title: Pyramids of QTLs enhance host-plant resistance and Bt-mediated resistance to leaf-chewing insects in soybean.
abstract: QTL-M and QTL-E enhance soybean resistance to insects. Pyramiding these QTLs with cry1Ac increases protection against Bt-tolerant pests, presenting an opportunity to effectively deploy Bt with host-plant resistance genes. Plant resistance to leaf-chewing insects minimizes the need for insecticide applications, reducing crop production costs and pesticide concerns. In soybean [Glycine max (L.) Merr.], resistance to a broad range of leaf-chewing insects is found in PI 229358 and PI 227687. PI 229358's resistance is conferred by three quantitative trait loci (QTLs): M, G, and H. PI 227687's resistance is conferred by QTL-E. The letters indicate the soybean Linkage groups (LGs) on which the QTLs are located. This study aimed to determine if pyramiding PI 229358 and PI 227687 QTLs would enhance soybean resistance to leaf-chewing insects, and if pyramiding these QTLs with Bt (cry1Ac) enhances resistance against Bt-tolerant pests. The near-isogenic lines (NILs): Benning(ME), Benning(MGHE), and Benning(ME+cry1Ac) were developed. Benning(ME) and Benning(MGHE) were evaluated in detached-leaf and greenhouse assays with soybean looper [SBL, Chrysodeixis includens (Walker)], corn earworm [CEW, Helicoverpa zea (Boddie)], fall armyworm [FAW, Spodoptera frugiperda (J.E. Smith)], and velvetbean caterpillar [VBC, Anticarsia gemmatalis (Hübner)]; and in field-cage assays with SBL. Benning(ME+cry1Ac) was tested in detached-leaf assays against SBL, VBC, and Southern armyworm [SAW, Spodoptera eridania (Cramer)]. In the detached-leaf assay, Benning(ME) showed the strongest antibiosis against CEW, FAW, and VBC. In field-cage conditions, Benning(ME) and Benning(MGHE) suffered 61 % less defoliation than Benning. Benning(ME+cry1Ac) was more resistant than Benning(ME) and Benning (cry1Ac) against SBL and SAW. Agriculturally relevant levels of resistance in soybean can be achieved with just two loci, QTL-M and QTL-E. ME+cry1Ac could present an opportunity to protect the durability of Bt genes in elite soybean cultivars. These results should assist the development of effective pest management strategies, and sustainable deployment of Bt genes in soybean.
authors.affiliation: Institute of Plant Breeding, Genetics and Genomics, University of Georgia, 111 Riverbend Rd., Athens, GA, 30602, USA.
authors.forename: María A
authors.initials: MA
authors.lastname: Ortega
authors.affiliation: Department of Entomology, University of Georgia, 413 Biological Sciences Building, Athens, GA, 30602, USA.
authors.forename: John N
authors.initials: JN
authors.lastname: All
authors.affiliation: Institute of Plant Breeding, Genetics and Genomics, University of Georgia, 111 Riverbend Rd., Athens, GA, 30602, USA.
authors.forename: H Roger
authors.initials: HR
authors.lastname: Boerma
authors.affiliation: Institute of Plant Breeding, Genetics and Genomics, University of Georgia, 111 Riverbend Rd., Athens, GA, 30602, USA. wparrott@uga.edu.
authors.forename: Wayne A
authors.initials: WA
authors.lastname: Parrott
mesh_terms: D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics*; D004731:Endotoxins / Q000235:genetics*; D008040:Genetic Linkage; D006460:Hemolysin Proteins / Q000235:genetics*; D009036:Moths; D010572:Pest Control, Biological; D030821:Plants, Genetically Modified / Q000235:genetics; D040641:Quantitative Trait Loci; D013025:Glycine max / Q000235:genetics*
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis