In barley, three genes are responsible for the vernalization requirement: VrnH1, VrnH2 and VrnH3. The winter growth habit of barley requires the presence of a recessive VrnH1 allele, together with an active VrnH2 allele. The candidate for VrnH3 (HvFT1) has been recently identified, with evidences pointing at a central role in the integration of the vernalization and photoperiod pathways. Functional polymorphisms have been proposed, but experimental evidence of their role on agronomic performance and adaptation is needed. We examined allelic variation at the promoter and intron 1 of the HvFT1 gene in a landrace collection of barley, finding a high diversity level, with its geographic distribution correlated with latitude. Focusing on genotypes with winter alleles in VrnH1 and VrnH2, an association analysis of the four main HvFT1 haplotypes found in the landrace collection detected differences in time to flowering. Landraces with the intron 1 TC allele, prevalent in the south, flowered 6-7 days earlier than those with the AG allele, under natural conditions. These results were validated in an independent F(2) population. In both data sets, the effect found was similar, but in opposite direction to that described in literature. The polymorphism reported at intron 1 contributes to variation in flowering time under field conditions. We have found that polymorphisms at the promoter also contribute to the effect of the gene on flowering time under field and controlled conditions. The variety of HvFT1 alleles described constitutes an allelic series that may have been a factor in agro-ecological adaptation of barley.

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Saharan maize had been adapted to extreme conditions and could have developed resistance to different stresses. However, genebanks and breeding collections have poor representation from Saharan germplasm and, particularly, from Algeria. This is a preliminary approach to investigate the adaptation and agronomic performance of a representative sample of Saharan maize. We evaluated open-pollinated Saharan populations along with European and American cultivars during two years in humid and dry Spanish locations and in Algiers (Algeria). Saharan populations were able to grow in temperate environments, although results were not consistent over years and the genotype-by-environment interactions were very important. Some of the Algerian populations evaluated in 2010 showed promising yield and anthesissilking interval over environments, but none of the Algerian populations evaluated in 2009 were adequately adapted to Spanish conditions. These results suggest that there are wide ranges of variability within Saharan maize for adaptation to temperate conditions, and further evaluations of Saharan maize should identify potential base populations for breeding maize in either side of the Mediterranean Sea. However, this germplasm requires prebreeding for adaptation to temperate conditions in order to be adequate for breeding programs in temperate areas.

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Knowing the genetic regulation of fitness is crucial for using mutants in breeding programmes, particularly when the mutant is deleterious in some genetic backgrounds, as it happens with the sweet corn mutant sugary1 (su1) in maize (Zea mays L.). The fitness and genetic effects of maize mutant su1 were monitored through five successive selfing generations in two separated mean-generation designs. The first involved two inbreds with similar genetic backgrounds, while unrelated inbreds were used for the second design. Parents, F 1 s, F 2 s, and backcrosses were crossed to P39 as the donor of su1 and the 12 crosses were successively self-pollinated for 5 years. The su1 frequency decreased linearly across selfing generations in both designs. Additive effects were significant for su1 seed viability. However, dominance effects were of higher magnitude than additive effects, even though the dominance effects were not significant. Genetic effects depended on genotypes and environments. Therefore, the fitness of su1 is under genetic control, with significant additive effects due to minor contributions of multiple genes. The fitness of su1 is strongly affected by maize genotypic background and environment. It is hypothesized that genotypes could have evolutionary potential for modulating the fitness of single mutations.

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Sweet corn was originally due to the recessive allele sugary1 (su1). Sweet corn breeders frequently use field corn genotypes for broadening the narrow genetic base of sweet corn but they have to deal with the reduced viability of su1 plants within some field corn genetic backgrounds. Emergence and seedling vigor are the most critical traits affecting the viability of su1 plants. In two populations of RILs involving sweet corn inbred lines developed from B73×P39 and B73×IL14h, a net natural selection was revealed acting against the su1 allele. In the field, 27 QTLs were detected for the RILs released from B73P39 and 24 QTLs for those from B73IL14h, while different numbers of QTLs were detected in growth chamber trials, depending on the seed origin and evaluation conditions that were not consistent across genotypes or environments. The viability of su1 is under genetic and environmental controls with significant additive effects that are probably due to multiple genes with minor contribution. There are specific genes involved in the mutant viability and these genes depend not only on the mutant and the environment but also on the genetic background into which the mutant is introduced. Some of the QTLs identified in this study explained large proportions of variance and could be used by sweet corn breeders in breeding new genotypes from field × sweet corn crosses. These results suggest that there are specific mechanisms regulating the viability of the mutant by compensating for the deleterious effect of the defective mutant.

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