Color and pigment contents are important aspects of fruit quality and consumer acceptance of cucurbit crops. Here, we describe the independent mapping and cloning of a common causative APRR2 gene regulating pigment accumulation in melon and watermelon. We initially show that the APRR2 transcription factor is causative for the qualitative difference between dark and light green rind in both crops. Further analyses establish the link between sequence or expression level variations in the CmAPRR2 gene and pigment content in the rind and flesh of mature melon fruits. A genome-wide association study (GWAS) of young fruit rind color in a panel composed of 177 diverse melon accessions did not result in any significant association, leading to an earlier assumption that multiple genes are involved in shaping the overall phenotypic variation in this trait. Through resequencing of 25 representative accessions and allelism tests between light rind accessions, we show that multiple independent single nucleotide polymorphisms in the CmAPRR2 gene are causative of the light rind phenotype. The multi-haplotypic nature of this gene explains the lack of detection power obtained through genotyping by sequencing-based GWAS and confirms the pivotal role of this gene in shaping fruit color variation in melon. This study demonstrates the power of combining bi- and multi-allelic designs with deep sequencing, to resolve lack of power due to high haplotypic diversity and low allele frequencies. Due to its central role and broad effect on pigment accumulation in fruits, the APRR2 gene is an attractive target for carotenoid bio-fortification of cucurbit crops.

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The aim to the study was to determine the physicochemical composition, bioactive compounds and antioxidant activity of fruits from Yucatan, Mexico such as star apple, cashew, mombin, mamey sapote, white sapote, sugar apple, sapodilla, dragon fruit, nance, ilama, custard apple, mamoncillo and black sapote. The physicochemical characteristics were different between fruits and were good sources of bioactive compounds. The edible part with the highest values of antioxidant activity were mamoncillo, star apple, mombin, cashew, white sapote, ilama, custard apple, sugar apple, and nance. Total soluble phenols content showed a correlation with antioxidant activity by ABTS (R=0.52, P⩽0.05) and DPPH (R=0.43, P⩽0.05). A high correlation was obtained between the two assays (ABTS and DPPH) used to measure antioxidant activity in the tropical fruit species under study (R=0.82, P⩽0.05). The results show promising perspectives for the exploitation and use of tropical fruits studied with significant levels of nutrients and antioxidant activity.

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Twenty-four exotic Colombian fruits were evaluated for antioxidant activity and total soluble phenolics (TP) (edible part, seed and peel) and ascorbic acid content (edible part). The antioxidant activities were evaluated by ABTS (free radical-scavenging capacity) and FRAP (ferric reducing antioxidant power) methods. The ABTS, FRAP, TP and ascorbic acid values in the edible part were 3.25 to 175μM Trolox equiv/g fresh weight (FW), 6.29 to 144μM Trolox equiv/g FW, 15.7 to 1018mg gallic acid equiv/100g FW, and 0.53 to 257mg ascorbic acid/100g FW respectively. There were positive correlations between antioxidant activity (assessed by both ABTS and FRAP) and TP and ascorbic acid with the FRAP and ABTS methods. The edible part of banana passion fruits (P. tarminiana and P. mollisima) exhibited the highest values of antioxidant activity and total phenolics, while the highest level of ascorbic acid was recorded in the edible part of guava apple and cashew. The seeds with the highest values of antioxidant activity and total phenols were cashew, algarrobo, arazá and coastal sapote, while the peel of coastal sapote and algarrobo had the highest values of antioxidant activity and total phenolics. To the best of our knowledge, this paper reports the first evaluation of pulp, seed and skin of Colombian tropical fruits with a view to their knowledge utilization for the development of novel functional food products.

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Background The control of plant anthocyanin accumulation is via transcriptional regulation of the genes encoding the biosynthetic enzymes. A key activator appears to be an R2R3 MYB transcription factor. In apple fruit, skin anthocyanin levels are controlled by a gene called MYBA or MYB1, while the gene determining fruit flesh and foliage anthocyanin has been termed MYB10. In order to further understand tissue-specific anthocyanin regulation we have isolated orthologous MYB genes from all the commercially important rosaceous species. Results We use gene specific primers to show that the three MYB activators of apple anthocyanin (MYB10/MYB1/MYBA) are likely alleles of each other. MYB transcription factors, with high sequence identity to the apple gene were isolated from across the rosaceous family (e.g. apples, pears, plums, cherries, peaches, raspberries, rose, strawberry). Key identifying amino acid residues were found in both the DNA-binding and C-terminal domains of these MYBs. The expression of these MYB10 genes correlates with fruit and flower anthocyanin levels. Their function was tested in tobacco and strawberry. In tobacco, these MYBs were shown to induce the anthocyanin pathway when co-expressed with bHLHs, while over-expression of strawberry and apple genes in the crop of origin elevates anthocyanins. Conclusions This family-wide study of rosaceous R2R3 MYBs provides insight into the evolution of this plant trait. It has implications for the development of new coloured fruit and flowers, as well as aiding the understanding of temporal-spatial colour change.

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Background and aims Ethnobotanical studies in Mexico have documented that Mesoamerican peoples practise systems of in situ management of wild and weedy vegetation directed to control availability of useful plants. In situ management includes let standing, encouraging growing and protection of individual plants of useful species during clearance of vegetation, which in some cases may involve artificial selection. The aim of this study was to review, complement and re-analyse information from three case studies which examined patterns of morphological, physiological and genetic effects of artificial selection in plant populations under in situ management in the region. Methods Information on wild and in situ managed populations of the herbaceous weedy plants Anoda cristata and Crotalaria pumila, the tree Leucaena esculenta subsp. esculenta and the columnar cacti Escontria chiotilla, Polaskia chichipe and Stenocereus stellatus from Central Mexico was re-analysed. Analyses compared morphology and frequency of morphological variants, germination patterns, and population genetics parameters between wild and managed in situ populations of the species studied. Species of columnar cacti are under different management intensities and their populations, including cultivated stands of P. chichipe and S. stellatus, were also compared between species. Key results Significant differences in morphology, germination patterns and genetic variation documented between wild, in situ managed and cultivated populations of the species studied are associated with higher frequencies of phenotypes favoured by humans in managed populations. Genetic diversity in managed populations of E. chiotilla and P. chichipe is slightly lower than in wild populations but in managed populations of S. stellatus variation was higher than in the wild. However, genetic distance between populations was generally small and influenced more by geographic distance than by management. Conclusions Artificial selection operating on in situ managed populations of the species analysed is causing incipient domestication. This process could be acting on any of the 600-700 plant species documented to be under in situ management in Mesoamerica. In situ domestication of plants could be relevant to understand early processes of domestication and current conditions of in situ conservation of plant genetic resources.

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