The relationship between natural rain intensity and Ascochyta blight in chickpea development.

Ihsanul Khaliq,Adam H Sparks,Kevin Moore

doi:10.31220/agrirxiv.2021.00063

Ihsanul Khaliq, Adam H Sparks + Show 1 more

Open Access

https://doi.org/10.31220/agrirxiv.2021.00063

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Abstract

Abstract Ascochyta blight is one of the most devastating diseases of chickpea worldwide. In Australia, Ascochyta blight management strategy in a standing crop is solely based on applying protective fungicides before a forecast rainfall event. Despite this, studies on the likely interaction between variable natural rain amount, rain duration, environmental factors and Ascochyta blight development are rare. We used generalised linear mixed models to investigate the relationship between rain intensity, wind speed and Ascochyta blight development. Briefly, 7 g of infested chickpea residue were placed at the soil surface in a 1 m 2 plot, and three pots (3 trap plants per pot) of a susceptible chickpea cultivar were randomly placed on each side of the 1 m 2 plot (total 12 pots), preceding a forecast rainfall event. Trap plants were transferred to a controlled temperature room (20°C) for 48 h (100% humidity) after rain events. After a 48 h incubation period, trap plants were transferred to a glasshouse (20°C) to allow lesion development. The number of lesions on all plant parts were counted after two weeks. Lesions developed in rain amounts as low as 1.4 mm and rain durations as short as 0.7 h. The number of lesions significantly increased with increasing rain amount. There was positive effect of increasing rain duration and a negative effect of increasing wind speed. This study suggests that small rain amounts, shorter duration rains or a limited amount of primary inoculum are not barriers to conidial dispersal or infection.

Highlights

Chickpea (Cicer arietinum) is the second most important crop globally with the production value of more than $7.6 B between 2014–2016 (FAOSTAT, 2018)
Lesions were recorded on trap plants in rain amounts as low as 0.8 mm (Khaliq et al, 2020)
To the best of our knowledge, this study is the first to investigate the effect of natural rain intensity and intrinsic attributes associated with rain on Ascochyta blight in chickpea development

Summary

Introduction

Chickpea (Cicer arietinum) is the second most important crop globally with the production value of more than $7.6 B between 2014–2016 (FAOSTAT, 2018). Phoma rabiei) is the major biotic constraint to chickpea production worldwide (Pande et al, 2005, Nene, 1982). Yield losses from Ascochyta blight can be up to 100% in susceptible cultivars under favourable conditions (Nene, 1982). Ascochyta rabiei is known to survive on infested residue, infected seed and volunteer chickpea plants (Pande et al, 2005). Infested residue and volunteer chickpea plants serve as the main source of inoculum for disease initiation, and even less than 1 % infested residue can result in serious yield losses under conducive conditions (Kaiser, 1992). Infection and disease development are favoured by temperatures between 10–30 °C with optimum 20 °C (Kaiser, 1973), relative humidity > 95 % (Nene, 1982), and wetness period of at least 6–10 h (Moore et al, 2016). There is no resistant variety available against Ascochyta blight in Australia. All varieties are susceptible to moderately susceptible (https://www.nvtonline.com.au/)

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