, em três anos. De acordo com os resultados, o efeito da cor de grão e, menos acentuadamente, da dosagem dos alelos dominantes, sobre a germinação pré-colheita foi significativo. Entretanto, a variação genotípica residual, entre as linhas vermelhas e entre as linhas vermelhas e brancas, significativa a 0,1%, mostra que a germinação pré-colheita é também controlada por outros genes. Não foi constatada correlação significativa entre germinação na espiga e data de maturação ou entre maturação, dosagem de R e intensidade de cor

Analysis of preharvest sprouting in three Brazilian wheat populations

O objetivo deste trabalho foi avaliar a possibilidade de obtenção de linhas recombinantes homozigotas de trigo mais resistentes à germinação pré-colheita independentemente dos genes de cor, em três populações brasileiras de grãos vermelhos. Os resultados mostraram significância estatística entre linhas, em todas as populações, distribuição normal e segregação transgressiva. A distribuição normal apresentada por todas as populações com grãos vermelhos sugere que a germinação pré-colheita, excluindo-se os genes responsáveis pela pigmentação dos grãos, é, provavelmente, controlada por muitos genes. Os resultados indicam, também, que é possível aumentar a resistência à germinação pré-colheita, independentemente dos genes de cor.The objective of this work was to evaluate the possibility of obtaining recombinant inbred wheat lines more resistant to preharvest sprouting, independently of colour genes, in three red-grained Brazilian wheat populations. The results showed statistical significance among lines within all populations, which presented a normal distribution and transgressive segregation for preharvest sprouting. The normal distribution of the lines from all red-grained populations suggests that sprouting, excluding the genes expressing seed coat pigmentation, is, probably, controlled by many genes. These findings also indicate that it may be possible to improve resistance to preharvest sprouting, independently of the colour genes

The error of our ways: the experience of self-reported position in a location-based game

We present a study of people’s use of positional information as part of a collaborative location-based game. The game exploits self-reported positioning in which mobile players manually reveal their positions to remote players by manipulating electronic maps. Analysis of players’ movements, position reports and communications, drawing on video data, system logs and player feedback, highlights some of the ways in which humans generate, communicate and interpret position reports. It appears that remote participants are largely untroubled by the relatively high positional error associated with self reports. Our analysis suggests that this may because mobile players declare themselves to be in plausible locations such as at common landmarks, ahead of themselves on their current trajectory (stating their intent) or behind themselves (confirming previously visited locations). These observations raise new requirements for the future development of automated positioning systems and also suggest that selfreported positioning may be a useful fallback when automated systems are unavailable or too unreliable

The wheat Phs-A1 pre-harvest sprouting resistance locus delays the rate of seed dormancy loss and maps 0.3 cM distal to the PM19 genes in UK germplasm

The precocious germination of cereal grains before harvest, also known as pre-harvest sprouting, is an important source of yield and quality loss in cereal production. Pre-harvest sprouting is a complex grain defect and is becoming an increasing challenge due to changing climate patterns. Resistance to sprouting is multi-genic, although a significant proportion of the sprouting variation in modern wheat cultivars is controlled by a few major quantitative trait loci, including Phs-A1 in chromosome arm 4AL. Despite its importance, little is known about the physiological basis and the gene(s) underlying this important locus. In this study, we characterized Phs-A1 and show that it confers resistance to sprouting damage by affecting the rate of dormancy loss during dry seed after-ripening. We show Phs-A1 to be effective even when seeds develop at low temperature (13 °C). Comparative analysis of syntenic Phs-A1 intervals in wheat and Brachypodium uncovered ten orthologous genes, including the Plasma Membrane 19 genes (PM19-A1 and PM19-A2) previously proposed as the main candidates for this locus. However, high-resolution fine-mapping in two bi-parental UK mapping populations delimited Phs-A1 to an interval 0.3 cM distal to the PM19 genes. This study suggests the possibility that more than one causal gene underlies this major pre-harvest sprouting locus. The information and resources reported in this study will help test this hypothesis across a wider set of germplasm and will be of importance for breeding more sprouting resilient wheat varieties

An analysis of dormancy, ABA responsiveness, after-ripening and pre-harvest sprouting in hexaploid wheat (Triticum aestivum L.) caryopses

Embryo and caryopsis dormancy, abscisic acid (ABA) responsiveness, after-ripening (AR), and the disorder pre-harvest sprouting (PHS) were investigated in six genetically related wheat varieties previously characterized as resistant, intermediate, or susceptible to PHS. Timing of caryopsis AR differed between varieties; AR occurred before harvest ripeness in the most PHS-susceptible, whereas AR was slowest in the most PHS-resistant. Whole caryopses of all varieties showed little ABA-responsiveness during AR; PHS-susceptible varieties were responsive at the beginning of the AR period whereas PHS-resistant showed some responsiveness throughout. Isolated embryos showed relatively little dormancy during grain-filling and most varieties exhibited a window of decreased ABA-responsiveness around the period of maximum dry matter accumulation (physiological maturity). Susceptibility to PHS was assessed by overhead misting of either isolated ears or whole plants during AR; varieties were clearly distinguished using both methods. These analyses allowed an investigation of the interactions between the different components of seed development, compartments, and environment for the six varieties. There was no direct relationship between speed of caryopsis AR and embryo dormancy or ABA-responsiveness during seed maturation. However, the velocity of AR of a variety was closely associated with the degree of susceptibility to PHS during AR suggesting that these characters are developmentally linked. Investigation of genetic components of AR may therefore aid breeding approaches to reduce susceptibility to PHS

Mapping genes for resistance to sprouting damage in wheat

A series of experiments to investigate the genetic basis of pre-harvest sprouting are reported. The results are combined with previously published studies in a composite genetic map for sprout resistance in hexaploid wheat. Different studies, using classical genetics, aneuploids, chromosome substitutions, or QTL mapping, have identified various regions of the A, B, and D genomes affecting dormancy. Comparisons between the available studies lead to the following conclusions: • Different studies often identify different genetic loci, in part reflecting different sampling from the available gene pool. This implies that many loci are involved in determining resistance, and that new loci may be discovered as the number of mapping studies increases.• There are, however, examples where similar map locations are implicated over different crosses. These may reflect the detection of key resistance genes. • Finally, (genotype × environment) interactions are frequently observed. The implications of these observations for crop improvement and research programmes are discussed