Chromosome Doubling of Pepper Haploids Via Chemical or High-Temperature Treatment

In pepper haploid breeding, the low natural doubling rate is a major bottleneck. Artificially inducing haploids chromosome doubling can obtain pepper diploids and improve haploid breeding efficiency. While there is no effective way reported in pepper up to now. This study aimed to investigate the relationship between pepper microsporogenesis and flower development to guide diploid induction and also explore suitable conditions for treatments using chemical reagents and high temperature. The results showed that flower buds developed to stage 2 was most suitable for chemical and high-temperature treatment, when the corolla and anther were green, and the corolla slightly exposed the bracts, and the meiosis were in the zygotene–diplotene phase; the highest induction rate reached 30% when growth points of pepper haploids were treated with 0.006% pendimethalin for 2 days, which is higher than the traditional method of colchicine treatment; the highest induction rate for high-temperature treatment was 14.29%, when the flower buds were subjected to high-temperature treatment at 38 °C for 2 h. The study first report that high-temperature treatment is a feasible method for chromosome doubling of pepper haploids and provide an efficient and practical chemical treatment method for pepper chromosome doubling.