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Introduction: Domestic production of pepper (Capsicum spp.) is shrinking while demand within the US is growing. Lack of availability and cost of labor often present an obstacle for domestic producers both practically and economically. As a result, switching to harvesting peppers mechanically is anticipated as a key strategy to help domestic producers compete in the international market. Mechanical harvest efficiency can be improved through breeding. One important trait that mechanical harvest compatible material should have is an easy destemming trait: low force separation of the pedicel and calyx from the fruit. Methods: To detect the genetic sources underlying a novel easy destemming trait for the purpose of future breeding efforts in New Mexico pod-type green chile, we performed QTL analysis on three F2:F3 populations, coming from three New Mexico pod-type varieties: 'NuMex Odyssey,' 'NuMex Iliad,' and 'NuMex Joe E. Parker,' each crossed with a parent with an easy destemming trait: MUC14. Genotyping was done through genotyping by sequencing (GBS) and phenotyping was done for destemming and fruit trait measurements. Correlations between measurements were found through the R package hmisc and QTL analysis was done through R/qtl. Results: A strong relationship was seen between destemming and aspects of fruit morphology, particularly, destemming force and fruit width (Pearson's correlation coefficient r=0.75). Major QTLs for destemming and fruit size were discovered. Of these, the largest destemming force QTLs for all populations (PVE=34.5-69.9%) were on chromosome 10, and in two populations QTLs for destemming force were found on chromosome 3 (Percent Variance Explained (PVE)=10.7-18.8%). Fruit size-related QTLs in all populations colocalized in these same areas on chromosomes 3 and 10. Discussion: This suggests that fruit shape may be genetically linked to destemming, and breeders interested in selecting for easy destemming pepper will also have to pay attention to fruit size and shape.
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Introduction: The majority of peppers in the US for fresh market and processing are handpicked, and harvesting can account for 20-50% of production costs. Innovation in mechanical harvesting would increase availability; lower the costs of local, healthy vegetable products; and perhaps improve food safety and expand markets. Most processed peppers require removal of pedicels (stem and calyx) from the fruit, but lack of an efficient mechanical process for this operation has hindered adoption of mechanical harvest. In this paper, we present characterization and advancements in breeding green chile peppers for mechanical harvesting. Specifically, we describe inheritance and expression of an easy-destemming trait derived from the landrace UCD-14 that facilitates machine harvest of green chiles. Methods: A torque gauge was used for measuring bending forces similar to those of a harvester and applied to two biparental populations segregating for destemming force and rate. Genotyping by sequencing was used to generate genetic maps for quantitative trait locus (QTL) analyses. Results: A major destemming QTL was found on chromosome 10 across populations and environments. Eight additional population and/or environment-specific QTL were also identified. Chromosome 10 QTL markers were used to help introgress the destemming trait into jalapeño-type peppers. Low destemming force lines combined with improvements in transplant production enabled mechanical harvest of destemmed fruit at a rate of 41% versus 2% with a commercial jalapeno hybrid. Staining for the presence of lignin at the pedicel/fruit boundary indicated the presence of an abscission zone and homologs of genes known to affect organ abscission were found under several QTL, suggesting that the easy-destemming trait may be due to the presence and activation of a pedicel/fruit abscission zone. Conclusion: Presented here are tools to measure the easy-destemming trait, its physiological basis, possible molecular pathways, and expression of the trait in various genetic backgrounds. Mechanical harvest of destemmed mature green chile fruits was achieved by combining easy-destemming with transplant management.
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The African Orphan Crops Consortium (AOCC) selected the highly nutritious, fast growing and drought tolerant tree crop moringa (Moringa oleifera Lam.) as one of the first of 101 plant species to have its genome sequenced and a first draft assembly was published in 2019. Given the extensive uses and culture of moringa, often referred to as the multipurpose tree, we generated a significantly improved new version of the genome based on long-read sequencing into 14 pseudochromosomes equivalent to n = 14 haploid chromosomes. We leveraged this nearly complete version of the moringa genome to investigate main drivers of gene family and genome evolution that may be at the origin of relevant biological innovations including agronomical favorable traits. Our results reveal that moringa has not undergone any additional whole-genome duplication (WGD) or polyploidy event beyond the gamma WGD shared by all core eudicots. Moringa duplicates retained following that ancient gamma events are also enriched for functions commonly considered as dosage balance sensitive. Furthermore, tandem duplications seem to have played a prominent role in the evolution of specific secondary metabolism pathways including those involved in the biosynthesis of bioactive glucosinolate, flavonoid, and alkaloid compounds as well as of defense response pathways and might, at least partially, explain the outstanding phenotypic plasticity attributed to this species. This study provides a genetic roadmap to guide future breeding programs in moringa, especially those aimed at improving secondary metabolism related traits.
