Genetic Variability and Elite Line Selection for High Essential Oil and Nepetalactone Content in Catmint (<i>Nepeta cataria</i>L.)

Nepeta cataria L., commonly known as catmint or catnip, belongs to the family “Lamiaceae” and is indigenous to Europe and Asia. The essential oil of this species is known for the richness and diversity of nepetalactones (NPL) which are used as mosquito/insect repellents in perfumery and cosmetic industries. Reports on Indian catmint germplasm are very meager and warrants exploration of its commercial potential as a natural, non-toxic source of insect repellents. With this objective, commercial open-pollinated seeds of catmint collected from its native, temperate habitat in Himalayas were introduced in the tropical plains. Subsequent to adaptation to a new zone we were able to isolate nineteen individual plants based on plant growth. Hydrodistillation of the fresh herb yielded essential oil in the range of 0.01% to 0.2%. Gas Chromatography (GC) and GC-Mass Spectrometry (GC-MS) analyses of the oil revealed the dominance of monoterpene hydrocarbon, namely, 4aα,7α,7aα NPL (1) isomer (84%). The other two isomers of nepetalactone, 4aα,7α,7aβ NPL (2) and 4aα,7β,7aα NPL (3) were also present, although in very less amounts (1.0% and 1.6%, respectively). Sesquiterpenes identified were α-humulene (traces), (E)-caryophyllene (0.6%) and caryophyllene oxide (1.7%). We compared the identified Indian catmint chemotype with the other oils from temperate, sub-tropical and tropical locations based on literature search. The Indian chemotype was found to be similar to the oils from Burundi, France, Turkey, UK and USA, mainly due to more accumulation of 4aα,7α,7aα NPL (1) isomer. These oils grouped together in Principal Component Analysis. Breeding lines are presently being developed to improve yield related traits in this plant. Multidisciplinary R&D efforts along with setting up industry related guidelines are required to successfully commercialize catmint cultivation. Several species of Nepeta genus have high nepetalactone content too and their potential as a commercial source of these isomers still needs to be explored.

Whole-genome resequencing of Cucurbita pepo morphotypes to discover genomic variants associated with morphology and horticulturally valuable traits

Cucurbita pepo contains two cultivated subspecies,each of which encompasses four fruit-shape morphotypes(cultivar groups).The Pumpkin,Vegetable Marrow,Cocozelle,and Zucchini Groups are of subsp.pepo and the Acorn,Crookneck,Scallop,and Straightneck Groups are of subsp.ovifera.Recently,a de novo assembly of the C.pepo subsp.pepo Zucchini genome was published,providing insights into its evolution.To expand our knowledge of evolutionary processes within C.pepo and to identify variants associated with particular morphotypes,we performed wholegenome resequencing of seven of these eight C.pepo morphotypes.We report for the first time whole-genome resequencing of the four subsp.pepo(Pumpkin,Vegetable Marrow,Cocozelle,green Zucchini,and yellow Zucchini)morphotypes and three of the subsp.ovifera(Acorn,Crookneck,and Scallop)morphotypes.A high-depth resequencing approach was followed,using the BGISEQ-500 platform that enables the identification of rare variants,with an average of 33.5X.Approximately 94.5%of the clean reads were mapped against the reference Zucchini genome.In total,3,823,977 high confidence single-nucleotide polymorphisms(SNPs)were identified.Within each accession,SNPs varied from 636,918 in green Zucchini to 2,656,513 in Crookneck,and were distributed homogeneously along the chromosomes.Clear differences between subspecies pepo and ovifera in genetic variation and linkage disequilibrium are highlighted.In fact,comparison between subspecies pepo and ovifera indicated 5710 genes(22.5%)with Fst>0.80 and 1059 genes(4.1%)with Fst=1.00 as potential candidate genes that were fixed during the independent evolution and domestication of the two subspecies.Linkage disequilibrium was greater in subsp.ovifera than in subsp.pepo,perhaps reflective of the earlier differentiation of morphotypes within subsp.ovifera.Some morphotype-specific genes have been localized.Our results offer new clues that may provide an improved understanding of the underlying genomic regions involved in the independent evolution and domestication of the two subspecies.Comparisons among SNPs unique to particular subspecies or morphotypes may provide candidate genes responsible for traits of high economic importance.

Assessment of Genetic Diversity of Moroccan Cultivated Almond(Prunus dulcis Mill.DA Webb)in Its Area of Extreme Diffusion,Using Nuclear Microsatellites

Assessment of genetic diversity of Moroccan cultivated almond (Prunus dulcis Mill.) grown from seed and cultivated at four eco-geographical regions was performed using 16 nuclear SSRs. 238 alleles were detected with an average of 14.88 alleles per locus, ranging from 4 (locus BPPCT027) to 24 (locus CPSCT018). The size of alleles ranged from 84 bp (locus UDP96-003) to 253 bp (locus UDP96-018). A high genetic diversity of the local almonds is apparent and structured into three major clusters (Oasis cluster, High and Anti Atlas cluster, and Middle Atlas cluster). Compared to the Mediterranean genetic pools, from the East to West, the genetic diversity tends to be limited in Morocco which is the area of its extreme diffusion.

Decoding altitude-activated regulatory mechanisms occurring during apple peel ripening

Apple(Malus domestica Borkh)is an important fruit crop cultivated in a broad range of environmental conditions.Apple fruit ripening is a physiological process,whose molecular regulatory network response to different environments is still not sufficiently investigated and this is particularly true of the peel tissue.In this study,the influence of environmental conditions associated with low(20 m)and high(750 m)altitude on peel tissue ripening was assessed by physiological measurements combined with metabolomic and proteomic analyses during apple fruit development and ripening.Although apple fruit ripening was itself not affected by the different environmental conditions,several key color parameters,such as redness and color index,were notably induced by high altitude.Consistent with this observation,increased levels of anthocyanin and other phenolic compounds,including cyanidin-3-O-galactoside,quercetin-3-O-rhamnoside,quercetin-3-O-rutinoside,and chlorogenic acid were identified in the peel of apple grown at high altitude.Moreover,the high-altitude environment was characterized by elevated abundance of various carbohydrates(e.g.,arabinose,xylose,and sucrose)but decreased levels of glutamic acid and several related proteins,such as glycine hydroxymethyltransferase and glutamate–glyoxylate aminotransferase.Other processes affected by high altitude were the TCA cycle,the synthesis of oxidative/defense enzymes,and the accumulation of photosynthetic proteins.From the obtained data we were able to construct a metabolite-protein network depicting the impact of altitude on peel ripening.The combined analyses presented here provide new insights into physiological processes linking apple peel ripening with the prevailing environmental conditions.

Whole genome re-sequencing of sweet cherry(Prunus avium L.)yields insights into genomic diversity of a fruit species

Sweet cherries,Prunus avium L.(Rosaceae),are gaining importance due to their perenniallity and nutritional attributes beneficial for human health.Interestingly,sweet cherry cultivars exhibit a wide range of phenotypic diversity in important agronomic traits,such as flowering time and defense reactions against pathogens.In this study,wholegenome resequencing(WGRS)was employed to characterize genetic variation,population structure and allelic variants in a panel of 20 sweet cherry and one wild cherry genotypes,embodying the majority of cultivated Greek germplasm and a representative of a local wild cherry elite phenotype.The 21 genotypes were sequenced in an average depth of coverage of 33.91×.and effective mapping depth,to the genomic reference sequence of‘Satonishiki’cultivar,between 22.21×to 36.62×.Discriminant analysis of principal components(DAPC)with SNPs revealed two clusters of genotypes.There was a rapid linkage disequilibrium decay,as the majority of SNP pairs with r2 in near complete disequilibrium(>0.8)were found at physical distances less than 10 kb.Functional analysis of the variants showed that the genomic ratio of non-synonymous/synonymous(dN/dS)changes was 1.78.The higher dN frequency in the Greek cohort of sweet cherry could be the result of artificial selection pressure imposed by breeding,in combination with the vegetative propagation of domesticated cultivars through grafting.The majority of SNPs with high impact(e.g.,stop codon gaining,frameshift),were identified in genes involved in flowering time,dormancy and defense reactions against pathogens,providing promising resources for future breeding programs.Our study has established the foundation for further large scale characterization of sweet cherry germplasm,enabling breeders to incorporate diverse germplasm and allelic variants to fine tune flowering and maturity time and disease resistance in sweet cherry cultivars.

Dormancy of Fig Cultivated under Moroccan Conditions

Fig (Ficus carica L.) is a deciduous species well adapted to Mediterranean conditions but its chilling requirement is still not well understood. The present study examines the pattern of bud-break in seven fig cultivars over two years under Moroccan conditions. Evaluation of dormancy behavior was made using a biological test known as “single node cuttings” carried out under controlled conditions. The responses of cultivars from Morocco, Italy, Spain and France were assessed. The period from full leaf fall to bud-break was characterized by a small variation (10 - 20 days) which did not appear to reflect the origin of the cultivars. Steady-sates were at high level in the middle of December or in January depending on the year. During the cold period, MTB didn’t exceed 200 days for “Borjassate noire”, “Ournakssi” and “Kadota” and varied from 100 to 128 days for the other cultivars. Therefore, dormancy was not deep and its period was short. Forcing bud during the coldest period allowed to a bud break but it didn’t exceed 10% and dormancy wasn’t complete. Missing bud break wasn’t observed and the geographic origin of examined cultivars didn’t seem to determine the length, and the deepness of bud dormancy. Bud-break occurred within a month of last leaf fall in the cultivars, indicating that they were all suited to commercial production in Morocco. Apparently, bud-break is more reliable in fig than it is in other Rosaceous species in this environment.