Genome wide association analysis of a stemborer egg induced “call-for-help” defence trait in maize

Abstract

Tritrophic interactions allow plants to recruit natural enemies for protection against herbivory. Here we investigated genetic variability in induced responses to stemborer egg-laying in maize Zea mays (L.) (Poaceae). We conducted a genome wide association study (GWAS) of 146 maize genotypes comprising of landraces, inbred lines and commercial hybrids. Plants were phenotyped in bioassays measuring parasitic wasp Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae) attraction to volatiles collected from plants exposed to stemborer Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) eggs. Genotyping-by-sequencing was used to generate maize germplasm SNP data for GWAS. The egg-induced parasitoid attraction trait was more common in landraces than in improved inbred lines and hybrids. GWAS identified 101 marker-trait associations (MTAs), some of which were adjacent to genes involved in the JA-defence pathway (opr7, aos1, 2, 3), terpene biosynthesis (fps3, tps2, 3, 4, 5, 7, 9, 10), benzoxazinone synthesis (bx7, 9) and known resistance genes (e.g. maize insect resistance 1, mir1). Intriguingly, there was also association with a transmembrane protein kinase that may function as a receptor for the egg elicitor and other genes implicated in early plant defence signalling. We report maize genomic regions associated with indirect defence and provide a valuable resource for future studies of tritrophic interactions in maize. The markers identified may facilitate selection of indirect defence by maize breeders.

The role of Desmodium intortum, Brachiaria sp. and Phaseolus vulgaris in the management of fall armyworm Spodoptera frugiperda (J. E. Smith) in maize cropping systems in Africa

“…Studies have also demonstrated that parasitoids could be recruited in anticipation of egg hatching due to the presence of an elicitor, which could be extracted from egg materials associated with attachment to leaves. Genome‐wide association studies (GWAS) on maize cultivars have identified markers associated with plant defence 40 . Such findings suggest selective planting of companion plants to protect maize against FAW.…”

Indigenous African Orphan Legumes: Potential for Food and Nutrition Security in SSA

“…Modern breeding methods including genomics-assisted breeding (GAB) are playing an increasing role in improving the yield and nutrition content in staple crops that cannot be easily and rapidly achieved by conventional breeding (Cerrudo et al, 2018;Mbanjo et al, 2021;Prasanna et al, 2021). Genomic approaches have been utilized in crops for exploring the diversity of collections (Hiremath et al, 2012;Tamiru et al, 2020); precise parental crossing; dense and comprehensive linkage genetic maps (Hiremath et al, 2012;Paliwal et al, 2012;Saxena et al, 2012); quantitative trait loci (QTL) discovery for biotic, abiotic, and nutritional traits (Varshney et al, 2009;Sarvamangala et al, 2011;Paliwal et al, 2012;Jaganathan et al, 2015;Tamiru et al, 2020); and development of improved lines through the introgression of QTL into elite breeding lines (Saghai-Maroof et al, 2008;Varshney et al, 2015). In maize, the genetic gain for heat and drought increased from 4.4 to 19.4% using GAB tools (Cerrudo et al, 2018).…”

Genetic Analysis Reveals Three Novel QTLs Underpinning a Butterfly Egg-Induced Hypersensitive Response-Like Cell Death in Brassica Rapa

“…To date, only a few studies have attempted to map genetic loci associated with insect ovipositioninduced responses [46][47][48][49]. A strong HR-like cell death that eventually leads to egg-killing has been mainly shown for plant species of the tribe Brassiceae (Lineage II), which includes wild species such as Brassica nigra, Sinapis spp., Crambe spp., as well as diverse Brassica crops such as B. napus, B. oleracea and B. rapa but not A. thaliana [11,21,50].…”