QTL mapping of parthenocarpic fruit set in North American processing cucumber

Authors: LIETZOW, CALVIN - University Of Wisconsin; ZHU, HUAYU - University Of Wisconsin; PANDEY, SUDHAKAR - Indian Institute Of Horticultural Research; Havey, Michael; Weng, Yiqun

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2016
Publication Date: 8/31/2016
Publication URL: http://handle.nal.usda.gov/10113/5642513
Citation: Lietzow, C.D., Zhu, H., Pandey, S., Havey, M.J., Weng, Y. 2016. QTL mapping of parthenocarpic fruit set in North American processing cucumber. Theoretical and Applied Genetics. 129(12):2387-2401. doi: 10.1007/s00122-016-2778-z.

Interpretive Summary: Parthenocarpy is a desirable trait with potential for increasing yield and quality in processing cucumber production. Although many successful parthenocarpic fresh market cucumber varieties have been developed, the genetic and molecular mechanisms behind parthenocarpic expression in cucumber remain largely unknown. Since parthenocarpy is an important yield component, it is difficult to separate the true parthenocarpic character from other yield related traits. In the present study, we developed a novel phenotypic approach for parthenocarpic fruit set focusing on early fruit development. Two hundred and five F3 families derived from a cross between the highly parthenocarpic line 2A and low parthenocarpic line Gy8 were phenotypically evaluated in three greenhouse experiments. Seven QTLs associated with parthenocarpic fruit set were detected. Among them, one each on chromosomes 5 and 7 (parth5.1 and parth7.1) and two on chromosome 6 (parth6.1 and parth6.2) were consistently identified in all experiments, but their relative contribution to the total phenotypic variation was dependent on plant growth stages. While each of the four QTL had almost equal contribution to the expression of the trait at commercial harvest stage, parth7.1 played a more important role in early parthenocarpic fruit set. The results suggested that parthenocarpic fruit set can be accurately evaluated with as few as 20 nodes of growth. The QTLs identified in this study for parthenocarpic fruit set are a valuable resource for cucumber breeders interested in developing parthenocarpic cultivars and to researchers interested in the genetic and molecular mechanisms of parthenocarpic fruit set.

Technical Abstract: Parthenocarpy is a desirable trait with potential for increasing yield and quality in US processing cucumber production. Many successful parthenocarpic fresh market cucumber varieties have been developed, but the genetic and molecular mechanisms for parthenocarpic expression in cucumber is largely unknown. Since parthenocarpy is an important yield component, it is difficult to separate the true parthenocarpic character from other yield related traits. In the present study, we developed a novel phenotypic approach for parthenocarpic fruit set focusing on early fruit development. We developed 205 F3 families by crossing the highly parthenocarpic line 2A with low parthenocarpic line Gy8. Phenotypic data were collected in three greenhouse experiments. Seven QTLs associated with parthenocarpic fruit set were detected. Among them, one each on chromosomes 5 and 7 and two on chromosome 6 were consistently identified in all experiments, but their relative contribution to the total phenotypic variation was dependent on plant growth stages. While each of the four QTL had almost equal contribution to the expression of the trait at commercial harvest stage, the chromosome 7 QTL played a more important role in early parthenocarpic fruit set. The results suggested that parthenocarpic fruit set can be accurately evaluated with as few as 20 nodes of growth. The QTLs identified in this study for parthenocarpic fruit set are a valuable resource for cucumber breeders interested in developing parthenocarpic cultivars and to researchers interested in the genetic and molecular mechanisms of parthenocarpic fruit set.