Assessment of low light tolerance of seashore paspalum and bermudagrass

Low light (LL) stress is a major problem that influences turfgrass quality. Low light tolerance of seashore paspalum (Paspalum vaginatum Swartz) has not been assessed and information is needed to develop management strategies and to maximize turf performance. The objectives of this study were to: (i) evaluate responses of seashore paspalum to reduced light intensity and to identify the most tolerant entries; (ii) compare low light responses between paspalum and hybrid bermudagrass (Cynodon dactylon L. x C. transvaalensis Burtt Davy) cultivars. Eight entries of seashore paspalum and two hybrid bermudagrass cultivars were evaluated under full sunlight control (FL), and constant 70% and 90% LL provided by shade shelters in the field from August to October in 2001 and July to September in 2002 at Griffin, GA. Significant differences in turf quality, color, density, canopy photosynthetic rate (Pn), canopy chlorophyll index (Chl), canopy spectral reflectance, and leaf dry weight were observed in paspalum entries and hybrid bermudagrass cultivars under 70 and 90% LL treatments. Among all grasses, turf quality declined 9 (the best) to 22% (the worst) under 70% LL and 13 to 28% under 90% LL, respectively, compared with the control with FL. Canopy photosynthetic rate was reduced 10 to 43% under 70% LL and 27 to 67% under 90% LL; and normalized difference vegetation index (NDVI) decreased 14 to 31% and 20 to 45% for 70% LL and 90% LL treatments, respectively. Most paspalum entries exhibited better low light tolerance than hybrid bermudagrasses under 70 and 90% LL, and 'Sea Isle 1' paspalum ranked as the most tolerant cultivar under both LL conditions. The ranking for the most low light tolerant entries under two LL conditions were: 'Sea Isle 1' paspalum (best) > Cloister paspalum = 'Sea Isle 2000' paspalum > Temple 1 paspalum = 'Salam' paspalum > Q 36313 paspalum = 561-79 paspalum = Hybrid 5 paspalum > 'TifSport' bermudagrass = 'TifEagle' bermudagrass (worst). Large variations observed among paspalum entries and bermudagrass cultivars in response to LL conditions could potentially be used for enhancing management practices.