Damage thresholds and population dynamics of Meloidogyne chitwoodi on carrot (Daucus carota) at different seed densities

Abstract

Yield loss of carrot (Daucus carota) cv. Nerac caused by Meloidogyne chitwoodi and population dynamics of this nematode were studied using a range of 13 nematode densities at three seed densities (2, 4, 18 seeds pot −1 ) in a climate-controlled glasshouse. Yield and quality data were fitted to Seinhorst's yield models. Final population densities were fitted to the population dynamic models for sedentary and free-living nematodes. The tolerance limits for yield loss were 0.34, 0.62 and 0.50, while that of quality were 0.012, 0.142 and 0.813 second-stage juveniles (J2) (g dry soil) −1 at increasing seed densities, respectively. The minimum yield (m), increased with seed density: 0.25, 0.30 and 0.50; the minimum quality yield was 0.10, 0.08 and 0.15 J2 (g dry soil) −1 at increasing seed densities, respectively. Both maximum multiplication rates and maximum population densities increased with increasing seed density but were generally low. Carrot cv. Nerac can be considered a bad host for M. chitwoodi.

Damage thresholds and population dynamics of Pratylenchus penetrans on carrot (Daucus carota L. cv. Nerac) at three different seed densities

“…Establishment of cv. Nerac into carrot plant was reported to be independent of seed density and Pi of M. chitwoodi, but carrot plants that developed carrot taproots were negatively correlated with Pi at the same seed densities (Heve et al 2015). The negative correlation between carrot taproot length and diameter with the Pi, confirms previous results from Coosemans (1975) and Vrain and Belair (1981).…”

“…In order to synchronise the germination of the carrot seeds with the inoculation of the nematodes into the soil, seeds were soaked in water for 4 days prior to planting. The detailed procedure is described in Heve et al (2015). After inoculation, each pot was sown with either 2, 4 or 18 seeds pot −1 to obtain an equivalent seed density of 1, 2 and 10 million ha…”

“…Carrot seeds were planted at 5 mm depth. To make sure that the required numbers of plants per pot of 2, 4 and 18 seeds were obtained, 2, 4 and 4 extra seeds per seed density were added, respectively, based on a 94 % germination rate reported by Heve et al (2015) for cv. Nerac.…”

“…Moreover, the increase in weight due to plant growth was taken into consideration during watering (1 ml extra water for each g of growth based on prior studies for cv. Nerac (Heve et al 2015). Plants were fertilized weekly with 0.3 % WUXAL® Super liquid foliar fertilizer (Agrarverstand Oberland, Schongau, Germany).…”

“…Plants were fertilized weekly with 0.3 % WUXAL® Super liquid foliar fertilizer (Agrarverstand Oberland, Schongau, Germany). On account of the growth pattern described in Heve et al (2015), carrots were harvested 83 days after germination when they reached the industry desired diameter of the carrot taproot.…”