Genetic Control of Reproductive Traits in Tomatoes Under High Temperature

Abstract

Global climate change is increasing the range of temperatures that crop plants must face during their life cycle, giving negative effects to yields. In this changing scenario, understanding the genetic control of plant responses to a range of increasing temperature conditions is a prerequisite to developing cultivars with increased resilience. The current work reports the identification of Quantitative Trait Loci (QTL) involved in reproductive traits affected by temperature, such as the flower number (FLN) and fruit number (FRN) per truss and percentage of fruit set (FRS), stigma exsertion (SE), pollen viability (PV) and the incidence of the physiological disorder tipburn (TB).These traits were investigated in 168 Recombinant Inbred Lines (RIL) and 52 Introgression Lines (IL) derived from the cross between Solanum lycopersicum var. "MoneyMaker" and S. pimpinellifolium accession TO-937. Mapping populations were cultivated under increased temperature regimen conditions: T1 (25 • C day/21 • C night), T2 (30 • C day/25 • C night) and T3 (35 • C day/30 • C night). The increase in temperature drastically affected several reproductive traits, for example, FRS in Moneymaker was reduced between 75 and 87% at T2 and T3 when compared to T1, while several RILs showed a reduction of less than 50%. QTL analysis allowed the identification of genomic regions affecting these traits at different temperatures regimens. A total of 22 QTLs involved in reproductive traits at different temperatures were identified by multi-environmental QTL analysis and eight involved in pollen viability traits. Most QTLs were temperature specific, except QTLs on chromosomes 1, 2, 4, 6, and 12. Moreover, a QTL located in chromosome 7 was identified for low incidence of TP in the RIL population, which was confirmed in ILs with introgressions on chromosome 7. Furthermore, ILs with introgressions in chromosomes 1 and 12 had good FRN and FRS in T3 in replicated trials. These results represent a catalog of QTLs and pre-breeding materials that could be used as the starting point for deciphering the genetic control of the genetic response of reproductive traits at different temperatures and paving the road for developing new cultivars adapted to climate change.

RNA-Seq Highlights Molecular Events Associated With Impaired Pollen-Pistil Interactions Following Short-Term Heat Stress in Brassica napus

“…Recently, the role of plasma membrane-associated ATPases in maintaining plant fertility was reported as these transporters control the ion balance by controlling downstream pH-dependent mechanisms essential for pollen tube growth ( Hoffmann et al, 2020 ). Thus, based on our analysis and previous reports, we suggest that the downregulation of key genes involved in transmembrane transport is one of the key reasons for the loss of pollen function under heat stress conditions ( Frank et al, 2009 ; Giorno et al, 2010 ; Fragkostefanakis et al, 2016 ; Keller et al, 2018 ; Gonzalo et al, 2020 ).…”

“…While high temperature is expected to affect male and female reproductive tissues concurrently, the available data mainly focusses on the effects of heat stress on pollen development and function. Nevertheless, there is a recent focus on the female reproductive organ sensitivity to high temperature in crops like sorghum, rice, maize, wheat, and tomato ( Gonzalo et al, 2020 ; Jagadish, 2020 ; Lohani et al, 2020b ). The outcomes of these studies reveal a considerable variation in heat stress response of pistil (stigma or ovary) across crops.…”

High-Throughput Genotyping of Resilient Tomato Landraces to Detect Candidate Genes Involved in the Response to High Temperatures

“…It has been reported that the wild tomato species usually show high pollen viability and pollen number even under heat stress conditions [ 37 ]. Moreover, it has been demonstrated that some accessions of S. pimpinellifolium exhibit a good level of thermotolerance [ 38 , 39 ].…”

“…It has been reported that two QTLs carrying a S. pimpinellifolium allele and mapping on chromosomes 2 and 4 affect the number of flowers in tomatoes [ 41 ]. Moreover, very recently, a QTL displaying a consistent effect on NFL and TNF was located on the distal region of chromosome 2 in a set of RILs and ILs deriving from a cross between S. lycopersicum and S. pimpinellifolium [ 38 ]. In the present study, we found SNPs and InDels in these same regions, which are currently being investigated.…”

Genetic Analysis of Root-to-Shoot Signaling and Rootstock-Mediated Tolerance to Water Deficit in Tomato

“…The phytaspase 2 coding gene, Solyc04g078740, segregating for an SNP in the RIL population, was found as a candidate gene (and at the QTL peak) for both FlN_C_4 and FlN_WD_4.1 ( Table 2 and Table S5 ). Two QTLs for the number of flowers under high temperatures fln4.1_T2_2E and fln4.1_T3_2E were reported in a similar genetic position using a different RIL population [ 58 ]. Other genes related to the peptide signaling pathway were found within QTL clusters III, VIII, X, and V ( Table 3 and Table S5 ) and cytokinin QTLs ZR_WD_4 (Solyc04g077170), and ZR_WD_10 (Solyc10g011830).…”