Abstract
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.
Highlights
In Brazil it is possible to grow two crops in each year
The results indicate that dominant R alleles from diverse varieties all have functionally equivalent effects on dormancy, which are expressed via the seedcoat as a pleiotropic effect of red pigmentation
From the F6 generation until F9, plants were derived by single seed descent (SSD) and a total of 90 recombinant inbred lines (RIL) were obtained, each derived from a different F2 segregant
Summary
In Brazil it is possible to grow two crops in each year. Wheat is sown in autumn, shortly after the summer harvest, and all cultivars are spring wheat. In the North and West regions of Paraná State, which are under subtropical conditions, harvest is in September and October. Those regions contribute to 60% of the overall country production. In South of Paraná and other states of Southern Brazil, namely Santa Catarina and Rio Grande do Sul, the harvest is in November. In all those regions, there are conditions conducive to PHS due to high temperatures and periodic rain. In 1996, the wheat cultivar Embrapa 16, which in just two years had covered 11.8% of wheat cultivated area in Paraná, was completely rejected for bread making because of PHS. In 1998, Embrapa 16 was sown on 1.5% of the total area of wheat in that State (Paraná, 1998)
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