Document Type

Thesis - Open Access

Award Date

2018

Degree Name

Master of Science (MS)

Department / School

Agronomy, Horticulture, and Plant Science

First Advisor

Emmanuel Byamukama

Keywords

Flooding, Heterodera glycines types, Reproduction, SCN weed hosts, soybean cyst nematode, Winter annual weeds

Abstract

The soybean cyst nematode (SCN; Heterodera glycines, Ichinohe) is an important pathogen of soybean in South Dakota which causes significant yield losses. SCN has been found in 30 South Dakota counties as on 2017 and is estimated to cause yield loss of 1.9 Metric tons (Mt) annually. SCN has diverse crop and weed hosts as it can reproduce in several crops and weeds. The presence of Heterodera glycines (HG) types can reduce the effectiveness of SCN-resistant cultivars and the HG types reproduction on weed hosts can negate the effectiveness of crop rotation by continued build-up in the field. This study examined the alternative weed hosts of SCN in South Dakota based on field and greenhouse studies. Out of 63 weed species studied, field pennycress and purple deadnettle were determined to be the good hosts whereas white clover, common mallow, shepherd’s purse, Canada thistle and cocklebur were determined to the poor hosts of SCN in South Dakota. This research also investigated the reproduction of three commonly found HG types 0, 2.5.7, and 7 on three major weed hosts of SCN in the United States: purple deadnettle, field pennycress, and henbit relative to a susceptible check, Williams-82, under greenhouse conditions. SCN reproduction was found to be influenced by the type of weed species, HG types and their interaction. SCN reproduction was highest for HG type 2.5.7 (FI = 6.4) followed by HG type 7 (FI = 6.1) and HG type 0 (FI = 5.9). Similarly, among weed species, henbit (Lamium amplexicaule) was found to harbor highest SCN cysts followed by purple deadnettle (Laminum purpureum) (FI = 6.9) and field pennycress (Thalpsi arvense) (FI = 4.8). These results indicate that all the three weeds considerably supported SCN HG types tested and hence these weeds should be managed proactively as an important component of SCN management strategies. Another aspect of this research was to determine the effects of flooding on SCN development with or without nematicide seed treatment. Flooding days and seed treatment affected the number of SCN cysts on the susceptible cultivar. The greatest number of cysts developed when plants were flooded for 2 days (Cyst = 36) followed by treatments flooded for 0, 4, and 6 days. The number of cyst was lowest for the plants flooded for 8 days (Cysts = 26). This study also indicated that ILeVO seed treatment lowered SCN reproduction on a SCN susceptible soybean cultivar and promoted root development. This study indicated that a few weeds support SCN reproduction which is impacted by the presence of different HG types of SCN, flooding and seed treatments. All these aspects should be integrated with other management strategies in order to manage SCN effectively.

Library of Congress Subject Headings

Soybean cyst nematode -- South Dakota.
Soybean cyst nematode -- Control.
Soybean -- Diseases and pests.
Host plants.
Weeds.

Description

Includes bibliographical references

Format

application/pdf

Number of Pages

143

Publisher

South Dakota State University

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Rights Statement

In Copyright