Genetic and Cytological Analysis of a Novel Type of Low Temperature-Dependent Intrasubspecific Hybrid Weakness in Rice

Abstract

Hybrid weakness (HW) is an important postzygotic isolation which occurs in both intra- and inter-specific crosses. In this study, we described a novel low temperature-dependent intrasubspecific hybrid weakness in the F1 plants derived from the cross between two indica rice varieties Taifeng A and V1134. HW plants showed growth retardation, reduced panicle number and pale green leaves with chlorotic spots. Cytological assay showed that there were reduced cell numbers, larger intercellular spaces, thicker cell walls, and abnormal development of chloroplast and mitochondria in the mature leaves from HW F1 plants in comparison with that from both of the parental lines. Genetic analysis revealed that HW was controlled by two complementary dominant genes Hw3 from V1134 and Hw4 from Taifeng A. Hw3 was mapped in a 136 kb interval between the markers Indel1118 and Indel1117 on chromosome 11, and Hw4 was mapped in the region of about 15 cM between RM182 and RM505 on chromosome 7, respectively. RT-PCR analysis revealed that only LOC_Os11g44310, encoding a putative calmodulin-binding protein (OsCaMBP), differentially expressed among Taifeng A, V1134 and their HW F1. No recombinant was detected using the markers designed based on the sequence of LOC_Os11g44310 in the BC1F2 (Taifeng A//Taifeng A/V1134) population. Hence, LOC_Os11g44310 was probably the candidate gene of Hw3. Gene amplification suggested that LOC_Os11g44310 was present in V1134 and absent in Taifeng A. BLAST search revealed that LOC_Os11g44310 had one copy in the japonica genomic sequence of Nipponbare, and no homologous sequence in the indica reference sequence of 9311. Our results indicate that Hw3 is a novel gene for inducing hybrid weakness in rice.

The importance of reproductive barriers and the effect of allopolyploidization on crop breeding

“…Segregation tests revealed that type II and type III necrosis are associated with a single genetic locus on the short arm of the D genome, chromosome 7D and 2D, respectively ( Mizuno et al 2010 , 2011 ). Temperature-dependent hybrid weakness is also observed in inter-specific hybrids in rice ( Chen et al 2014 , Fu et al 2013 ). One high-temperature dependent hybrid weakness is caused by the interaction between Hwi1 in wild rice, Oryza furipogon , and Hwi2 in indica rice, Oryza sativa ( Chen et al 2014 ).…”

An overview on reproductive isolation inOryza sativacomplex

“…3. In addition to the crop-wild (interspecific) and indica – japonica (inter-subspecific) reproductive barriers, some barriers also exist between intra-subspecific hybridizations ( indica – indica and japonica – japonica ) ( Zhang 2012 ; Fu et al 2013 ). The hybrid weakness observed in the intra-subspecific hybridization ( indica – indica and japonica – japonica ) needs evolutionary as well as molecular analysis.…”

Evolution and Molecular Control of Hybrid Incompatibility in Plants

“…This conditionally expressed RI is also observed in plants. Most of the hybrid necrosis or weakness cases that have been studied so far are temperature sensitive ( Bomblies et al, 2007 ; Saito et al, 2007 ; Alcázar et al, 2009 ; Fu et al, 2013 ; Chen et al, 2014 ). Usually, low temperature promotes the expression of inferior symptoms.…”