Inheritance of Rootstock Effects in Avocado (Persea americanaMill.) cv. Hass

Abstract

Grafting is typically utilized to merge adapted seedling rootstocks with highly productive clonal scions. This process implies the interaction of multiple genomes to produce a unique tree phenotype. Yet, the interconnection of both genotypes obscures individual contributions to phenotypic variation (i.e. rootstock-mediated heritability), hampering tree breeding. Therefore, our goal was to quantify the inheritance of seedling rootstock effects on scion traits using avocado (Persea americana Mill.) cv. Hass as model fruit tree. We characterized 240 rootstocks from 8 avocado cv. Hass orchards in three regions of the province of Antioquia, in the northwest Andes of Colombia, using 13 microsatellite markers (simple sequence repeats – SSRs). Parallel to this, we recorded 20 phenotypic traits (including morphological, eco-physiological, and fruit yield and quality traits) in the scions for three years (2015–2017). Relatedness among rootstocks was inferred through the genetic markers and inputted in a ‘genetic prediction’ model in order to calculate narrow-sense heritabilities (h2) on scion traits. We used three different randomization tests to highlight traits with consistently significant heritability estimates. This strategy allowed us to capture five traits with significant heritability values that ranged from 0.33 to 0.45 and model fits (R2) that oscillated between 0.58 and 0.74 across orchards. The results showed significance in the rootstock effects for four complex harvest and quality traits (i.e. total number of fruits, number of fruits with exportation quality, and number of fruits discarded because of low weight or thrips damage), while the only morphological trait that had a significant heritability value was overall trunk height (an emergent property of the rootstock-scion interaction). These findings suggest the inheritance of rootstock effects, beyond root phenotype, on a surprisingly wide spectrum of scion traits in ‘Hass’ avocado. They also reinforce the utility of SSR markers for relatedness reconstruction and genetic prediction of complex traits. This research is, up to date, the most cohesive evidence of narrow-sense inheritance of rootstock effects in a tropical fruit tree crop. Ultimately, our work reinforces the importance of considering the rootstock-scion interaction to broaden the genetic basis of fruit tree breeding programs, while enhancing our understanding of the consequences of grafting.

Allelic Diversity at Abiotic Stress Responsive Genes in Relationship to Ecological Drought Indices for Cultivated Tepary Bean, Phaseolus acutifolius A. Gray, and Its Wild Relatives

“…Phylogeographic inferences, e.g., [ 91 ] will also be improved by assuming independent gene mutation models [ 92 ], yet unlinked marker inferences are already available [ 93 , 94 , 95 ]. Finally, harnessing polygenic adaptive scores from gene-based and genome-wide prediction models [ 96 , 97 , 98 ] will help building a more cohesive picture of natural drought adaptation and vulnerability [ 99 ] in the face of climate change [ 100 ], with a focus on highly heterogeneous mountain geographies [ 101 ].…”

Fruit traits diversity in Burmese grape through multivariate analysis

“…Our study limitation was to discuss how fruit traits correlation may be due to a common genetic architecture or genetic hitchhiking (i.e., pleiotropy). It could be better described by linkage disequilibrium patterns or genetic covariance matrix (Arenas et al., 2021; Reyes‐Herrera et al., 2020). Our study deliberated genomic context‐dependent (i.e., epistatic) interactions and trade‐offs among the study fruit traits (Blair et al., 2016; Buitrago‐Bitar et al., 2021; Cortés & Blair, 2018; Cortés et al., 2013; Cortés et al., 2020; López‐Hernández & Cortés, 2019), but we were afraid not to do so.…”

Cacao parents help their offsprings to fight witches’ broom and black pod rot infections

“…The genetic materials chosen in the study were suitable for inducing precocity and resistance in susceptible cacao clones in commercial plantations, either as grafts or rootstocks. Previous research on cacao and other fruit trees has found heritability and the contribution of additive genetic effects (Reyes-Herrera et al 2020, Fernández-Paz et al 2021, Canas-Gutiérrez et al 2022. The selection allows new early tests for resistance to witches' broom and black pod rot, both in seedlings and nurseries, as a strategy to accelerate the reproductive age of plants.…”