The almond [Prunus dulcis (Mill.) D.A. Webb] is normally self-sterile, requiring orchard placemen... more The almond [Prunus dulcis (Mill.) D.A. Webb] is normally self-sterile, requiring orchard placement of pollinizer cultivars and insect pollinators. Honeybees are the primary insect pollinators utilized, but climate change and the higher frequency of extreme weather events have reduced their availability to levels insufficient to meet the demands of current and anticipated almond acreage. The incorporation of self-fruitfulness may eliminate the need for both pollinizers and pollinators and allow the planting of single cultivar orchards that facilitate orchard management and reduce agrochemical inputs. Self-fruitfulness requires self-compatibility of self-pollen tube growth to fertilization, as well as a high level of consistent self-pollination or autogamy over the range of anticipated bloom environments. The Italian cultivar Tuono has been the sole source of self-compatibility for breeding programs world-wide, leading to high levels of inbreeding in current almond improvement program...
Aspergillus flavus Link. is a filamentous fungus affecting almond [Prunus dulcis (Mill.) D.A. Web... more Aspergillus flavus Link. is a filamentous fungus affecting almond [Prunus dulcis (Mill.) D.A. Webb] kernels in the field and during storage. This fungus can produce afla-toxins (carcinogenic and immunosuppressive mycotoxins), which prevent the marketability of almond kernels. Aspergillus flavus resistance has not been an objective in conventional almond breeding programs. Because the importance of this disease is increasing, evaluations of cultivar susceptibility are being performed. In this study, the screening for A. flavus resistance in 40 almond genotypes has been carried out in controlled inoculation conditions at 26 °C. Eighteen days after the inoculation, kernels of all the almond cultivars assayed showed susceptibility to A. flavus. Nevertheless, differences among cultivars in the percentage of kernel surface colonized by the fungus were observed. The Spanish cultivar Ramillette was the least susceptible. Susceptibility was not related to the geographic origin of the cultivar.
... Quantitative trait loci (QTL) controlling these traits have been localized on peach genome (P... more ... Quantitative trait loci (QTL) controlling these traits have been localized on peach genome (Peace et al., 2005a; 2006; Ogundiwin et al., 2007) using Pop-DG, a progeny population developed from crossing a non-melting cultivar 'Dr. Davis' to a fresh market cultivar Georgia Belle'. ...
Almond shell hardness is an economically important quality trait that protects the integrity of t... more Almond shell hardness is an economically important quality trait that protects the integrity of the kernel. It is directly related with shelling or crack-out percent. In the U.S. and Australian markets, soft to semi-hard shells varieties have been used in the industry, while in the European market, hard shells are dominantly sold and distributed. The origin of a hard shell is from wild almond species. Soft shells in the U.S. and Australia have been selected for a higher crack-out percent or larger kernel and ease of processing. Here we examined breeding populations totaling 264 trees that were genotyped with genotyping-by-sequencing (GBS) where shell hardness was measured with a texture analyzer, and shell weight, in-shell weights, and shell thickness were measured and crack-out percent was calculated. In a genome-wide association seven genetic loci were found to be associated with shell hardness, crack-out percent, shell thickness and shell weight. Of these seven, one was shared be...
Almond [Prunus dulcis (Mill.) D.A. Webb] is an economically important nut crop susceptible to the... more Almond [Prunus dulcis (Mill.) D.A. Webb] is an economically important nut crop susceptible to the genetic disorder, Non-infectious Bud Failure (NBF). Despite the severity of exhibition in several prominent almond cultivars, no causal mechanism has been identified underlying NBF development. The disorder is hypothesized to be associated with differential DNA methylation patterns based on patterns of inheritance (i.e., via sexual reproduction and clonal propagation) and previous work profiling methylation in affected trees. Peach (Prunus persica L. Batsch) is a closely related species that readily hybridizes with almond; however, peach is not known to exhibit NBF. A cross between an NBF-exhibiting ‘Carmel’ cultivar and early flowering peach (‘40A17’) produced an F1 where ∼50% of progeny showed signs of NBF, including canopy die-back, erratic branching patterns (known as “crazy-top”), and rough bark. In this study, whole-genome DNA methylation profiles were generated for three F1 proge...
First genetic linkage map of chilling injury susceptibility in peach (Prunus persica (L.) Batsch)... more First genetic linkage map of chilling injury susceptibility in peach (Prunus persica (L.) Batsch) fruit with SSR and SNP markers
While all organisms age, our understanding of how aging occurs varies among species. The aging pr... more While all organisms age, our understanding of how aging occurs varies among species. The aging process in perennial plants is not well-defined, yet can have implications on production and yield of valuable fruit and nut crops. Almond exhibits an age-related disorder known as non-infectious bud failure (BF) that affects vegetative bud development, indirectly affecting kernel yield. This species and disorder present an opportunity to address aging in a commercially relevant and vegetatively propagated perennial crop. The hypothesis tested in this study was that relative telomere length and/or telomerase reverse transcriptase (TERT) expression can serve as biomarkers of aging in almond. Relative telomere lengths and expression of TERT, a subunit of the enzyme telomerase, were measured via qPCR methods using bud and leaf samples collected from distinct age cohorts over a two-year period. Results from this work show a marginal but significant association between both relative telomere le...
While it is well known that all organisms age, our understanding of how aging occurs varies drama... more While it is well known that all organisms age, our understanding of how aging occurs varies dramatically among species. The aging process in perennial plants is not well defined, yet can have implications on production and yield of valuable fruit and nut crops. Almond, a relevant nut crop, exhibits an age-related disorder known as non-infectious bud failure (BF) that affects vegetative bud development, indirectly affecting kernel-yield. This species and disorder present an opportunity to address aging in a commercially-relevant and vegetatively-propagated, perennial crop threatened by an aging-related disorder. In this study, we tested the hypothesis that telomere length and/or TERT expression can serve as biomarkers of aging in almond using both whole-genome sequencing data and leaf samples collected from distinct age cohorts over a two-year period. To measure telomere lengths, we employed both in silico and molecular approaches. We also measured expression of TERT, a subunit of th...
Loss of genetic variability is an increasing challenge in tree breeding programs due to the repea... more Loss of genetic variability is an increasing challenge in tree breeding programs due to the repeated use of a reduced number of founder genotypes. However, in almond, little is known about the genetic variability in current breeding stocks, although several cases of inbreeding depression have been reported. To gain insights into the genetic structure in modern breeding programs worldwide, marker-verified pedigree data of 220 almond cultivars and breeding selections were analyzed. Inbreeding coefficients, pairwise relatedness, and genetic contribution were calculated for these genotypes. The results reveal two mainstream breeding lines based on three cultivars: “Tuono”, “Cristomorto”, and “Nonpareil”. Descendants from “Tuono” or “Cristomorto” number 76 (sharing 34 descendants), while “Nonpareil” has 71 descendants. The mean inbreeding coefficient of the analyzed genotypes was 0.041, with 14 genotypes presenting a high inbreeding coefficient, over 0.250. Breeding programs from France,...
Noninfectious bud-failure (BF) is a genetic disorder in almond, associated with nursery source se... more Noninfectious bud-failure (BF) is a genetic disorder in almond, associated with nursery source selection. Previously (Kester, PASHS, 1968), the latent potential for BF (BFpot) was shown to be heritable but its phenotypic expression (BFexp) varied among individual seedlings of a populations as a function of age. Vegetative propagation perpetuates BFpot of individual propagules (Kester and Asay, JASHS, 1978b) but the subsequent age of BFexp within individual plants is a function of accumulated exposure to high summer temperature and growth (Kester and Asay, JASHS 1978a). A recent 7-year “somatic heritability” study of 12 commercial nursery sources (Kester et al., HortScience 1998abst) portrays the total range of variability of BFpot and BFexp within the entire `Carmel' almond clonal population and includes a pattern of BF increase in consecutive vegetative propagation cycles that mimics patterns produced by phase change (i.e., juvenile > mature) phenomena (Hartmann et al., 1997...
The almond [Prunus dulcis (Mill.) D.A. Webb] is normally self-sterile, requiring orchard placemen... more The almond [Prunus dulcis (Mill.) D.A. Webb] is normally self-sterile, requiring orchard placement of pollinizer cultivars and insect pollinators. Honeybees are the primary insect pollinators utilized, but climate change and the higher frequency of extreme weather events have reduced their availability to levels insufficient to meet the demands of current and anticipated almond acreage. The incorporation of self-fruitfulness may eliminate the need for both pollinizers and pollinators and allow the planting of single cultivar orchards that facilitate orchard management and reduce agrochemical inputs. Self-fruitfulness requires self-compatibility of self-pollen tube growth to fertilization, as well as a high level of consistent self-pollination or autogamy over the range of anticipated bloom environments. The Italian cultivar Tuono has been the sole source of self-compatibility for breeding programs world-wide, leading to high levels of inbreeding in current almond improvement program...
Aspergillus flavus Link. is a filamentous fungus affecting almond [Prunus dulcis (Mill.) D.A. Web... more Aspergillus flavus Link. is a filamentous fungus affecting almond [Prunus dulcis (Mill.) D.A. Webb] kernels in the field and during storage. This fungus can produce afla-toxins (carcinogenic and immunosuppressive mycotoxins), which prevent the marketability of almond kernels. Aspergillus flavus resistance has not been an objective in conventional almond breeding programs. Because the importance of this disease is increasing, evaluations of cultivar susceptibility are being performed. In this study, the screening for A. flavus resistance in 40 almond genotypes has been carried out in controlled inoculation conditions at 26 °C. Eighteen days after the inoculation, kernels of all the almond cultivars assayed showed susceptibility to A. flavus. Nevertheless, differences among cultivars in the percentage of kernel surface colonized by the fungus were observed. The Spanish cultivar Ramillette was the least susceptible. Susceptibility was not related to the geographic origin of the cultivar.
... Quantitative trait loci (QTL) controlling these traits have been localized on peach genome (P... more ... Quantitative trait loci (QTL) controlling these traits have been localized on peach genome (Peace et al., 2005a; 2006; Ogundiwin et al., 2007) using Pop-DG, a progeny population developed from crossing a non-melting cultivar 'Dr. Davis' to a fresh market cultivar Georgia Belle'. ...
Almond shell hardness is an economically important quality trait that protects the integrity of t... more Almond shell hardness is an economically important quality trait that protects the integrity of the kernel. It is directly related with shelling or crack-out percent. In the U.S. and Australian markets, soft to semi-hard shells varieties have been used in the industry, while in the European market, hard shells are dominantly sold and distributed. The origin of a hard shell is from wild almond species. Soft shells in the U.S. and Australia have been selected for a higher crack-out percent or larger kernel and ease of processing. Here we examined breeding populations totaling 264 trees that were genotyped with genotyping-by-sequencing (GBS) where shell hardness was measured with a texture analyzer, and shell weight, in-shell weights, and shell thickness were measured and crack-out percent was calculated. In a genome-wide association seven genetic loci were found to be associated with shell hardness, crack-out percent, shell thickness and shell weight. Of these seven, one was shared be...
Almond [Prunus dulcis (Mill.) D.A. Webb] is an economically important nut crop susceptible to the... more Almond [Prunus dulcis (Mill.) D.A. Webb] is an economically important nut crop susceptible to the genetic disorder, Non-infectious Bud Failure (NBF). Despite the severity of exhibition in several prominent almond cultivars, no causal mechanism has been identified underlying NBF development. The disorder is hypothesized to be associated with differential DNA methylation patterns based on patterns of inheritance (i.e., via sexual reproduction and clonal propagation) and previous work profiling methylation in affected trees. Peach (Prunus persica L. Batsch) is a closely related species that readily hybridizes with almond; however, peach is not known to exhibit NBF. A cross between an NBF-exhibiting ‘Carmel’ cultivar and early flowering peach (‘40A17’) produced an F1 where ∼50% of progeny showed signs of NBF, including canopy die-back, erratic branching patterns (known as “crazy-top”), and rough bark. In this study, whole-genome DNA methylation profiles were generated for three F1 proge...
First genetic linkage map of chilling injury susceptibility in peach (Prunus persica (L.) Batsch)... more First genetic linkage map of chilling injury susceptibility in peach (Prunus persica (L.) Batsch) fruit with SSR and SNP markers
While all organisms age, our understanding of how aging occurs varies among species. The aging pr... more While all organisms age, our understanding of how aging occurs varies among species. The aging process in perennial plants is not well-defined, yet can have implications on production and yield of valuable fruit and nut crops. Almond exhibits an age-related disorder known as non-infectious bud failure (BF) that affects vegetative bud development, indirectly affecting kernel yield. This species and disorder present an opportunity to address aging in a commercially relevant and vegetatively propagated perennial crop. The hypothesis tested in this study was that relative telomere length and/or telomerase reverse transcriptase (TERT) expression can serve as biomarkers of aging in almond. Relative telomere lengths and expression of TERT, a subunit of the enzyme telomerase, were measured via qPCR methods using bud and leaf samples collected from distinct age cohorts over a two-year period. Results from this work show a marginal but significant association between both relative telomere le...
While it is well known that all organisms age, our understanding of how aging occurs varies drama... more While it is well known that all organisms age, our understanding of how aging occurs varies dramatically among species. The aging process in perennial plants is not well defined, yet can have implications on production and yield of valuable fruit and nut crops. Almond, a relevant nut crop, exhibits an age-related disorder known as non-infectious bud failure (BF) that affects vegetative bud development, indirectly affecting kernel-yield. This species and disorder present an opportunity to address aging in a commercially-relevant and vegetatively-propagated, perennial crop threatened by an aging-related disorder. In this study, we tested the hypothesis that telomere length and/or TERT expression can serve as biomarkers of aging in almond using both whole-genome sequencing data and leaf samples collected from distinct age cohorts over a two-year period. To measure telomere lengths, we employed both in silico and molecular approaches. We also measured expression of TERT, a subunit of th...
Loss of genetic variability is an increasing challenge in tree breeding programs due to the repea... more Loss of genetic variability is an increasing challenge in tree breeding programs due to the repeated use of a reduced number of founder genotypes. However, in almond, little is known about the genetic variability in current breeding stocks, although several cases of inbreeding depression have been reported. To gain insights into the genetic structure in modern breeding programs worldwide, marker-verified pedigree data of 220 almond cultivars and breeding selections were analyzed. Inbreeding coefficients, pairwise relatedness, and genetic contribution were calculated for these genotypes. The results reveal two mainstream breeding lines based on three cultivars: “Tuono”, “Cristomorto”, and “Nonpareil”. Descendants from “Tuono” or “Cristomorto” number 76 (sharing 34 descendants), while “Nonpareil” has 71 descendants. The mean inbreeding coefficient of the analyzed genotypes was 0.041, with 14 genotypes presenting a high inbreeding coefficient, over 0.250. Breeding programs from France,...
Noninfectious bud-failure (BF) is a genetic disorder in almond, associated with nursery source se... more Noninfectious bud-failure (BF) is a genetic disorder in almond, associated with nursery source selection. Previously (Kester, PASHS, 1968), the latent potential for BF (BFpot) was shown to be heritable but its phenotypic expression (BFexp) varied among individual seedlings of a populations as a function of age. Vegetative propagation perpetuates BFpot of individual propagules (Kester and Asay, JASHS, 1978b) but the subsequent age of BFexp within individual plants is a function of accumulated exposure to high summer temperature and growth (Kester and Asay, JASHS 1978a). A recent 7-year “somatic heritability” study of 12 commercial nursery sources (Kester et al., HortScience 1998abst) portrays the total range of variability of BFpot and BFexp within the entire `Carmel' almond clonal population and includes a pattern of BF increase in consecutive vegetative propagation cycles that mimics patterns produced by phase change (i.e., juvenile > mature) phenomena (Hartmann et al., 1997...
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