Location: Corn Host Plant Resistance Research
Project Number: 6064-21000-018-005-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 20, 2025
End Date: Sep 19, 2027
Objective:
(I) Incorporate resistance to both corn stunt pathogen S. kunkelli and A. flavus into adapted commercial inbred lines with expired Plant Variety Protection (ex-PVP); (II) utilize doubled haploid (DH) technology to expedite development of inbreds from F1 populations derive from crosses between F1 plants with resistance to S. kunkelli and F1 plants with resistance to A. flavus infection and aflatoxin accumulation; and (III) screen and select within segregating populations for DH lines that combine resistance to both S. kunkelli and A. flavus infection with earlier flowering, and improved agronomic qualities.
Approach:
Combining resistance to S. kunkelli with A. flavus, and drought and heat tolerance would be the ideal management strategy. Despite the invaluable alleles for resistance to S. kunkelli and A. flavus in CIMMYT germplasm, they often possess undesirable agronomic traits such as late flowering, tall plants with increased lodging, and decreased yield potential. It is, therefore, necessary to breed second cycle lines using CIMMYT resistant lines as donors and adapted commercial inbred lines with expired Plant Variety Protection (ex-PVP) as recurrent parents. During the last two years, our unit has evaluated 90 ex-PVP lines for adaptation, and agronomic potential at Mississippi and Georgia and four lines, PHMK0, PHKV1, PHN82, and PHGV6, with significant positive general combing ability (GCA) effect on grain yield were identified. In this project we will utilize double haploid technology to expedite development of inbreds from F1 populations developed from crosses between CIMMYT inbred line CML 247 with resistance to both corn stunt and A. flavus kernel infection and four ex-PVP lines.
With classical breeding, obtaining a genetically homozygous maize line requires eight generations of inbreeding. However, doubled haploid (DH) enables derivation of genetically homozygous lines in just two generations. Producing homozygous inbred lines derived from crosses in a short time will shorten the breeding cycle and accelerate genetic improvement. The F1 population derived from crosses will be sent to the collaborator at the DH facility at Iowa State University. The University developed an inducer line that allows the induction and selection of haploid kernels in colored inducer backgrounds based on the C1-I allele. Doubled haploid seeds will be sent back to ARS PI for field screening at Mississippi State, MS, USA. Resistant germplasm identified will be used in future breeding activities to conduct test cross trials to select lines with improved GCA for yield, and alignment with industry heterotic patterns. By leveraging these populations, we are hoping to identify germplasm with resistance coupled with drought and heat tolerance. Further, the resulting doubled haploid lines will be used for genetic analysis to identify and deploy genes and QTLs associated with resistance.