Physiological Traits Associated with Drought Tolerance in Lantana

Lantana camara L. is a popular ornamental landscape plant that is widely used in the warmer portions of the United States.  In addition to their ornamental value, L. camara is also a lower water use plant.  The development of new cultivars that use water as efficiently as possible is important as a part of a breeding program.  Two groups of maternally related genotypes, including diploid, triploid, tetraploid, pentaploid, and hexaploid lines, were derived from L. camara ‘Gold’ and L. camara ‘Pink Caprice’ and were used in this study.  Additionally, 40 commercially available cultivars were included.  The purpose of this study was to assess the efficacy of several screening methods for value as a selection tool and to examine the relative drought resistance among related genotypes and commercial cultivars.  Xylem water potential, photosynthetic rates, stomatal conductance, tissue and substrate water content at foliage death, days to wilt, and days to foliage death.  Significant differences within the maternally related groups of genotypes were observed for all of the above mentioned parameters.  Similar results were observed among the commercial cultivars.  It appears that ploidy level has little influence on photosynthetic rates or stomatal conductance during drought stress in the genotypes studied.  These results suggest that the inclusion of screening tools like physiological parameters in response to drought stress should allow more water-efficient cultivars to be selected more readily, leading to further breeding advancement and variety recommendation.