Association mapping in multiple yam species (Dioscorea spp.) of quantitative trait loci for yield-related traits.

BACKGROUND: Yam (Dioscorea spp.) is multiple species with various ploidy level and considered as cash crop in many producing areas. Selection based phenotyping for yield and its related traits such as mosaic virus and anthracnose diseases resistance and plant vigor in multiple species of yam is lengthy however, marker information has proven to enhance selection efficiency. METHODOLOGY: In this study, a panel of 182 yam accessions distributed across six yam species were assessed for diversity and marker-traits association study using SNP markers generated from Diversity Array Technology platform. For the traits association analysis, the relation matrix alongside the population structure were used as co-factor to avoid false discovery using Multiple random Mixed Linear Model (MrMLM) followed by gene annotation. RESULTS: Accessions performance were significantly different (p < 0.001) across all the traits with high broad-sense heritability (H2). Phenotypic and genotypic correlations showed positive relationships between yield and vigor but negative for yield and yam mosaic disease severity. Population structure revealed k = 6 as optimal clusters-based species. A total of 22 SNP markers were identified to be associated with yield, vigor, mosaic and anthracnose diseases resistance. Gene annotation for the significant SNP loci identified some putative genes associated with primary metabolism, pest and resistance to anthracnose disease, maintenance of NADPH in biosynthetic reaction especially those involving nitro-oxidative stress for resistance to mosaic virus, and seed development, photosynthesis, nutrition use efficiency, stress tolerance, vegetative and reproductive development for tuber yield. CONCLUSION: This study provides valuable insights into the genetic control of plant vigor, anthracnose, mosaic virus resistance, and tuber yield in yam and thus, opens an avenue for developing additional genomic resources for markers-assisted selection focusing on multiple yam species.

Effects of prenatal and lactation nicotine exposure on rat testicular interstitial tissue.

Nicotine is largely consumed as a component of cigarettes. It induces apoptosis, interferes with endocrine function by changing the sex hormones secretion and leads to male infertility. Testosterone is produced from cholesterol by Leydig cells (LC), with the participation of testicular macrophages (MO). Thus, to investigate whether nicotine administration to pregnant and lactating rats changes cholesterol and sexual hormone levels and LC and MO populations of offspring, female rats received nicotine (2 mg/kg/day) through osmotic minipumps from the first day of pregnancy up to the end of weaning. At 1, 30, 60 and 90 days post-partum (dpp) the plasma cholesterol and testosterone levels were obtained, as well as the biometric, histopathological and stereological testicular parameters. Nicotine reduced the body weight, cholesterol levels and lipid droplet number in foetal LC at 1 dpp. The number of apoptotic LC did not change in the offspring of nicotine group at any age studied. No alterations in the numerical densities of MO and LC occurred at 60 and 90 dpp. Hypertrophy of mature LC and increase in cholesterol and testosterone levels were noted at 90 dpp. In conclusion, nicotine when administered to rats throughout pregnancy and lactation induces morphofunctional alterations of foetal and mature LC and affects cholesterol and testosterone levels.