Genetic Analysis and QTL Mapping of Fruit Peduncle Length in Cucumber (Cucumis sativus L.)

Abstract

Mechanized harvesting of cucumbers offers significant advantages compared to manual labor as both shortages and costs of labor increase. However the efficient use of machines depends on breeding plants with longer peduncles, but the genetic and molecular basis of fruit peduncle development in cucumber is not well understood. In this study, F2 populations were developed from a cross between two inbred lines, 1101 with a long peduncle and 1694 with a short peduncle. These were grown at two field sites, Hainan, with a tropical marine climate, in December 2014, and Beijing, with a warm temperate climate, in May 2015. Electron microscope examination of the pith cells in the peduncles of the two parental lines showed that line 1101 had significantly greater numbers of smaller cells compared to line 1694. The inheritance of cucumber fruit peduncle length (FPL) was investigated by the mixed major gene and polygene inheritance model. Genetic analysis indicated that FPL in cucumber is quantitatively inherited and controlled by one additive major gene and additive-dominant polygenes (D-2 model). A total of 1460 pairs of SSR (simple sequence repeat) primers were analyzed to identify quantitative trait loci (QTLs). Two similar genetic maps with 78 SSR markers which covered 720.6 cM in seven linkage groups were constructed based on two F2 populations. QTL analysis from the data collected at the two field sites showed that there are two minor QTLs on chromosome 1, named qfpl1.1 and qfpl1.2, and one major QTL on chromosome 6, named qfpl6.1. The marker UW021226, which was the closest one to qfpl6.1, had an accuracy rate of 79.0% when tested against plants selected from populations of the two parents. The results from this study provide insights into the inheritance and molecular mechanism of the variation of FPL in cucumber, and further research will be carried out to fine map qfpl6.1 to develop more accurate markers for MAS breeding.

Identification of QTL controlling domestication-related traits in cowpea (Vigna unguiculata L. Walp)

“…Some genes involved in plant growth and development were found underlying CPedl5 , including genes belonging to the auxin-responsive GH3 family. In cucumber, two genes belonging to this family ( Csa6G492310 and Csa6G493310 ) were identified as candidates for the main QTL for fruit peduncle length 45 .…”

Quantitative Trait Loci Mapping and Candidate Gene Analysis of Low Temperature Tolerance in Cucumber Seedlings

“…Csa6G445230 encodes EIN2 which is a key regulator in ethylene signaling pathway, and Csa6G445210 encodes ARF which is responsive to auxin. The role of ethylene in abiotic stress resistance including cold responses was established (Yoo et al, 2009;Shi et al, 2012). In Arabidopsis, EIN2 is a positive regulator of the ethylene signaling pathway, indirectly inhibiting the expression of CBFs, which is achieved by the downstream transcription factor EIN3/EILs (Guo and Ecker, 2003;An et al, 2010;Shi et al, 2012;Li et al, 2015).…”

“…The role of ethylene in abiotic stress resistance including cold responses was established (Yoo et al, 2009;Shi et al, 2012). In Arabidopsis, EIN2 is a positive regulator of the ethylene signaling pathway, indirectly inhibiting the expression of CBFs, which is achieved by the downstream transcription factor EIN3/EILs (Guo and Ecker, 2003;An et al, 2010;Shi et al, 2012;Li et al, 2015). CBFs could quickly activate the set of downstream cold-responsive genes COR (i.e., cold regulated genes), to improve plant cold tolerance (Gilmour et al, 1998;Medina et al, 1999;Miura and Furumoto, 2013;Barrero-Gil and Salinas, 2017;Shi et al, 2018).…”

“…However, whether ethylene has a positive or negative effect on cold tolerance might vary among plant species; ethylene may positively regulate a low-temperature response in chilling-sensitive species (Eremina et al, 2016). In A. thaliana, ethylene content decreased when exposed to LT, and the loss-of-function mutant ein2-5 was more resistant to LT stress than the wild-type plants, which indicates that ethylene negatively regulates LT stress response in Arabidopsis (Shi et al, 2012). The same conclusions were drawn in other LT-tolerant plants such as Medicago sativa (Zhao et al, 2014) and Triticum aestivum (Field, 1984).…”

Identification of genetic factors controlling domestication-related traits in cowpea (Vigna unguiculataL. Walp)

“…Some genes involved in plant growth and development were found underlying CPedl5, including genes belonging to the auxin-responsive GH3 family. In cucumber, two genes belonging to this family (Csa6G492310 and Csa6G493310) were identified as candidates for the main QTL for fruit peduncle length (Song et al 2016).…”