Vertical Distribution of Heterodera schachtii under Susceptible, Resistant, or Tolerant Sugar Beet Cultivars

Abstract

Westphal, A. 2013. Vertical distribution of Heterodera schachtii under susceptible, resistant, or tolerant sugar beet cultivars. Plant Dis. 97:101-106.Heterodera schachtii is managed by rotation with non-hosts, resistant cover crops, and resistant and tolerant sugar beet cultivars. Microplots 60 cm deep and 30 cm in diameter containing steamed field soil were (i) noninfested or infested with 550 H. .schachtii eggs per 100 g at (ii) 0 to 60 cm, (iii) 0 to 30 cm or (iv) 30 to 60 cm in depth. Plots were planted to susceptible, resistant, and tolerant sugar beets. Five weeks later, the sugar beet canopy was largest in condition i, smallest in condition ii, and intermediate in conditions iii and iv. White sugar yield (WSY) was highest in condition i, second in condition iv, lowest in condition ii, and intermediate in condition iii. Cultivar-speeific final nematode numbers were independent of the level of infestation. In two experiments utilizing l-m-microplots, naturally occurring H. schachtii populations were suppressed with fosthiazate at depth layers in reverse to those infested in the first experiment, and planted to susceptible, resistant, and tolerant sugar beets. In one experiment, WSY was highest in soil treated with fosthiazate at 0 to 60 cm in depth, lowest in nontreated, unaffected in soil treated at 30 to 60 cm in depth, and somewhat lower in soil treated at 0 to 30 cm in depth. In all cultivars, early root penetration predicted canopy diameter; only in the susceptible cultivar did the canopy diameter predict WSY. Deep-occurring H. schachtii can impact productivity in sugar beet cropping.

Water use efficiency of sugar beet cultivars (Beta vulgaris L.) susceptible, tolerant or resistant to Heterodera schachtii (Schmidt) in environments with contrasting infestation levels

“…Heijbroek et al (2002) also measured higher sugar yields of resistant cultivars at infested sites compared to a susceptible standard. On the contrary, Westphal (2013) found no differences in white sugar yield between a resistant and susceptible cultivar in microplot experiments with nematodes, but a higher white sugar yield of a tolerant cultivar.…”

“…In most cases a high Pi resulted in a high yield reduction of susceptible cultivars (Griffin, 1988;Jones, 1956;Westphal, 2013). In contrast, Kenter et al (2014) could not confirm this relation in each of their 13 trials and stated that environmental factors beyond Pi must have had strong influence on the yield response to H. schachtii.…”

“…This can lead to severe yield losses in sugar beet (Griffin, 1988;Steudel and Thielemann, 1979;Heijbroek et al, 2002). Three cultivar types (hereafter called cultivars) are available, which are categorized as susceptible, tolerant or resistant to SBCN (Daub and Westphal, 2012), but none of them is protected against nematode invasion as results for example by Westphal (2013) clearly show. Resistance is defined as the ability of a plant to limit nematode reproduction relative to reproduction within a plant lacking such resistance (Müller, 1989;Yu and Steele, 1981).…”

Temporal sampling helps unravel the genetic structure of naturally occurring populations of a phytoparasitic nematode. 2. Separating the relative effects of gene flow and genetic drift

“…In fall 2012, 120 plants were sampled and marked with plastic tags. Due to their small size (<1 mm), active dispersal of H. schachtii individuals occurs over very short spatial distances (Plantard & Porte, ; Wallace, ; Westphal, ). Thus, the soil sampled around the roots of one plant was considered as being one nematode population for subsequent analyses.…”

“…In fall 2012, 120 plants were sampled and marked with plastic tags. Due to their small size (<1 mm), active dispersal of H. schachtii individuals occurs over very short spatial distances (Plantard & Porte, 2004;Wallace, 1968;Westphal, 2013).…”