Induction of 2n female gametes in rubber (Hevea brasiliensis) by high-temperature exposure during megasporogenesis as a basis for triploid breeding

Abstract

In this study, 2n gametes were induced in the rubber tree RRIM 600 by high-temperature exposure and used for the production of triploid offspring. A relationship between megasporogenesis and the external morphology of male and female flower buds was established to guide the treatments. The relationship between megasporogenesis and microsporogenesis of adjacent male flower buds was also estimated. The developmental stage of megasporogenesis was estimated indirectly based on these relationships. Finally, 5 open-pollinated triploid offspring were obtained; the mean efficiency of triploid production was approximately 1.2%. The induction efficiency was approximately 9.1% when meiotic stages of megasporogenesis from the diplotene stage to the diakinesis stage were exposed to a high temperature of 44 °C for 4 h. Simple sequence repeat (SSR) markers revealed that the 2n gametes were derived from the RRIM 600 female parent. This study was the first to induce 2n female gametes in rubber trees and will serve as the basis for the germplasm creation of triploids and breeding of new varieties of rubber trees.