Marker-assisted development and evaluation of near-isogenic lines for scab resistance QTLs of wheat

Abstract

Fusarium head blight or scab resistance in wheat is a complex quantitative trait affected greatly by environments. Therefore, the
quantitative trait loci (QTL) for scab resistance found in mapping projects require validation to be effectively utilized
in breeding programs. In this study, by employing both forward and background selections with the help of molecular markers,
near-isogenic lines (NILs) for scab resistance QTLs Qfh.nau-2B, Qfhs.nau-3B, Qfhi.nau-4B and Qfhi.nau-5A, three of which originating in scab resistance germplasm Wangshuibai, were developed with the elite line Miangyang 99-323
as the recurrent parent. During the process of backcross, selection was based solely on marker genotypes of the target regions,
and on recipient genome recovery rate in BC2F1 and BC3F1. All the identified BC3F1 plants with the target QTL regions have more than 94% recipient genome composition (RGC), and out of four to five of them
a plant with over 97% RGC were obtained in each backcross combination. Compared with Mianyang 99-323, the Qfhs.nau-3B NIL showed much better resistance to disease spread within spikes, the Qfhi.nau-4B and Qfhi.nau-5A NILs showed much better resistance to initial infection, and the Qfh.nau-2B NIL showed improvement in both types of resistance. These results were consistent with findings in the previous QTL mapping
studies. Morphologically and agronomically these NILs were similar to Mianyang 99-323 except that Qfhi.nau-4B NIL was taller and had a longer spike, and Qfhi.nau-5A NIL had narrower leaves. These results demonstrated the feasibility of marker-assisted utilization of scab resistance QTLs.

KeywordsWheat-Scab resistance-QTL-Near-isogenic lines-Marker-assisted selection