Linkage disequilibrium in Brazilian Santa Inês breed, \u3ci\u3eOvis aries\u3c/i\u3e

For genomic selection to be successful, there must be sufficient linkage disequilibrium between the markers and the causal mutations. The objectives of this study were to evaluate the extent of LD in ovine using the Santa Inês breed and to infer the minimum number of markers required to reach reasonable prediction accuracy. In total, 38,168 SNPs and 395 samples were used. The mean LD between adjacent marker pairs measured by r2 and |D′| were 0.166 and 0.617, respectively. LD values between adjacent marker pairs ranged from 0.135 to 0.194 and from 0.568 to 0.650 for r2 for |D′| across all chromosomes. The average r2 between all pairwise SNPs on each chromosome was 0.018. SNPs separated by between 0.10 to 0.20 Mb had an estimated average r2 equal to 0.1033. The identified haplotype blocks consisted of 2 to 21 markers. Moreover, estimates of average coefficients of inbreeding and effective population size were 0.04 and 96, respectively. LD estimated in this study was lower than that reported in other species and was characterized by short haplotype blocks. Our results suggest that the use of a higher density SNP panel is recommended for the implementation of genomic selection in the Santa Inês breed

Large variability in drought survival among <em>Urochloa</em> spp. cultivars

International audienceThe Urochloa spp. cultivars are largely used for forage production in tropical and humid subtropical zones in Brazil. However, in areas of transition to drier zones, the persistence of Urochloa cultivars may be jeopardized by severe drought. We aimed to quantify and describe variability in growth potential under irrigation as well as dehydration tolerance and avoidance in cultivars under severe drought of Urochloa C4 species (Urochloa brizantha, cvs. Marandu and BRS Paiaguás and Urochloa decumbens cv. Basilisk), which were hypothesized to be less dehydration tolerant than a Mediterranean C3 species (Dactylis glomerata L. cv. Medly). Two experiments were carried out in a controlled environment—one in pots and one in long tubes—each under irrigation and drought successively. Marandu and Basilisk cultivars produced double the aerial and root biomass of cv. BRS Paiaguás. Their root systems were also deeper conferring them higher dehydration avoidance; however, they exhibited lower dehydration tolerance under severe drought. Conversely, cv. BRS Paiaguás was less productive, more dehydration tolerant and, therefore, able to survive at lower soil moisture, similar to the drought tolerant cv. Medly. The BRS Paiaguás cultivar may show sward persistence where extreme drought is experienced, but results should be confirmed under field conditions

Linkage disequilibrium in Brazilian Santa Inês breed, \u3ci\u3eOvis aries\u3c/i\u3e

For genomic selection to be successful, there must be sufficient linkage disequilibrium between the markers and the causal mutations. The objectives of this study were to evaluate the extent of LD in ovine using the Santa Inês breed and to infer the minimum number of markers required to reach reasonable prediction accuracy. In total, 38,168 SNPs and 395 samples were used. The mean LD between adjacent marker pairs measured by r2 and |D′| were 0.166 and 0.617, respectively. LD values between adjacent marker pairs ranged from 0.135 to 0.194 and from 0.568 to 0.650 for r2 for |D′| across all chromosomes. The average r2 between all pairwise SNPs on each chromosome was 0.018. SNPs separated by between 0.10 to 0.20 Mb had an estimated average r2 equal to 0.1033. The identified haplotype blocks consisted of 2 to 21 markers. Moreover, estimates of average coefficients of inbreeding and effective population size were 0.04 and 96, respectively. LD estimated in this study was lower than that reported in other species and was characterized by short haplotype blocks. Our results suggest that the use of a higher density SNP panel is recommended for the implementation of genomic selection in the Santa Inês breed