In Vivo Haploid Induction in Maize: Identification of Haploid Seeds by Their Oil Content

ABSTRACT In vivo haploid induction has become a routine tool for rapid line development in maize (Zea mays L.). However, distinguishing haploid (H) from diploid crossing (C) seeds is problematic for many germplasms due to poor expression or suppression of the currently‐used R1‐nj embryo marker. We examined a new approach for sorting H and C seeds on the basis of their oil content (OC). Ten source germplasms, including single crosses, synthetics, and landraces, were pollinated by high‐oil (HO) inducer UH600 with OC = 10.8%. Identification of embryoless seeds based on seed OC < 2.1% was very reliable. The average difference (1.79%) between the mean OC of C and H seeds was more than twice the standard deviation (SD) within each fraction. Thus, sorting H and C seeds based on OC smaller or greater than an a priori chosen threshold t was generally more reliable than based on the R1‐nj embryo marker. Another ten source germplasms were pollinated with normal‐oil inducer UH400 with OC = 3.0%. Since the difference (0.65%) between OC of C and H seeds was approximately of the same magnitude as the SD, both fractions overlapped too much for reliable sorting. The discrimination of H and C seeds based on their OC looks very promising, even for heterogeneous source materials such as landraces, provided an HO inducer and a stringent threshold t are used. In combination with high‐throughput platforms for automated sorting of single seeds for OC, this opens new avenues for extending the application and increasing the efficiency of the double haploid technology in maize.