Drought resistance of C₄ grasses under field conditions: genetic variation among a large number of bermudagrass ( Cynodon spp.) ecotypes collected from different climatic zones

Abstract

Predictions of extreme weather resulting from climate change will present huge challenges for scientists trying to maintain and increase agricultural production. A greater frequency of dry periods is predicted placing emphasis on the development of plant varieties that are able to maintain performance in dry conditions. The aim of this research was to determine the genetic variation for drought resistance among a large range of potential pasture or turf bermudagrasses (Cynodon spp.). Four hundred and sixty genotypes including ecotypes collected from different climatic zones of Australia, and commercial cultivars were established in the field and assessed during natural and imposed drought periods. Using descriptors of drought resistance such as turf quality and green cover, genotypes were classified into different groups; 436 genotypes were clustered into ten groups in one experiment, and 72 genotypes were clustered into three groups in a second. There was a high correlation of response (r = 0.78) for 47 genotypes common to both experiments suggesting that the drought resistance techniques used to group genotypes were robust. Physiological analyses of the genotypes within the superior drought resistance groups indicated that these group members were probably able to extract more available soil water during the drought period. No commercial cultivars were found in the most drought resistance groups. These field studies also suggested that future collections of bermudagrass ecotypes designed to select for drought resistance might best be carried out from regions that experience Mediterranean climates. The field evaluations presented here did not correlate well with drought resistance determined in previously reported shallow lysimeter (40 cm deep) experiments.