In vivo maternal haploid seed production and chromosome doubling with different anti-microtubular agents in maize

Abstract

In maize breeding use of doubled haploids (DH) is very important as these are shortening the time for development of inbred lines. Inbred lines developed through doubled haploid technology are completely homozygous and homogeneous. These inbred lines could be used for heterosis breeding with increased selection efficacy, reduced efforts for line maintenance, reduced length of breeding cycle and convenient applicability of molecular marker assisted breeding. Haploid induction followed by chromosome doubling are practiced for doubled haploid production. Present research emphasized (i) evaluation of four different inducer lines for in-vivo maternal haploid induction and (ii) effectiveness of chromosome doubling with colchicine and pendimethalin herbicide treatments. Haploid induction was done by Stock-6 and three locally produced inducer lines; (I) Stock-6-BC4, (II) Stock-6×CMST×Ig-gene, (III) (Ig-gene×Stock-6×CMST) × (Stock-6-BC4), which were derivatives of Stock6, CMST and Ig-gene. Stock-6, Stock-6-BC4, Stock-6 × (CMST × Ig-gene) and (Ig-gene × Stock-6 × CMST) × (Stock-6-BC4) had 1.01, 2.38, 8.18 and 7.53% average induction rates, respectively. Maternal haploids were identified by using purple color marker gene (R1-nj). Haploids were subjected to colchicine (0.04% colchicine + 0.5% DMSO) and different pendimethalin treatments (0.66, 0.33, 0.165 and 0.0825 ppm) for doubled haploid induction through chromosome doubling. In colchicne treatment, 3.2% plants survived out of which 37.5% reached to maturity and only 50% of these were partially fertile. At 0.66 ppm pendimethalin treatment, 23.3% plants survived out of which 28.57% reached to maturity and only 16.66% plants were partially fertile. Whereas, 0.33, 0.165, 0.0825 ppm treatment showed survival rate of 26.66, 33.33 and 11.11%, respectively but plants showed 100% sterility with sectoral diploidization. Conclusively, local derivative inducer lines viz. Stock-6 × (CMST × Ig-gene) and (Ig-gene × Stock-6 × CMST) × (Stock-6-BC4) showed satisfactorily higher haploid induction rate. These inducer lines are recommended for their further exploitation in haploid induction. For doubled haploid production, 0.66 ppm pendimethalin treatment was more effective in terms of survival, maturity and fertility comparative to all other studied treatments. This indicates that pendimethalin herbicide (0.66 ppm) is an attractive and cost-effective alternative of colchicine.