Transferable DNA markers are essential for breeding and genetics. Grapevine (Vitis) breeders utilize disease resistance alleles from congeneric species~20 million years divergent, but existing Vitis marker platforms have cross-species transfer rates as low as 2%. Here, we apply a marker strategy targeting the inferred Vitis core genome. Incorporating seven linkedread de novo assemblies and three existing assemblies, the Vitis collinear core genome is estimated to converge at 39.8 Mb (8.67% of the genome). Adding shotgun genome sequences from 40 accessions enables identification of conserved core PCR primer binding sites flanking polymorphic haplotypes with high information content. From these target regions, we develop 2,000 rhAmpSeq markers as a PCR multiplex and validate the panel in four biparental populations spanning the diversity of the Vitis genus, showing transferability increases to 91.9%. This marker development strategy should be widely applicable for genetic studies in many taxa, particularly those~20 million years divergent.

Race-specific resistance loci, whether having qualitative or quantitative effects, present plant-breeding challenges for phenotypic selection and deciding which loci to select or stack with other resistance loci for improved durability. Previously, resistance to grapevine powdery mildew (GPM, caused by Erysiphe necator) was predicted to be conferred by at least three race-specific loci in the mapping family B37-28 × C56-11 segregating for GPM resistance from Vitis aestivalis. In this study, 9 years of vineyard GPM disease severity ratings plus a greenhouse and laboratory assays were genetically mapped, using a rhAmpSeq core genome marker platform with 2,000 local haplotype markers. A new qualitative resistance locus, named REN11, on the chromosome (Chr) 15 was found to be effective in nearly all (11 of 12) vineyard environments on leaves, rachis, berries, and most of the time (7 of 12) stems. REN11 was independently validated in a pseudo-testcross with the grandparent source of resistance, “Tamiami.” Five other loci significantly predicted GPM severity on leaves in only one or two environments, which could indicate race-specific resistance or their roles in different timepoints in epidemic progress. Loci on Chr 8 and 9 reproducibly predicted disease severity on stems but not on other tissues and had additive effects with REN11 on the stems. The rhAmpSeq local haplotype sequences published in this study for REN11 and Chr 8 and 9 stem quantitative trait locus (QTL) can be used directly for marker-assisted selection or converted to SNP assays. In screening for REN11 in a diversity panel of 20,651 vines representing the diversity of Vitis, this rhAmpSeq haplotype had a false positive rate of 0.034% or less. The effects of the other foliar resistance loci detected in this study seem too unstable for genetic improvement regardless of quantitative effect size, whether due to race specificity or other environmental variables.

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: Optimum fruit quality depends upon a number of factors, including fruit developmental stage at harvest. The volatile constituents present in apricot fruit and plumcot accession P251-002 during three di †erent developmental stages have been studied, as well as some physical characteristics such as weight, Ðrm-ness, ¡Brix, titratable acidity and Ñesh and skin colour. The volatile compounds behaved di †erently during the fruit maturation period, alcohols being the most important group, quantitatively, during the three developmental stages in apricot fruit. In plumcot, total volatiles obtained from fruit sample extractions were very similar in each developmental stage ; however, the aromatic proÐle of constituents changed as fruit maturity progressed to a tree ripe stage. Important di †er-ences were found in the volatile constituents proÐle for both fruits ; at the tree ripe stage, the concentration of lactones and terpenic alcohols, characteristic compounds of apricot aroma, were much higher in apricot than plumcot, the latter more resembling a plum aromatic proÐle. Even with the important presence of lactones that gives a very aromatic apricot when tree ripe, the low Ðrm-ness at this point does not allow any commercial use of the fruit.

Apricot is in the Rosaceae family within the genus Prunus L., subgenus Prunophora Focke, and the section Armeniaca (Lam.) Koch. Depending on the classifi cation system, the number of apricot species ranges from 3 to 12. Six distinct species are usually recognized: P . brigantina Vill., P . holosericeae Batal, P . armeniaca L., P . mandshurica (Maxim), P . sibirica L., Japanese apricot P . mume (Sieb.) Sieb. & Succ. Vavilov placed apricot in three centers of origin: the Chinese center (Central and Western China), the Central Asiatic center (Afghanistan, northwest India and Pakistan, Kashmir, Tajikistan, Uzbekistan, Xinjing province in China and western Tien-Shan), and the Near-Eastern center (interior of Asia Minor). Kostina further divided the cultivated apricot according to their adaptability into four major ecogeographical groups : (1) the Central Asian group, (2) the Iran-Caucasian group, (3) the European group, and (4) the Dzhungar-Zailij group. Many local cultivars are grown in the different areas and producing countries; however, these cultivars lack important traits that needed by modern production and marketing systems. Breeding programs have and continue to develop cultivars with improved adaptability to the environment (temperature requirements, water defi cit), extension of the harvest season, fruit quality for fresh consumption and processing, productivity, adequate tree size, and resistance to biotic stresses. The major objectives in apricot breeding

Central Asian apricot germplasm was used in hybridizations with California adapted apricots to increase Brix levels and improve fresh eating quality. Fruit from parental trees, the F 1 hybrid and two backcross families were evaluated for fruit quality traits and analyzed by HPLC for specific sugar content. The F 1 hybrid between Central Asian and California adapted apricots was intermediate to its parents in many of the evaluated characteristics and levels of specific sugars. When the F 1 hybrid was backcrossed to California adapted apricots 'Lorna' and 'Robada,' the resulting hybrids were diverse in Brix, juice acidity, fruit size and profiles of specific sugars. Glucose: fructose ratios higher that 3.3 were encountered in fruit from five of the 22 analyzed seedlings, and fructose: sorbitol ratio ranged from 0.67 to 6.46. Brix and total sugar content correlated significantly with each other and with both sucrose and glucose. No significant correlations existed between sorbitol and any of the other analyzed sugars, nor with Brix or total sugars. The results demonstrated the extent of sugar profile modification possible in California adapted apricots after just two generations of breeding with Central Asian apricot germplasm.

A series of laboratory and field studies were conducted using three lines of navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), reared on wheat bran diet and almonds, Prunus dulcis (Mill.) D.A.Webb, at constant and fluctuating temperature. The duration of development on wheat bran diet at constant temperature differed significantly among the three lines. Development was as much as 40% faster at constant temperature than at fluctuating temperatures, consequently the developmental duration determined at constant temperature was not an absolute measure. When the maximum temperature in fluctuating regimes exceeded 43 degrees C, survival decreased by 50% compared with the constant temperature control. In almonds held at constant temperature, the developmental rate on new-crop nuts was variety-dependent and was fastest on 'Nonpareil' almonds and slowest on the experimental selection '23-122'. Development and survival were also variety-dependent on unharvested (mummy) almonds, and navel orangeworm average emergence was earliest from Nonpareil and latest from 'Carmel' nuts, differing by 529 degree-days, whereas survival was the highest on 'Butte', 35.7%, and the lowest on Carmel nuts, 7.2%. In our trials, both the speed of development and survival depended on host age, variety and quality, indicating that almonds were a dynamic rather than a static nutrient source for navel orangeworm. Identifying the factors responsible for variation in development and survival will give insight into improving control strategies.