Fruit quality and DNA methylation are affected by parental order in reciprocal crosses of tomato.

KEY MESSAGE: Reciprocal effects were found for tomato fruit quality and DNA methylation. The epigenetic identity of reciprocal hybrids indicates that DNA methylation might be one of the mechanisms involved in POEs. Crosses between different genotypes and even between different species are commonly used in plant breeding programs. Reciprocal hybrids are obtained by changing the cross direction (or the sexual role) of parental genotypes in a cross. Phenotypic differences between these hybrids constitute reciprocal effects (REs). The aim of this study was to evaluate phenotypic differences in tomato fruit traits and DNA methylation profiles in three inter- and intraspecific reciprocal crosses. REs were detected for 13 of the 16 fruit traits analyzed. The number of traits with REs was the lowest in the interspecific cross, whereas the highest was found in the cross between recombinant inbred lines (RILs) derived from the same interspecific cross. An extension of gene action analysis was proposed to incorporate parent-of-origin effects (POEs). Maternal and paternal dominance were found in four fruit traits. REs and paternal inheritance were found for epiloci located at coding and non-coding regions. The epigenetic identity displayed by the reciprocal hybrids accounts for the phenotypic differences among them, indicating that DNA methylation might be one of the mechanisms involved in POEs.

Selected genome regions for fruit weight and shelf life in tomato RILs discernible by markers based on genomic sequence information.

Fruit weight (FW) and shelf life (SL) are important traits in commercial fresh market tomatoes. A tomato RIL population was developed by antagonistic and divergent selection for both traits from an interspecific cross between the Solanum lycopersicum L. cv. "Caimanta" and the S. pimpinellifolium L. accession "LA0722". The objective of this work was to evaluate phenotypic and genetic components for FW and SL. Phenotypic data from RILs were collected during 3-year trials. Sixteen SSR, 62 InDels developed based on the genome sequences of "Caimanta" and "LA0722", and four functional markers for fruit size genes were used. FW and SL had a significant genetic variability, and both traits showed a genotype by year interaction. Genome-wide molecular characterization of the population demonstrated that is genetically structured according to FW. Marker data was used to study changes on allelic frequencies at loci between the phenotypic extreme group of RILs for FW and SL. Twenty four markers were associated to FW, the LC gene in chromosome 2 and other six markers in chromosomes 1, 2, 6, and 11 presented the most significant associations. Finally, we reported three new genomic regions located on chromosomes 9, 10 and 12 that underlie SL in tomato.

Assessment of genetic and epigenetic changes in virus-free garlic (Allium sativum L.) plants obtained by meristem culture followed by in vitro propagation.

KEY MESSAGE: This is the first report assessing epigenetic variation in garlic. High genetic and epigenetic polymorphism during in vitro culture was detected.Sequencing of MSAP fragments revealed homology with ESTs. Garlic (Allium sativum) is a worldwide crop of economic importance susceptible to viral infections that can cause significant yield losses. Meristem tissue culture is the most employed method to sanitize elite cultivars.Often the virus-free garlic plants obtained are multiplied in vitro (micro propagation). However, it was reported that micro-propagation frequently produces somaclonal variation at the phenotypic level, which is an undesirable trait when breeders are seeking to maintain varietal stability. We employed amplification fragment length polymorphism and methylation sensitive amplified polymorphism (MSAP) methodologies to assess genetic and epigenetic modifications in two culture systems: virus-free plants obtained by meristem culture followed by in vitro multiplication and field culture. Our results suggest that garlic exhibits genetic and epigenetic polymorphism under field growing conditions. However, during in vitro culture system both kinds of polymorphisms intensify indicating that this system induces somaclonal variation. Furthermore, while genetic changes accumulated along the time of in vitro culture, epigenetic polymorphism reached the major variation at 6 months and then stabilize, being demethylation and CG methylation the principal conversions.Cloning and sequencing differentially methylated MSAP fragments allowed us to identify coding and unknown sequences of A. sativum, including sequences belonging to LTR Gypsy retrotransposons. Together, our results highlight that main changes occur in the initial 6 months of micro propagation. For the best of our knowledge, this is the first report on epigenetic assessment in garlic.