Pigeonpea has the potential to offer Queensland growers a new pulse crop to diversify crop choices and therefore and expand economic gains for the grain-growing industry. Pigeonpea provides a valuable source of plant protein and is drought tolerant. Recently, a promising collection of 20 lines of pigeonpea were selected from multiple tests over several sites and years. However, there is no information of the response of this collection to two of Queensland’s most important and widespread soilborne biotic constraints:
- the root-lesion nematode, Pratylenchus thornei
- arbuscular mycorrhizal fungi (AMF).
Pratylenchus thornei is found in 75% of southern Queensland’s grain-producing paddocks. The nematodes can cause yield loss of 65% in wheat and 20% in chickpea and mungbean costing northern region growers $38 million in lost income for wheat alone. To reduce the effect of P. thornei, several resistant crops need to be grown consecutively in crop sequences. However, the nematodes have a broad host range: most cereals and all pulse crops grown in Queensland are susceptible and cause nematode populations to increase.
Queensland’s grain growers need new cropping options, to decrease the effect of these nematodes and to optimise the benefits offered by pulse crops in farming systems.
Previous experiments by Owen et al. (2000) showed that four, older, commercial pigeon pea varieties were resistant and tolerant to P. thornei. In contrast, in 2016 at the Leslie Research Facility, Revell et al. (UQ) found that nine pigeonpea lines were moderately susceptible to P. thornei but plant growth and nematode reproduction was generally poor. The new collection of pigeonpea lines earmarked for release requires characterisation to determine the response of the lines to P. thornei.
Arbuscular mycorrhizal fungi (AMF) are a valuable, but often under-utilised resource in Queensland’s farms. They are beneficial fungi, which colonise the roots of many important Queensland crops such as sorghum and chickpea, and improve:
- the uptake of nutrients such as nitrogen, zinc and phosphorus;
- drought tolerance and,
- plant growth and yield.
Pigeonpea is highly dependent on AMF for plant growth and uptake of phosphorus (Wellings et al. 1991; Thompson 1999). In a glasshouse experiment at UniSQ in 2021 (Owen), pigeonpea plants were 23% larger when AMF were added to pasteurised soil compared soil with no added AMF. Potentially, there may be an interaction between P. thornei and AMF because both organisms occupy the same region within plant roots, which may affect nematode reproduction. Recently, a new method was developed to investigate the interaction of a range of combinations of AMF and P. thornei levels on the growth of mungbean in a field experiment (Owen et al 2021). Remarkably, there were unique responses of each cultivar tested, which changed with the various combinations of AMF and P. thornei. This type of experiment applied to pigeonpea will offer additional insights to interactions that can occur between AMF and P. thornei and their effect on plant growth.
In order to reduce the impact of P. thornei and promote the benefits of AMF in sustainable rain-fed crop production in Queensland, careful planning of crop sequences is required. Pigeonpea potentially offers a new defence in the management of P. thornei, and an opportunity to promote and conserve the benefits offered by AMF to farming systems. The improved uptake of soil nutrients in mycorrhizal plants can also enhance the nutritional quality of grains for human consumption, reduce fertiliser use and increase the availability of poorly mobile nutrients such as phosphorus and zinc.
This project aims to determine the resistance/susceptibility of a promising collection of pigeonpea lines to the root-lesion nematode, Pratylenchus thornei and the effect and potential interaction with beneficial arbuscular mycorrhizal fungi (AMF).
The information generated will:
- optimise glasshouse screening methods for pigeonpea,
- identify if new pigeonpea germplasm has resistance to P. thornei,
- provide a field demonstration of the interaction of AMF x P. thornei.
Results of the project will provide Queensland growers with information about the role of pigeonpea in the management of the root-lesion nematode, Pratylenchus thornei and the importance of AMF to improve uptake of soil water and nutrients, and therefore crop production.