Determination of heterotic groups for tropical Indica hybrid rice germplasm

Abstract

Two heterotic groups and four heterotic patterns were identified for IRRI hybrid rice germplasm to develop hybrid rice in the tropics based on SSR molecular data and field trials. Information on heterotic groups and patterns is a fundamental prerequisite for hybrid crop breeding; however, no such clear information is available for tropical hybrid rice breeding after more than 30 years of hybrid rice commercialization. Based on a study of genetic diversity using molecular markers, 18 parents representing hybrid rice populations historically developed at the International Rice Research Institute (IRRI) were selected to form diallel crosses of hybrids and were evaluated in tropical environments. Yield, yield heterosis and combining ability were investigated with the main objectives of (1) evaluating the magnitude of yield heterosis among marker-based parental groups, (2) examining the consistency between marker-based group and heterotic performance of hybrids, and (3) identifying foundational hybrid parents in discrete germplasm pools to provide a reference for tropical indica hybrid rice breeding. Significant differences in yield, yield heterosis and combining ability were detected among parents and among hybrids. On average, the hybrids yielded 14.8 % higher than the parents. Results revealed that inter-group hybrids yielded higher, with higher yield heterosis than intra-group hybrids. Four heterotic patterns within two heterotic groups based on current IRRI B- and R-line germplasm were identified. Parents in two marker-based groups were identified with limited breeding value among current IRRI hybrid rice germplasm because of their lowest contribution to heterotic hybrids. Heterotic hybrids are significantly correlated with high-yielding parents. The efficiency of breeding heterotic hybrids could be enhanced using selected parents within identified marker-based heterotic groups. This information is useful for exploiting those widely distributed IRRI hybrid rice parents.

Comparison of three QTL detection models on biochemical, sensory, and yield characters in Coffea canephora

“…Taking this new classification into consideration, breeders will be able to use the genetic diversity available to create mating schemes for determining the heterotic performance of hybrids by assessing marker-based parental groups. This type of experimental design could be of interest for field traits such as yield and disease resistance (Xie et al 2014). However, quality traits could also be managed by this type of study since the biochemical composition throughout the genetic groups is highly variable, especially for caffeine and chlorogenic acids (Ky et al 2001;Campa et al 2004).…”

Genetic differentiation, heterotic performance and grain yield determinate traits of locally adapted sorghum genotypes in contrasting environments in Ethiopia

“…Conventionally, genetic variances of the targeted populations, per se performance and adaptation of the parental lines and the ratio of general combining ability (GCA) to specific combining ability (SCA) have been used to identify heterotic groups (Melchinger, 1999) and the methods have been used in in a number of crops such as triticale and maize (Reif et al, 2005). Molecular markers based genetic distance have also been used to identify heterotic groups in a number of crops including rice (Xie et al, 2014) and triticale . Well established heterotic groups have been developed for maize mainly for the temperate environments (Tracy and Chandler, 2006).…”

“…Both per se performance and combining ability of the inbred parents have been used separately or in combination to predict hybrid performance for different crops including sorghum (Mahama et al, 2014;Kenga et al, 2006); maize (Kebede et al, 2013;Makanda et al, 2010) and rice (Xie et al, 2014). The aforementioned studies have reported positive correlations between inbred per se performance and their hybrid grain yield performance under both drought stress and non-stressed conditions in subtropical and tropical environments.…”

“…Different approaches have been used to identify and develop genetically divergent parental pools that combine consistently to produce high yielding hybrids. Molecular marker-based genetic distance groupings have increasingly been used in a number of crops including rice (Xie et al, 2014), triticale and in maize (Tracy and Chandler, 2006). In sorghum the most widely used grouping of inbred lines for F1 hybrid production is based on fertility restoration and maintainer status of the inbred parents, designated by R and A/B-line groups, respectively (Ahnert et al, 1996;Menz et al, 2004).…”

“…However, these hybrids lack the adaptive traits for the diverse local environment, and additionally had short plant stature and lower grain size and hence do not meet local farmer's needs to be taken up by the Ethiopian farmers. The development of heterotic pools adapted to the local environment is one solution to overcome the challenges of both local adaptation and farmers' end use requirements (Xie et al, 2014;Rattunde et al, 2013). However, in sorghum, such a strategy is complicated by the complex cytoplasmic male sterility system and prevalence of nuclear-encoded restorer genes that imposes on the development of new seed parents (Jordan et al, 2011a).…”