Low temperature increases the frequency of 2n female gametes in the diploid rubber tree (Hevea brasiliensis (Willd. ex A.Juss.) Müll. Arg.)

Abstract

Triploid breeding via the fusion of 2n gametes and n gametes is an efficient method for breeding new varieties in woody plants. Triploid plants are frequently observed in the seedlings of the diploid rubber clone GT1. However, the factors affecting the occurrence and source of triploid progeny in GT1 are still unknown. In this study, the correlation between temperature and triploid progeny frequency in GT1 in different environments over 6 years was analyzed to evaluate the influence of temperature on the frequency of 2n female gametes. A total of 76 triploid progenies were analyzed using 19 simple sequence repeat markers, with the aim of revealing their genetic origin and the mechanism underlying 2n megagametophyte formation. The results showed that low temperature increased the frequency of triploid progeny in GT1, and the determination of allelic status revealed that all triploids were derived from the 2n female gametes, thereby confirming that low temperature increased the frequency of 2n female gametes. The rate of maternal heterozygosity restitution (HR) of seven loci varied from 2.70 to 67.65% with a mean value of 40.56%, and the rate of maternal HR of 37 triploids varied from 14.29 to 66.67% with a mean value of 41.38%, indicating that the production of 2n eggs in the triploid seedlings of GT1 was by second division restitution. The results of this study are valuable for the polyploid breeding of rubber trees.