Kai Wang, Fulin Qiu, Wenceslao Larazo, Madonna Angelita dela Paz, Fangming Xie

Theoretical and Applied Genetics; March 2015, Volume 128, Issue 3, pp 421-430

http://link.springer.com/article/10.1007/s00122-014-2441-5

Abstract

Key message

Four heterotic groups were identified for tropical indica rice germplasm to develop hybrid rice in the tropics based on two studies.

Abstract

Heterotic groups are of fundamental importance in hybrid crop breeding. This study investigated hybrid yield, yield heterosis and combining ability within and among groups based on genetic distance derived from single-nucleotide polymorphism markers. The main objectives of the study were to (1) evaluate the magnitude of yield heterosis among marker-based groups, (2) identify possible heterotic groups for tropical indica hybrid rice, and (3) validate heterotic patterns concluded from a previous study. Seventeen rice parents selected from improved indica germplasm from the tropics with high genetic divergence and 136 derived hybrids were evaluated in five environments. The hybrids had more yield than their parents with an average of 24.1 % mid-parent heterosis. Genotype × environment interaction was the major factor affecting variations in yield and yield heterosis, which raised a necessity and a challenge to develop heterotic rice hybrid adapted to different regions and seasons in the tropics. Yield, yield heterosis and combining ability were significantly increased in inter-group than in intra-group hybrids. Four heterotic groups and three promising hybridization patterns, which could be used in tropical hybrid rice breeding, were identified based on marker-based grouping, yield and yield heterosis analyses in the two studies. The study reveals that molecular markers analysis can serve as a basis for assigning germplasm into heterotic groups and to provide guidelines for parental selection in hybrid rice breeding.

Fig. 4  Cluster of the 35 tropical indica parents from two heterotic studies based on genetic distance calculated from 384 SNP markers. Letters G and B indicate groups from the previous (Xie et al. 2014) and present studies, respectively, and numbers refer to the marker-based groups in the two studies