Ortega Franchesca, Hill Theresa, Van Deynze Allen, Garcia-Llanos Armando, Walker Stephanie
Department of Extension Plant Sciences, New Mexico State University, Las Cruces, NM, United States.
Seed Biotechnology Center, University of California, Davis, Davis, CA, United States.
Front Plant Sci. 2024 Jul 1;15:1357986. doi: 10.3389/fpls.2024.1357986. eCollection 2024.
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.
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.
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.
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.
美国国内辣椒（辣椒属）产量在下降，而国内需求却在增长。劳动力的缺乏和成本问题常常在实际操作和经济层面给国内生产商带来障碍。因此，改用机械采收辣椒被视为帮助国内生产商在国际市场竞争的关键策略。通过育种可以提高机械采收效率。机械采收兼容材料应具备的一个重要特性是易于去梗特性：果梗和花萼与果实的分离力低。
为了检测新墨西哥州豆荚型青椒易于去梗这一新特性的遗传来源，以便未来进行育种工作，我们对三个F2:F3群体进行了数量性状基因座（QTL）分析，这三个群体来自三个新墨西哥州豆荚型品种：“NuMex奥德赛”、“NuMex伊利亚德”和“NuMex乔·E·帕克”，每个品种都与具有易于去梗特性的亲本MUC14杂交。基因分型通过简化基因组测序（GBS）完成，表型分析则针对去梗和果实性状测量进行。通过R包hmisc发现测量值之间的相关性，并通过R/qtl进行QTL分析。
去梗与果实形态特征之间存在密切关系，特别是去梗力与果实宽度（皮尔逊相关系数r = 0.75）。发现了去梗和果实大小的主要QTL。其中，所有群体中最大的去梗力QTL（表型变异解释率（PVE）= 34.5 - 69.9%）位于10号染色体上，在两个群体中，3号染色体上发现了去梗力QTL（PVE = 10.7 - 18.8%）。所有群体中与果实大小相关的QTL都共定位于3号和10号染色体的相同区域。
这表明果实形状可能与去梗存在遗传联系，对选育易于去梗辣椒感兴趣的育种者还必须关注果实大小和形状。
