Alternatives to colchicine for obtaining doubled haploids in tropical white corn

Colchicine is a widely used and effective agent for producing doubled haploid inbred lines in maize. However, its high toxicity and cost have prompted the search for safer and more economical alternatives for chromosome doubling. This study aimed to evaluate the effectiveness of pronamide and amiprophos-methyl solutions as alternatives to colchicine for chromosome doubling in tropical white corn (Zea mays L.), to identify the potential for spontaneous chromosomal doubling in tropical white maize populations, and to compare the haploid induction rates of three tropicalized inducer lines (CIM2GTAIL-P1, CIM2GTAIL-P2, and CIM2GTAIL-P3) along with their three hybrid combinations in crosses with tropical white corn. Eight populations of white corn were pollinated by six inducer genotypes, and the haploid induction rates were estimated. At the V2 stage, the roots of the haploid seedlings were washed and immersed in four treatments for chromosome doubling: a negative control with water, an amiprofos-methyl and pronamide solution, a colchicine solution, and a pronamide solution. Parameters such as self-pollination rate, self-pollination efficiency, survival, reproduction, and overall success were estimated. The amiprofos-methyl and pronamide treatment proved to be an effective alternative for the production of doubled haploid lines in tropical white corn, successfully replacing the use of colchicine. The tropical white corn populations presented spontaneous chromosome doubling rates ranging from 7.9% to 38.3%. The CIM2GTAIL-P1 × CIM2GTAIL-P2 hybrid demonstrated the highest haploid induction rate, with an average of 12.9%.