Improved drought stress tolerance of white clover through hybridisation with Trifolium uniflorum L.

Abstract

The objective of this study was to determine the effect of hybridisation with Trifolium uniflorumL. on drought resistance of Trifolium repens L. (white clover). Shoot dry weight of backcross 1 (BC1) hybrids was reduced less by water stress than for backcross 2 (BC2) hybrids and white clover, as were key morphological traits such as leaf area. Under water stress, important differences for the BC1 generation compared to white clover also included lower senescence, higher stolon density, increased root dry weight, and a higher maximum nodal root diameter. Drought decreased the net photosynthetic rate by up to 48% in BC2 and white clover, but there was no significant effect on the BC1 generation. BC1 hybrids were therefore more resistant to water stress than white clover. Smaller effects on stolon morphology suggest BC1 hybrids were better able to maintain cell turgor and growth, and maintenance of photosynthesis under drought may have contributed to smaller reductions in productivity. The findings suggest that BC1 hybrids may be able to maintain higher water uptake during drought than white clover by increased allocation to root biomass.