Evaluation of Dryland Wheat Cultivars on the Market in South Africa for Resistance against Four Known Russian Wheat Aphid, &amp;lt;i&amp;gt;Diuraphis noxia&amp;lt;/i&amp;gt;, Biotypes in South Africa

Astrid Jankielsohn

doi:10.4236/ae.2019.71001

Abstract

An increased wheat yield potential under changing environmental conditions is a challenge in agriculture. Resistant wheat lines can yield more than susceptible wheat lines in the presence of Russian wheat aphid infestation. There are currently four Russian wheat aphid (RWA) biotypes known in South Africa with different virulence against different wheat cultivars. To keep up with the ever-changing patterns it is necessary to screen the cultivars for resistance against these Russian wheat aphid (RWA) biotypes. All the dryland wheat cultivars on the market were evaluated for resistance against the four known Russian wheat aphid (RWA) biotypes in South Africa. Through this evaluation, the status of Russian wheat aphid (RWA) resistance in South African dryland wheat cultivars can be updated to adapt to environmental changes and the wheat industry can adapt to changes in virulence of Russian wheat aphid (RWA) biotypes that may cause damage to Russian wheat aphid (RWA) resistant cultivars, subsequently affecting yield. Evaluations were done in the glasshouse by screening wheat cultivars against four different South African Russian wheat aphid (RWA) biotypes, RWASA1-RWASA4, under controlled conditions. The glasshouse evaluations showed that out of the 19 dryland wheat cultivars currently on the market in South Africa 16 are resistant against RWASA1, 7 are resistant against RWASA2, 7 are resistant against RWASA3 and 5 are resistant against RWASA4. Dryland wheat cultivars were also evaluated under field conditions at four different field localities. In the field, 5 cultivars were resistant to RWASA3 at two localities, respectively, and 3 and 5 cultivars were resistant to RWASA4 at two localities, respectively. Since Russian wheat aphid (RWA) damage can influence the final yield of a wheat cultivar significantly, changing conditions can influence both resistant cultivars, and the virulence of Russian wheat aphid (RWA). It is advisable to evaluate wheat cultivars on the market under different conditions and with all known Russian wheat aphid (RWA) biotypes in an area.

Highlights

Wheat yield is one of the most important factors to consider by wheat producers and increased yield under changing conditions is a priority in wheat breeding
The status of Russian wheat aphid (RWA) resistance in South African dryland wheat cultivars can be updated to adapt to environmental changes and the wheat industry can adapt to changes in virulence of Russian wheat aphid (RWA) biotypes that may cause damage to Russian wheat aphid (RWA) resistant cultivars, subsequently affecting yield
Lal Hussain Akhtar et al [7] found that Russian wheat aphid infestation caused a significant loss to grain yield in wheat and according to Karren [8], each 1% infestation level of RWA will result in 0.5% yield loss of wheat at harvest

Summary

Introduction

Wheat yield is one of the most important factors to consider by wheat producers and increased yield under changing conditions is a priority in wheat breeding. RWA is widely distributed, the economic impact to small grains occurs predominantly in South Africa, the US and Canada [3]. It is suggested that the most important contributing factor to yield reduction in small grains attacked by RWA is head trapping, resulting from the aphid’s prevention of the unrolling of newly emerging leaves [5] [6]. Current management practices for winter wheat include the use of resistant cultivars, and it is important to ensure that cultivars released in South Africa have sufficient, but more importantly, lasting resistance against the Russian wheat aphid in order to minimize yield losses as far as possible. There are currently four Russian wheat aphid biotypes known in South Africa [11].

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