Genomic data is a powerful tool. However, the phylogenetic relationships among different ecological races of avocado remain unclear. Here, we used the results from specific length amplified fragment sequencing (SLAF-seq) and transcriptome data to infer the population structure and genetic diversity of 21 avocado cultivars and reconstructed the phylogeny of three ecological races and two interracial hybrids. The results of the three analyses performed (unweighted pair-group methods with arithmetic means (UPGMA) cluster, Principal coordinate analysis (PCoA), and STRUCTURE) based on single nucleotide polymorphisms (SNPs) from SLAF-seq all indicated the existence of two populations based on botanical race: Mexican–Guatemalan and West Indian genotype populations. Our results based on SNPs from SLAF-seq indicated that the Mexican and Guatemalan races were more closely related to each other than either was to the West Indian race, which also was confirmed in the UPGMA cluster results based on SNPs from transcriptomic data. SNPs from SLAF-seq provided strong evidence that the Guatemalan, Mexican, and Guatemalan × Mexican hybrid accession possessed higher genetic diversity than the West Indian races and Guatemalan × West Indian hybrid accessions. Six race-specific Kompetitive allele specific PCR (KASP) markers based on SNPs from SLAF-seq were then developed and validated.
In mainland China, the most popular pineapple cultivar is 'Comte de Paris'. Gibberellic acids have been widely applied to enhance fruit growth in various species. To evaluate the effect of gibberellic acid (GA 3 ) on 'Comte de Paris' pineapple production and quality, pineapple fruits were sprayed with GA 3 at concentrations of 5, 20, 50, or 100 mg l -1 at both 0 and 15 days after flowering (DAF). Fruits were sampled every 15 days from 0 to 60 DAF (maturation) for flow cytometric analysis and histological observation. The results showed that the treatments with the three highest concentrations of GA 3 significantly increased fruit weight, and the most effective concentration was 50 mg l -1 GA 3 , which increased the flesh weight by 20.3% compared to the control. Although treatment with GA 3 had little effect on the total soluble solids and fruit juice pH, it increased the vitamin C content. Although flow cytometric analysis showed that the 50 mg l -1 GA 3 treatment had only a slight impact on the number of S phase cells, histological observations indicated that the increase of fruit volume and flesh weight under this GA 3 treatment was not due to the increase of cell number but a result of the increase of cell area in the fruit flesh.
Avocado (Persea americana Mill.) could be considered as an important tropical and subtropical woody oil crop with high economic and nutritional value. Despite the importance of this species, genomic information is currently unavailable for avocado and closely related congeners. In this study, we generated more than 216 million clean reads from different avocado ecotypes using Illumina HiSeq high-throughput sequencing technology. The high-quality reads were assembled into 154,310 unigenes with an average length of 922 bp. A total of 55,558 simple sequence repeat (SSR) loci detected among the 43,270 SSR-containing unigene sequences were used to develop 74,580 expressed sequence tag (EST)-SSR markers. From these markers, a subset of 100 EST-SSR markers was randomly chosen to identify polymorphic EST-SSR markers in 28 avocado accessions. Sixteen EST-SSR markers with moderate to high polymorphism levels were detected, with polymorphism information contents ranging from 0.33 to 0.84 and averaging 0.63. These 16 polymorphic EST-SSRs could clearly and effectively distinguish the 28 avocado accessions. In summary, our study is the first presentation of transcriptome data of different avocado ecotypes and comprehensive study on the development and analysis of a set of EST-SSR markers in avocado. The application of next-generation sequencing techniques for SSR development is a potentially powerful tool for genetic studies.
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