Heritability of adventitious rooting of grapevine dormant canes

First online: 30 October 2012One of the most important viticultural characteristics of a grapevine rootstock is the ability to form roots on dormant lignified canes (rootstrike). North American species of Vitis are the primary source of germplasm for grapevine rootstocks and vary widely in their rate of rootstrike. Breeders have hybridized grape species in order to introgress traits to produce commercial rootstocks. A combination of 26 parents consisting of improved and wild accessions of Vitis spp. was used to generate 27 families. The percentage of rootstrike of dormant canes was observed over several years for 552 individuals. A logistic generalized linear mixed model (GLMM) method was used to estimate the narrow sense heritability (h 2) of rootstrike. Heritability was found to be moderate (h 2 = 0.307 ± 0.050). The model also estimated breeding values of all parents and progeny. A GLMM method can be used to estimate breeding values of germplasm to identify individuals with commercially acceptable rates of rootstrike with a defined probability of transmitting this trait to progeny. This is useful for the introgression of traits into potentially new commercial rootstocks. The pattern of normal distribution of rooting indicates that it is possible to identify individuals with good rootstrike from Vitis species that are generally considered to have low rootstrike. Selection of individuals with a higher breeding value will increase the efficiency of rootstock breeding.Brady P. Smith, Matthew S. Wheal, Tim H. Jones, Norma B. Morales and Peter R. Clingeleffe

Resilience Among Older Adolescents in Foster Care: the Impact of Risk and Protective Factors

This study explores the phenomenon of resilience among older adolescents in foster care. Data from 351 youths approaching the age of emancipation were examined. Resilience was measured by a composite score combining six domains: educational attainment, and avoidance of teen pregnancy, homelessness, mental illness, substance use and criminal involvement. Increased physical abuse, a history of sexual abuse, placement instability and delinquency in youths’ original families were associated with lower resilience. Non-white race was associated with higher resilience even after risk and protective factors were controlled. These findings highlight factors that contribute to resilient functioning and may be targeted for interventions promoting competence among these high-risk youth