Combinatory capacity and methylation profile in sweetpotato genotypes

Abstract

Sweet potato breeding programs need to constantly increase variability in the population and understand genetic processes to be successful. The use of diallels in sweet potatoes makes it possible to expand genetic variability and select superior genotypes for different abilities, while epigenetic studies, such as DNA methylation patterns, allow information on gene regulation and epigenetic inheritance to be obtained. These actions contribute to the success of a genetic improvement program. Thus, the objective of this research was to i) Estimate the ability to combine crosses between sweet potato clones and identify the best hybridizations for agronomic characteristics of interest; ii) Compare the DNA methylation patterns of two sweet potato cultivars maintained in greenhouse and tissue culture using methylation-sensitive amplification polymorphism analysis (MSAP). The study was divided into two chapters. In the first experiment, 378 full-sib genotypes of sweet potato were evaluated, coming from a partial diallel composed of 12 parents, including seven commercial cultivars and five pre-evaluated elite genotypes, which were also included as controls. The experimental design used was incomplete blocks, with two replications of the IC genotypes and twelve replications of each control. At 145 days after planting, data on branch productivity, productivity of total and commercial roots, unit weight of total and commercial roots, percentage of commercial roots, as well as the dry masses of roots and branches were collected. Statistical analysis was performed using linear mixed models, obtaining the predicted genotypic values, and also through diallel analysis, using the random method II model proposed by Grifing in 1956. Several genotypes were classified as promising. The genotypes that stood out most for general combining capacity were Brazlândia Roxa, Ligeirinha, UFLA-464, Uruguaiana with positive values for all characteristics. The specific cross between Amélia The second study was conducted in the United States at the Louisiana State University, where the DNA methylation patterns of two sweetpotato genotypes, Covington and Murasaki, were compared. These genotypes were grown under greenhouse and tissue culture conditions. MSAP analysis was performed to investigate the level of epigenetic variation. The methylation profiles of 36 cultivar accessions were identified, totaling 1096 loci analyzed. The results indicated that the methylation profileswere affected by both tissue culture and greenhouse. However, it was evident that tissue culture triggered a specific and consistent pattern of changes in methylation, which were more stable. Under greenhouse conditions, there was greater variability in methylation patterns between plants. Taken together, the verified results denote the importance of using diallel crosses and the quality of the propagative material in the sweetpotato improvement process. Therefore, the results obtained in the present studies contribute to the success of the sweetpotato breeding program.