Low acid fruits
Pro Research Analysisby 
Searched over 200M research papers
Understanding Low Acid Fruits: Genetic and Molecular Insights
Introduction to Low Acid Fruits
Low acid fruits are characterized by their reduced acidity, which significantly impacts their taste and consumer preference. The acidity in fruits is primarily determined by the concentration of organic acids such as citric acid and malic acid. This article synthesizes recent research on the genetic and molecular mechanisms underlying low acid traits in various fruits, including apples, peaches, pineapples, melons, cranberries, and litchis.
Genetic Determinants of Fruit Acidity
Apple and Pear Acidity
In apples, fruit acidity is influenced by the malate transporter gene Ma1. A mutation leading to the truncation of this gene results in significantly lower malate transport activity, thereby reducing fruit acidity6. Similarly, in pears, the inheritance of the low-acid trait is linked to specific genetic markers, with the trait being dominant and influenced by both genetic and environmental factors10.
Peach Acidity
In peaches, the D locus plays a crucial role in controlling fruit acidity. Low acidity is determined by a dominant allele at this locus. The D locus is associated with major quantitative trait loci (QTLs) that control fruit pH, titratable acidity, and organic acid concentration2. Additionally, the regulation of malate and citrate accumulation involves several genes, including those in the GABA pathway and malate transporter genes7.
Molecular Mechanisms of Acid Accumulation
Pineapple Acidity
In pineapples, the variation in fruit acidity between high and low acid clones is primarily due to changes in citric acid content. The activity of enzymes such as citrate synthase and aconitase plays a significant role in these changes, particularly in the low acid clone where acidity declines sharply before harvest3.
Melon Acidity
The PH gene in melons is a major determinant of fruit acidity. A specific mutation in this gene, characterized by a four amino-acid duplication, differentiates between acidic and sweet melon varieties. This mutation has been crucial in the evolution of sweet melons, as it reduces fruit acidity4.
Cranberry Acidity
In cranberries, a low citric acid trait has been identified and mapped to a specific locus referred to as CITA. This trait follows a single-gene Mendelian inheritance pattern, with the low acid trait being largely recessive. Marker-assisted selection (MAS) can facilitate the development of reduced acidity cranberry cultivars5.
Integrated Systems Biology Approaches
Sweet Orange Acidity
In sweet oranges, transcriptome analysis has identified several candidate genes involved in citrate accumulation. These genes are part of distinct network modules and are involved in transport, degradation, and transcription processes that regulate fruit acidity8.
Litchi Acidity
In litchis, the variation in fruit acidity is mainly associated with differences in malate and citrate metabolism. Metabolome and transcriptome analyses have identified key pathways and candidate genes responsible for these differences, providing insights into the molecular basis of acidity variation in litchi fruits9.
Conclusion
The genetic and molecular mechanisms underlying low acid traits in fruits are complex and involve multiple genes and pathways. Advances in genetic mapping and molecular biology have provided significant insights into these mechanisms, enabling the development of fruit varieties with desired acidity levels. Understanding these processes is crucial for breeding programs aimed at improving fruit quality and consumer satisfaction.
Sources and full results
Most relevant research papers on this topic
Acidity and sweetness in apple and pear
Apple and pear sweetness and acidity are independently inherited, and their mean acidity and sugar content are significantly determined by their parents, with no clear evidence supporting a single recessive gene.
Phenotypic and fine genetic characterization of the D locus controlling fruit acidity in peach
The D locus in peach has been mapped to a genetic interval of 0.4 cM, providing a first step towards identifying the gene(s) underlying fruit acidity in this fruit.
Pineapple organic acid metabolism and accumulation during fruit development
Pineapple fruit acidity changes during development are mainly due to changes in citric acid content, with the low acid clone showing a sharp decline in acidity just before harvest.
Highly CitedThe PH gene determines fruit acidity and contributes to the evolution of sweet melons
The PH gene determines fruit acidity and contributes to the evolution of sweet melons, with a four amino-acid duplication in CmPH playing a preadaptive role in Central Asia's sweet melon culturing over 1,000 years ago.
Highly Cited