Indian J. Genet., 79(4) 678-684 (2019) DOI: 10.31742/IJGPB.79.4.5 *Corresponding author’s e-mail: rajesh.khulbe@icar.gov.in Published by the Indian Society of Genetics & Plant Breeding, A-Block, F2, First Floor, NASC Complex, IARI P.O., Pusa Campus, New Delhi 110 012; Online management by www.isgpb.org; indianjournals.com R1-nj expression in parental inbreds as a predictor of amenability of maize hybrids to R1-nj-based doubled haploid development R. K. Khulbe*, A. Pattanayak and Vivek Panday ICAR-Vivekananda Parvatiya Krishi Anusandhan Sansthan, Almora 263 145, Uttarakhand (Received: May 2019; Revised: July 2019; Accepted: September 2019) Introduction Doubled haploid (DH) development has emerged as a promising method for rapid generation of completely homozygous lines for accelerating hybrid development process in maize. The current method of DH development in maize involves in vivo production of haploids using R1-nj based haploid inducer lines that upon use as male render a small fraction of seed in the female ears haploid (Prasanna et al. 2012). The haploid seeds are subsequently diploidized to obtain completely homozygous lines. Identification of haploids at seed stage is based on phenotypic expression of R1-nj (Navajo phenotype), which is characterized by purple colouration in the aleurone layer on the crown region of the endosperm and the scutellum of the embryo (Nanda and Chase 1966; Greenblatt and Bock 1967). R1-nj is an allele of R1 regulatory gene which regulates kernel anthocyanin biosynthesis and its expression requires other structural genes involved in anthocyanin biosynthesis pathway (Chase 1969; Geiger 2009). The use of this method, however, is limited by the presence of dominant anthocyanin inhibitor genes (C1-I, C2-Idf and in-1D) that inhibit anthocyanin biosynthesis in maize endosperm and embryo (Coe et al. 1988; Stinard and Sachs 2002). Depending on the homozygosity or heterozygosity of the inhibitor alleles in the source population, R1-nj expression may be completely inhibited in all kernels or may segregate for color expression among the kernels in an induction cross. This reduces the efficiency of haploid identification based on crosses of source germplasm with the R1-nj-based haploid inducers (Chaikam et al. 2015) and may altogether render potential source germplasm unsuitable for DH Abstract The current method of doubled haploid (DH) development in maize involves in vivo production of haploids using R1- nj-based haploid inducer lines that upon use as male render a small fraction of seed in the pollinated female ears haploid. Identification of haploid seed relies on R1-nj marker expression in the endosperm and embryo, and the degree of its expression determines efficiency of DH development process. In the present study, R1-nj expression in the endosperm was characterized in crosses of CIMMYT’s R1- nj-based haploid inducer TAILP1 with a set comprising 18 early maturity hybrids and their 23 parental inbreds. Kernel colour inhibition was observed only in a small proportion of the hybrids and inbreds. Comparison of R1-nj expression in the hybrids and their parental inbreds revealed a distinct pattern, which may be useful in identifying source populations and/or determining parental constituents for synthesizing source populations with predicted amenability to doubled haploid development using R1-nj-based haploid inducers. However, deviation from the pattern was noted in hybrids involving inbreds with higher degree of colour inhibition, which suggests complex nature of R1-nj phenotype expression and necessitates further investigation involving larger sets of germplasm for dissecting the role of maternal and paternal genetic factors in determining R1-nj phenotype expression. The hybrids found exhibiting complete kernel anthocyanin expression in present study can be used directly as source populations for DH development using R1-nj based haploid inducers. Besides, since the inbreds used in the study have originated from and/or are accessible to CGIAR/NARS maize breeding programmes, the information on their kernel anthocyanin expression can be helpful in selection of source populations or generating new source populations amenable for DH development using R1-nj based haploid inducers. Key words : Maize, haploid inducer, R1-nj expression, doubled haploid, amenability