Male Parent Identification of Triploid Rubber Trees (Hevea brasiliensis) and the Mechanism of 2n Gametes Formation

Abstract

Eight triploids were screened among offspring of the rubber tree clone GT1 × different clones by flow cytometry and chromosome counting. Twenty-five simple sequence repeat (SSR) markers were screened to identify the origin of 2n gametes, to determine the male parents of these triploids, and to evaluate the mechanism of 2n gamete formation using band configurations and microsatellite DNA allele counting peak ratios (MAC-PR). The results showed that 2n gametes originated from the maternal rubber tree clone GT1, contributing the extra genome copy present in the triploids. It was confirmed that GT1 is able to produce a 2n megagametophyte spontaneously. Many male parents were shown to provide pollen for formation of triploid rubber trees, including clones RRIC 103, Yunyan 277-5, and three other clones. The second division restitution (SDR) was likely the main mechanism involved in formation of megagametophytes in GT1, as the rate of maternal heterozygosity restitution (HR) of all eight triploids varied from 27.78% to 75.00%, with a mean of 51.46%, and all 25 markers varied from 0% to 100%, with a mean of 51.69%. Elucidation of the origin and formation of 2n gametes will help optimize further sexual hybridization of polyploid rubber trees.

Microsporogenesis and Induction of Unreduced Pollen with High Temperatures in Rubber Tree Clone RRIM 600

“…Further application of these polyploid was not reported. Although triploid clones Yunyan 77-2 and Yunyan 77-4 have been selected from the natural rubber trees population and were reported in 2009 by Li et al [4], no efforts had been made to understand the mechanism of triploid until Yao et al [11] reported that rubber tree clone GT 1 can produce 2n megagametophyte spontaneously, which will provide reasonable guidance for polyploid induction using 2n gametes.…”

“…Yunyan 77-2 and Yunyan 77-4 both were selected from GT 1 (Gondang Tapen, Indonesia) × PR 107 (Profestation voor Rubber, Indonesia) [9,10]. Yao et al [11] has proved that rubber tree clone GT 1 is able to produce 2n megagametophyte spontaneously. At present, no unreduced pollen has been reported in rubber trees.…”

Research progress and prospect of triploid breeding of forest trees

“…美洲黑杨、欧洲山杨也存在可自然产生 2n配子的雌株 [31,32] . 这种由天然2n配子生产的三倍体 品种实际已经在生产中得到应用, 如我国云南广泛栽 培的"云研77-2"、"云研77-4"橡胶树三倍体品种起源 于母本"GT1"自然发生的2n雌配子 [33] . 而三倍体毛白 杨系列品种则来源于天然2n花粉授粉杂交 [8] .…”

The DcPS1 cooperates with OSDLa during pollen development and 2n gamete production in carnation meiosis

“…The use of unreduced gametes in plant breeding has led to the establishment of sexual polyploids and has played an important role in the improvement of crops such as carnation [ 8 ], Japanese persimmon [ 9 ], lemon [ 10 ], lily [ 11 , 12 ], poplar [ 13 ], potato [ 14 ], rose [ 15 , 16 ] and rubber trees [ 17 ]. Triploids with important horticultural traits, such as vigorous growth and large flowers, were identified in tulip 2x × 2x hybrid progenies [ 18 ].…”