Abstract
Field experiments testing rates of various nematicides, with and without NPZn fertiliser, were analysed to investigate how root-lesion nematode (Pratylenchus thornei) affects growth and yield components of susceptible/intolerant wheat cultivars in a subtropical environment. Plant response to nematode attack was assessed by regression and principal components analyses of various plant parameters at different crop development stages, in relation to different nematode population densities in the roots and root-zone soil. Reduction in P. thornei population densities by nematicides resulted in increased numbers of tillers, plant biomass, N and P concentrations and uptakes, numbers of spikes and kernels, and grain yield. Grain yield was strongly correlated with number of kernels, biomass and number of spikes, and negatively correlated with number of P. thornei in the root-zone soil at stem elongation. This study showed that P. thornei damage to roots decreased wheat yield through limiting N and P concentrations and uptakes in plant tops causing poor growth that commenced early and continued through the life of the crop. Genetic, environmental and management factors that reduce population densities of P. thornei, and decrease the impact of the nematodes starting in early crop growth, will greatly increase spike and kernel numbers and grain yield.
Highlights
Root-lesion nematodes (Pratylenchus spp.) infest roots of many plant species, and globally they constitute the third most economically important nematode group after cyst (Heterodera spp. and Globodera spp.) and root-knot nematodes (Meloidogyne spp.) [1,2]
Cultivar ratings are presented for growers in nine ordinal categories from resistant (R) to very susceptible (VS) based on data for final population densities of P. thornei from experiments combined by multi-environment trial (MET) analysis [11]
Cultivar ratings are presented for growers in nine ordinal categories from tolerant (T) to very intolerant (VI) based on data for grain yield over sites and years combined by MET analysis [12]
Summary
Root-lesion nematodes (Pratylenchus spp.) infest roots of many plant species, and globally they constitute the third most economically important nematode group after cyst (Heterodera spp. and Globodera spp.) and root-knot nematodes (Meloidogyne spp.) [1,2]. Cultivar ratings are presented for growers in nine ordinal categories from tolerant (T) to very intolerant (VI) based on data for grain yield over sites and years combined by MET analysis [12] Grain production in this region is mainly on dark cracking clay soils known as vertisols [13], because they have high plant-available water capacity. The results provide new information on the impact of the nematodes on uptake of N and P by young wheat plants and effects on the subsequent wheat growth and components of grain yield This information is valuable (a) for designing strategies for integrated management of P. thornei on farms, (b) for modifying crop growth models in order to simulate the effects of P. thornei on wheat production in this environment, and (c) for guidance in assessing next-generation nematicides [17,18,19] for potential responses in wheat under field conditions appropriate to the region
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