Difference in volatile profile between pericarp tissue and locular gel in tomato fruit

Aroma, a complex mixture of volatile compounds, plays an important role in the perception and acceptability of tomato products by consumers. Numerous studies have reported volatile profiles in tomatoes based on measurement of the whole fruit or pericarp tissue, however, little is understood regarding the volatile compositions in the inner tissues. The objective of this study was to investigate the differences in volatile profile between pericarp tissue and locular gel in tomato fruit. Based on HS-SPME-GC-MS analysis, totally 42 volatile compounds were detected in FL 47 and Tasti-Lee tomato fruits. Regardless of cultivars, a substantial higher concentration of total volatile compounds was observed in pericarp than that in locular gel, associated with higher levels of aldehydes, hydrocarbons, and nitrogen compounds. Pericarp tissue possessed higher levels of cis-3-hexenal, hexanal, heptanal, octanal, nonanal, cymene, terpinolene, undecane, dodecane, 2-phenylethanol, 6-methyl-5-hepten-2-one, 2-methylbutyl acetate, 1-nitro-pentane, and 1-nitro-2-phenylethane, while the abundances of 2-methylpropanal, butanal, 2-methylbutanal, 2-methyl-2-butenal, 2-methylpropanol, 3-methylbutanol, 2-methylbutanol, and 2-butanone were higher in locular gel. Principal component analysis(PCA) and cluster analysis using GC-MS and electronic nose(E-nose) data discriminated the two tissues.

Comparative analysis of the transcriptomes of the calyx abscission zone of sweet orange insights into the huanglongbingassociated fruit abscission

Citrus greening disease or huanglongbing(HLB)is associated with excessive pre-harvest fruit drop.To understand the mechanisms of the HLB-associated fruit abscission,transcriptomes were analyzed by RNA sequencing of calyx abscission zones(AZ-C)of dropped“Hamlin”oranges from HLB-diseased trees upon shaking the trees(Dd),retained oranges on diseased trees(Rd),dropped oranges from healthy shaken trees(Dh),and retained oranges on healthy trees(Rh).Cluster analysis of transcripts indicated that Dd had the largest distances from all other groups.Comparisons of transcriptomes revealed 1047,1599,813,and 764 differentially expressed genes(DEGs)between Dd/Rd,Dd/Dh,Dh/Rh,and Rd/Rh.The gene ontology(GO)and Kyoto Encyclopedia of Genes and Genomes(KEGG)pathway enrichment analyses indicated hormone signaling,defense response,and secondary metabolism were involved in HLB-associated fruit abscission.Ethylene(ET)and jasmonic acid(JA)synthesis/signaling-related genes were upregulated in Dd,while other phytohormone-related genes were generally downregulated.In addition,genes related to JA/ET-activated defense response were upregulated in Dd as well.Consistent with the phytohormone gene expression data,increased levels(p<0.05)of ET and JA,and a decreased level(p<0.05)of abscisic acid were found in Dd compared with Rd,Dh or Rh.Lasiodiploidia theobromae level in Dd AZ-C was higher than the other fruit types,confirmed by qPCR,indicating AZ-C secondary fungal infection of HLB fruit may exacerbate their abscission.This information will help formulate effective strategies to control HLB-related abscission.

Beneficial horticultural responses from the application of solar thermotherapy to mature Huanglongbing-affected citrus trees

The detrimental effects of Huanglongbing(HLB)on citrus are well known and so is the need for effective methods to combat this disease.Solar thermotherapy(ST),one of the management methods to help alleviate some of the negative effects of HLB,is the process of heating trees to therapeutic temperatures by encompassing the tree within a plastic structure(Visqueen)to harness the sun’s natural energy.ST was applied to mature‘Valencia’citrus trees in three locations.Tree vigor,yield,and Candidatus Liberibacter asiaticus(Las)titer in leaves were monitored for two consecutive seasons post ST treatment,while fruit and juice quality were evaluated at the end of the second season.ST promoted an increase in canopy density in most groves tested and did not have a significant effect on fruit quantity,despite the prolonged exposure of the trees to increased temperatures.Moreover,Las titer was reduced in both leaves and juice processed from affected trees post ST.With respect to fruit quality,the ratio of total soluble solids to titratable acidity was higher post ST compared to controls as was the sucrose content of the juice in most treated groves,whereas limonin was higher in juice from control trees.Principal components analysis of aroma volatiles showed significant differences between juice from treated versus control trees with volatiles imparting top-note and freshness to orange juice,such as acetaldehyde,hexanal,Z-3-hexenol and linalool,being higher in juice fromtreated trees.Taste panels confirmed that flavor differences existed,ultimately showing that ST resulted in improved juice flavor in well-managed groves.Although the effects of ST on the trees appear temporary,such outcomes emphasize its utility when used as part of an integrated management strategy for HLB-affected citrus,imparting beneficial horticultural responses with minimal to positive effects on subsequent juice flavor.

Rationale for reconsidering current regulations restricting use of hybrids in orange juice

Huanglongbing(HLB)is a disease that has devastated the Florida citrus industry,threatens the entire U.S.citrus industry,and globally is rapidly spreading.Florida’s citrus production is 90%sweet orange,which is quite sensitive to HLB.The heavy reliance on sweet orange for Florida citrus production makes the industry especially vulnerable to diseases that are damaging to this type of citrus.Furthermore,90%of Florida oranges are used in producing orange juice that is defined by a federal regulation known as the“orange juice standard”,specifying that at least 90%of“orange juice”must be derived from Citrus sinensis.Genomic analyses definitively reveal that sweet orange is not a true species,but just one of many introgression hybrids of C.reticulata and C.maxima,with phenotypic diversity resulting from accumulated mutations in this single hybrid,the“sweet orange”.No other fruit industry is limited by law to such a narrow genetic base.Fortunately,there are new citrus hybrids displaying reduced sensitivity to HLB,and in some cases they produce juice,alone or in blends,that consumers would recognize as“orange juice”.Reconsidering current regulations on orange juice standards may permit use of such hybrids in“orange juice”,providing greater latitude for commercialization of these hybrids,leading to higher-quality orange juice and a more sustainable Florida orange juice industry.

Geochronology,Geochemistry,and Sr-Nd-Hf Isotopes of the Diorite Porphyrites from the Weining Beishan Area,Ningxia Hui Autonomous Region:Constraints on Their Source and Tectonic Implications

The Weining Beishan area of Ningxia Hui Autonomous Region is located at on the western edge of the Helanshan tectonic belt,which is a tectonic joint among Alxa Block,Ordos Block,and North Qilian orogenic belt.However,the tectonic evolution of this area remains unclear due to the lack of magmatic information.This paper conducted researches on geochronology,geochemistry,and Sr-Nd-Hf isotopes of the diorite porphyrites exposed in the Weining Beishan area.The zircon U-Pb dating yields two ages of 145.0±1.1 and 146.2±1.5 Ma,and the whole-rock geochemical data indicate that the diorite porphyrites are metaluminous to weakly peraluminous and high-K calc-alkaline series.The characteristics of highly initial^(87)Sr/^(86)Sr ratios(0.70816 to 0.71047),negativeε_(Nd)(t)(−8.9 to−8.4),and negativeε_(Hf)(t)(−13.8 to−21.2)indicate that the diorite porphyrites originated from partial melting of the middle-lower ancient crust related to the North China Craton.Combined with the regional geology,we suggested that partial melting was triggered by a tectonic activity of deep faults cutting through the crust under the regional stress transformation from compressing to extension during the Late Jurassic–Early Cretaceous,which is probably related to the westward subduction of the Paleo-Pacific Plate.