Mapping Genes for Sweet Basil's Cold Tolerance and Aroma

Jenn Hoskins
10th April, 2024

Mapping Genes for Sweet Basil's Cold Tolerance and Aroma

Image Source: Natural Science News, 2024

Key Findings

  • Rutgers University identified genes linked to cold tolerance in sweet basil
  • The study found genetic markers for anise-like aroma in basil
  • No genetic markers were found for linalool, a key basil aroma compound, due to low variation
Sweet basil (Ocimum basilicum L.) is a popular herb known for its distinctive aroma and flavor, making it a staple in kitchens and gardens around the world. However, one of the challenges in its cultivation is the plant's sensitivity to cold temperatures, which can lead to chilling injury, manifesting as necrosis or browning of the leaves, and ultimately affecting the herb's marketability and profitability. Rutgers University has been at the forefront of a study[1] aimed at overcoming this issue by identifying genetic markers associated with chilling tolerance and the production of key aroma compounds in sweet basil. The research team from Rutgers University embarked on a quest to identify quantitative trait loci (QTLs), which are segments of DNA that correlate with specific phenotypic traits, such as chilling tolerance and aroma profiles. To accomplish this, they utilized a biparental mapping population derived from a cross between a chilling tolerant line, 'CB15', and a chilling sensitive variety, 'Rutgers Obsession DMR'. The offspring of these two parents, totaling 200 F2 individuals, were assessed for their reaction to cold and their aromatic properties. Chilling tolerance was evaluated by measuring the percentage of leaf necrosis after exposure to low temperatures, using machine learning techniques to enhance accuracy. Aroma profiles were analyzed through gas chromatography-mass spectrometry (GC-MS), a method that can identify and quantify volatile compounds responsible for the herb's scent. To locate the QTLs, the researchers generated single nucleotide polymorphism (SNP) markers from the plant's genomic sequences. These SNPs are variations in a single DNA building block and can serve as genetic signposts. The SNP data were aligned to a reference genome, a valuable resource previously unavailable for basil[2]. This reference genome was crucial in assembling and annotating protein-coding genes, which allowed for a more comprehensive understanding of basil's complex tetraploid genome and its phenylpropanoid pathway, responsible for many of its aromatic properties. The genetic linkage map constructed from the SNP markers led to the discovery of five statistically significant QTLs associated with chilling tolerance, with one, qCH24 on linkage group 24, showing the largest effect across multiple tests. Interestingly, the study did not identify QTLs for linalool, a major aromatic compound in basil, due to insufficient variation in the population for this trait. However, the team did identify two significant QTLs for estragole (methyl chavicol), a compound with an anise-like aroma, which had previously been associated with certain basil varieties[3]. The QTL qEST1 on linkage group 1 was noteworthy in the context of aroma enhancement. Additionally, a significant QTL for eucalyptol (1,8-cineole), another aromatic compound, was identified on linkage group 26, named QEUC26. The findings from this study are significant as they provide a genetic basis for breeding basil varieties with improved chilling tolerance and desired aroma profiles. This could lead to more robust basil plants that can withstand cooler temperatures, extending their growing season and geographic range, and potentially increasing profitability for growers. Moreover, the study's insights into the genetic control of aroma compounds can be leveraged to breed basil varieties that meet consumer preferences for specific flavors. This aligns with previous research that established precise sensory and chemical profiles for basil aroma, linking sensory descriptions with volatile chemistry[3]. Such knowledge is crucial for developing new basil varieties that cater to diverse culinary requirements and consumer tastes. The use of LED lighting in commercial greenhouses has been shown to influence the flavor profiles of basil by affecting the concentrations of flavor volatiles[4]. This technology, when combined with the genetic information provided by Rutgers University's study, could open up new possibilities for manipulating the flavor and hardiness of basil through both environmental control and selective breeding. In conclusion, the study from Rutgers University has made significant strides in understanding the genetic factors that contribute to chilling tolerance and aroma in sweet basil. By utilizing advanced genomic tools and integrating previous research[2][3][4], the team has laid the groundwork for future breeding programs aimed at enhancing the resilience and sensory qualities of this essential culinary herb.

BiotechGeneticsPlant Science

References

Main Study

1) Genetic linkage mapping and quantitative trait locus (QTL) analysis of sweet basil (Ocimum basilicum L.) to identify genomic regions associated with cold tolerance and major volatiles.

Published 9th April, 2024

https://doi.org/10.1371/journal.pone.0299825

Related Studies

2) The genome sequence of tetraploid sweet basil, Ocimum basilicum L., provides tools for advanced genome editing and molecular breeding.

https://doi.org/10.1093/dnares/dsaa027

3) Descriptive aroma profiles of fresh sweet basil cultivars (Ocimum spp.): Relationship to volatile chemical composition.

https://doi.org/10.1111/1750-3841.15797

4) Narrowband Blue and Red LED Supplements Impact Key Flavor Volatiles in Hydroponically Grown Basil Across Growing Seasons.

https://doi.org/10.3389/fpls.2021.623314


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