Wheat biomass and yield increased when populations of the root-lesion nematode (Pratylenchus thornei) were reduced through sequential rotation of partially resistant winter and summer crops

Abstract

The root-lesion nematode, Pratylenchus thornei, can reduce wheat yields by >50%. Although this nematode has a broad host range, crop rotation can be an effective tool for its management if the host status of crops and cultivars is known. The summer crops grown in the northern grain region of Australia are poorly characterised for their resistance to P. thornei and their role in crop sequencing to improve wheat yields. In a 4-year field experiment, we prepared plots with high or low populations of P. thornei by growing susceptible wheat or partially resistant canaryseed (Phalaris canariensis); after an 11-month, weed-free fallow, several cultivars of eight summer crops were grown. Following another 15-month, weed-free fallow, P. thornei-intolerant wheat cv. Strzelecki was grown. Populations of P. thornei were determined to 150 cm soil depth throughout the experiment. When two partially resistant crops were grown in succession, e.g. canaryseed followed by panicum (Setaria italica), P. thornei populations were <739/kg soil and subsequent wheat yields were 3245 kg/ha. In contrast, after two susceptible crops, e.g. wheat followed by soybean, P. thornei populations were 10 850/kg soil and subsequent wheat yields were just 1383 kg/ha. Regression analysis showed a linear, negative response of wheat biomass and grain yield with increasing P. thornei populations and a predicted loss of 77% for biomass and 62% for grain yield. The best predictor of wheat yield loss was P. thornei populations at 0–90 cm soil depth. Crop rotation can be used to reduce P. thornei populations and increase wheat yield, with greatest gains being made following two partially resistant crops grown sequentially.

Tolerance of wheat cultivars to root‐lesion nematode (Pratylenchus thornei) assessed by normalised difference vegetation index is predictive of grain yield

“…These relationships were still evident at the low population densities for Experiments 1 and 2 (2,570 and 975 P. thornei /kg soil) but not so for Experiment 3 (578 P. thornei /kg soil). These results are in line with previously established thresholds for grain yield loss taken to be 2,000 P. thornei /kg soil at any depth interval in the soil profile (Thompson et al, ) or 1,000 P. thornei /kg soil averaged over a soil profile of 0.9 m depth (derived from Figure b; Owen et al, ).…”

“…This pest has forced many growers to grow tolerant wheat ( Triticum aestivum ) cultivars to minimise potential yield losses which can be up to 70% (Thompson, Brennan, Clewett, Sheedy, & Seymour, ). Correct diagnoses of nematode populations, the use of tolerant wheat cultivars and rotations with resistant crops (Owen, Clewett, Bell, & Thompson, ) have reduced the impact of P. thornei from a potential loss of AUD$104 million/year to an actual loss of $38 million/year (Murray & Brennan, ). Continued research and development is required to further reduce yield loss.…”

Survival of root-lesion nematodes (Pratylenchus thornei) after wheat growth in a vertisol is influenced by rate of progressive soil desiccation

“…thornei population densities in the topsoil after wheat maturity and to the pattern of soil profile distributions of P . thornei in some fallow fields where maximum population densities can occur in the subsoil layers at various depths to 60 cm (Thompson et al , ; Owen et al , ). Wilson et al () showed that the rate of evaporation of soil water at high initial contents equalled the potential evaporation from a free water surface for all three soils studied (namely a sand, a silt and a clay soil).…”

Resistance of Wheat Genotypes to Root-Lesion Nematode (Pratylenchus thornei) Can be Used to Predict Final Nematode Population Densities, Crop Greenness, and Grain Yield in the Field

“…Other hosts of P. thornei among crop species grown in this region include winter crops barley, triticale (×Triticosecale), durum (Triticum turgidum ssp. durum), and faba bean (Vicia faba), and summer crops mung bean, black gram (Vigna mungo) and soybean (Glycine max) (Owen et al, 2012(Owen et al, , 2014. Management of P. thornei for wheat production depends on crop sequences that include moderately resistant crop species like sorghum (Thompson et al, 2008(Thompson et al, , 2012aOwen et al, 2014), which is the major summer crop species in the subtropical grain region of Australia.…”

“…Fixed rotations are difficult to implement due to variable rainfall patterns in this region, and flexible crop sequencing (termed opportunity cropping) is often practiced. Pratylenchus thornei survives well in the clay soils of the region and, following growth of a susceptible wheat cultivar, ~3 years of fallow and/or resistant rotational crops are needed to reduce high nematode population densities to below the threshold for damage (Owen et al, 2014;Whish et al, 2017) which is ~2,000 nematodes/kg soil for intolerant wheat cultivars (Thompson et al, 2008). Protection of the major at-risk crops through breeding resistant and tolerant genotypes is essential for the long-term management of P. thornei in this region.…”