Inheritance of cell size in wheat (Triticum aestivum L.) and its relationship to the vernalization loci

Reduced cell size is an important adaptive feature in plant response to environmental stresses. The objectives of the present study were to determine the inheritance and location of genes controlling cell size and to establish the relationship between cell size, low-temperature (LT) tolerance, and growth habit as determined by the Vrn loci in wheat. Guard cell length was measured in F-1, F-2, and F-2-derived F-3 populations from parents ranging widely in cell size and in the Chinese Spring/Cheyenne (CS/CNN) chromosome substitution series. The cell size of F-1 hybrids was similar to the parental midpoint and the F-2 frequency distribution was symmetrical about the mean indicating that cell size was determined by additive gene action with little or no dominance. It appears that there are several genes involved since none of the F-2 progeny had a cell size as large or as small as the parental mean range. The cell size of the homozygous spring and winter lines from F-2-derived F-3 populations fell into two distinct groups that were related to plant growth habit. Large cell size was associated with the spring-habit alleles (Vrn-A1) and small cell size was associated with the winter-habit alleles (vrn-A1) on chromosome 5A. Analyses of the CS/CNN chromosome substitution series showed that CNN chromosomes 5A and 5B both reduced cell size without changing the growth habit, indicating that growth habit per se does not determine cell size. The group-5 chromosomes therefore appear to carry homoeologous alleles with major effects on cell size in wheat. This places cell-size control and many other low-temperature (LT) tolerance associated characters in close proximity to the vrn region of the group-5 chromosomes.