Evaluation of three sets of advanced backcrosses of eggplant with wild relatives from different gene pools under low N fertilization conditions

Abstract

The development of new cultivars with improved nitrogen use efficiency (NUE) is key for implementing sustainable agriculture practices. Crop wild relatives (CWRs) provide valuable genetic resources for breeding programs aimed at achieving this goal. In this study, three eggplant (Solanum melongena) accessions together with their advanced backcrosses (ABs; BC3 to BC5 generations) were evaluated for 22 morpho-agronomic, physiological, and N use efficiency (NUE) traits under low nitrogen fertilization conditions. The ABs were developed with introgressions from the wild relatives S. insanum, S. dasyphyllum, and S. elaeagnifolium. The AB population comprised a total of 25, 59, and 59 genotypes, respectively, with overall donor wild relative genome coverage percentages of 58.8%, 46.3%, and 99.2%. The three S. melongena recurrent parents were also evaluated under control (normal) N fertilization. Reduction of N fertilization in the parents resulted in decreased chlorophyll content-related traits, aerial biomass, stem diameter and yield, and increased NUE, nitrogen uptake efficiency (NUpE), and nitrogen utilization efficiency (NUtE). However, the decrease in yield was moderate, ranging between 62.6% and 72.6%. A high phenotypic variation was observed within each of the three sets of ABs under low nitrogen conditions, with some individuals displaying improved transgressive characteristics over the recurrent parents. Using the SPET 5k probes platform for high-throughput genotyping, we observed a variable but high degree of recurrent parent genome recovery in the ABs attributable to the lines recombination, allowing the successful identification of 16 QTLs. Different allelic effects were observed for the introgressed QTL alleles. Several candidate genes were identified in the QTL regions associated with plant growth, yield, fruit size, and NUE-related parameters. Our results show that eggplant materials with introgressions from CWRs can result in a dramatic impact in eggplant breeding for a more sustainable agriculture.

Validation and identification of new QTLs for plant and fruit developmental and composition traits in eggplant under low N conditions

“…The incorporation of CWR introgressions into populations with a cultivated background, such as ABs and ILs, enables the development of crop varieties with improved adaptive properties against abiotic stresses related to climate change (Prohens et al, 2017). Previous studies have made efforts to enhance understanding of N use in eggplant, aiming at developing new cultivars with improved N efficiency (Mauceri et al, 2020;Rosa-Martínez et al, 2023;Villanueva et al, 2021Villanueva et al, , 2023a. In this study, introgression lines derived from two eggplant CWRs, S. dasyphyllum and S. insanum, containing genomic regions potentially interesting for adaptation under low N conditions were evaluated together with segregating hybrids derived from them.…”

“…The fertilization solutions were prepared based on the substrate composition and intake water analyses as detailed in Villanueva et al (2023a). The LN fertilization solution was prepared by adding 1.5 mM H 3 PO 4 (Antonio Tarazona SL., Valencia, Spain), 4.85 mM K 2 SO 4 (Antonio Tarazona SL.…”

“…For the study, two accessions of S. melongena (MEL1 and MEL5) were assessed, along with two introgression lines (IL-M1-D2 and IL-M5-I9) derived from MEL1 and MEL5, respectively. The IL-M1-D2 line, derived from S. melongena (MEL1), carries an introgressed fragment on chromosome 2 (6%; 4.9 MB) from the wild relative S. dasyphyllum (accession DAS1) with associated QTLs for chlorophyll content in leaf, aerial plant biomass, and yield (Villanueva et al, 2023a). On the other hand, the IL-M5-I9 was derived from S. melongena (MEL5) with an introgressed fragment on chromosome 9 (60%; 21.5 MB) from the wild relative S. insanum (accession INS1), containing QTLs for flavonol content in leaves, nitrogen balanced index, fruit mean weight, and nitrogen content in leaves and stem.…”

“…This has facilitated the development of interspecific hybrids, advanced backcrosses (ABs), introgression lines (ILs), and MAGIC populations in eggplant breeding (García-Fortea et al, 2019; Gramazio et al, 2017; Kouassi et al, 2016; Mangino et al, 2022; Plazas et al, 2016; Villanueva et al, 2021). In this way, the association of phenotypic and genotypic variation in eggplant has been crucial in identifying quantitative trait loci (QTLs) and candidate genes associated with a broad range of traits (Arrones et al, 2022; Mangino et al, 2021; Portis et al, 2014; Rosa-Martínez et al, 2023; Sulli et al, 2021; Toppino et al, 2020; Villanueva et al, 2023a).…”

“…In a previous study (Villanueva et al, 2023a), QTLs associated with flavonol content in leaves, nitrogen balanced index, fruit mean weight, and nitrogen content in leaves and stem ( fl-9, nb-9, fw-9, nl-9 and ns-9 ) were identified on a genomic region of chromosome 9 (7.4 Mb) in advanced backcrosses (ABs) derived from S. insanum . Additionally, another genomic region was detected on chromosome 2 (4.8 Mb) in ABs of S. dasyphyllum , carrying QTLs for chlorophyll leaf content, aerial plant biomass and yield ( ch-2, bi-2 and yd-2 ).…”