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Article|07 Mar 2022|OPEN
QTL mapping and genomic analyses of earliness and fruit ripening traits in a melon recombinant inbred lines population supported by de novo assembly of their parental genomes
Elad Oren1,2 , Galil Tzuri1 , Asaf Dafna1 , Evan R. Rees3 , Baoxing Song3 , Shiri Freilich1 , Yonatan Elkind2 , Tal Isaacson1 , Arthur A. Schaffer4 , Yaakov Tadmor1 , Joseph Burger1 and Edward S. Buckler3,5 , Amit Gur,1 ,
1Plant Science Institute, Agricultural Research Organization, Newe Ya’ar Research Center, P.O. Box 1021, Ramat Yishay 3009500, Israel
2The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot, Israel
3Plant Breeding and Genetics Section, Cornell University, Ithaca, NY 14853, USA
4Plant Science Institute, Agricultural Research Organization, The Volcani Center, P.O. Box 15159, Rishon LeZiyyon 7507101, Israel
5United States Department of Agriculture-Agricultural Research Service, Robert W. Holley Center for Agriculture and Health, Ithaca, NY 14853, USA
*Corresponding author. E-mail: amitgur@volcani. agri.gov.il

Horticulture Research 9,
Article number: uhab081 (2022)
doi: https://doi.org/10.1093/hr/uhab081
Views: 237

Received: 14 Sep 2021
Accepted: 04 Nov 2021
Published online: 07 Mar 2022

Abstract

Earliness and ripening behavior are important attributes of fruits on and off the vine, and affect quality and preference of both growers and consumers. Fruit ripening is a complex physiological process that involves metabolic shifts affecting fruit color, firmness, and aroma production. Melon is a promising model crop for the study of fruit ripening, as the full spectrum of climacteric behavior is represented across the natural variation. Using Recombinant Inbred Lines (RILs) population derived from the parental lines “Dulce” (reticulatus, climacteric) and “Tam Dew” (inodorus, non-climacteric) that vary in earliness and ripening traits, we mapped QTLs for ethylene emission, fruit firmness and days to flowering and maturity. To further annotate the main QTL intervals and identify candidate genes, we used Oxford Nanopore long-read sequencing in combination with Illumina short-read resequencing, to assemble the parental genomes de-novo. In addition to 2.5 million genome-wide SNPs and short InDels detected between the parents, we also highlight here the structural variation between these lines and the reference melon genome. Through systematic multi-layered prioritization process, we identified 18 potential polymorphisms in candidate genes within multi-trait QTLs. The associations of selected SNPs with earliness and ripening traits were further validated across a panel of 177 diverse melon accessions and across a diallel population of 190 F1 hybrids derived from a core subset of 20 diverse parents. The combination of advanced genomic tools with diverse germplasm and targeted mapping populations is demonstrated as a way to leverage forward genetics strategies to dissect complex horticulturally important traits.