The Effects of Fungicide and Genetics on Fungal Diseases on Wheat in Nebraska with Emphasis on Stem Rust

Authors

Javed Sidiqi, University of Nebraska-LincolnFollow

First Advisor

P. Stephen Baenziger

Second Advisor

Stephen Wegulo

Date of this Version

7-2018

Document Type

Dissertation

Comments

A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Agronomy (Plant Breeding and Genetics), Under the Supervision of Professors P. Stephen Baenziger and Stephen Wegulo. Lincoln, Nebraska: July, 2018

Copyright © 2018 Javed Sidiqi

Abstract

Foliar fungal diseases of wheat (Triticum aestivum L.) pose a serious threat to wheat production. Despite the significant progress that has been made limiting major fungal diseases by developing resistant cultivars, these diseases challenge the economic sustainability of wheat production. The objectives of this research were (1) To determine the effect of fungal plant pathogens on grain yield in eastern NE, released and pre-release winter wheat genotypes were studied in fungicide treated and untreated plots from 2015 to 2017. (2) To determine if Sr7b is present using allelism tests in ‘Gage’ wheat as previously hypothesized.

Sixty genotypes were planted across four environments in fungicide treated and untreated plots. Averaged over the environments and genotypes in three years, the fungicide treated lines yielded (4,496 kg/ ha^-1) 43% more than the untreated lines (3,147 kg/ ha^-1) indicating severe foliar disease. Fungicides contributed to the improvement of protein concentration from 153 (g kg^-1) in untreated plots to 164 (g kg^-1) in the treated plots, and grain test weight was improved from 73 to 77 (kg hL^-1) in the three environments where they were measured.

To determine if Sr7b was present in Gage, Gage was crossed by ISr7b-Ra. F₂ and F_2:3 families were evaluated for stem rust resistance. The segregation of F₂ plants and F_2:3 families for stem rust resistance fitted well with 15:1 ratio for two separate resistance genes in the two replications. These results suggest that Sr7b segregates independently from an unknown resistance gene in Gage.