Document Type

Thesis - Open Access

Award Date

2016

Degree Name

Master of Science (MS)

Department

Plant Science

First Advisor

Emmanuel Byamukama

Abstract

The soybean cyst nematode (SCN), Heterodera glycines Ichinohe, is an endoparasitic nematode and one of the major pests of soybean (Glycine max L.) in the United State and all over the world where soybean is grown. SCN is ranked first among the biological factors that cause yield loss in soybean. The estimated yield loss by this nematode is $1b annually in the United States alone. SCN is thought to have been first found in China. It was first identified in the United States in 1954 in North Carolina and in South Dakota in 1995. To date, SCN continues to spread in South Dakota having been detected in 29 counties. SCN is spread through soil movement when the soil is infested with SCN. The females (cyst) and also eggs remaining outside the cyst are the dispersal units of SCN. The second stage juveniles (J2) (worm-like, infecting stage) hatch from the eggs after stimulation from soybean roots, and infects the soybean roots. SCN not only attacks soybean, but also invades several other leguminous crops such as common bean (Phaseolus vulgaris L.), black bean (Phaseolus vulgaris L.), kidney bean (Phaseolus vulgaris L.), pinto (Phaseolus vulgaris L.) and navy (Phaseolus vulgaris L.) and forage legumes such as vetch (Vicia sativa), lespedeza (Kummerowia sp.), and lupine (Lupinus perennis). Several winter weeds like common chickweed (Stellaria media), henbit (Lamium amplexicaule), purple deadnettle (Lamium purpureum), small-flowered bitter cress (Cardamine hirsuta), shepherd’s-purse (Capsella bursa-pastoris), and field pennycress (Thlaspi arvense) are also hosts for SCN. The losses to soybean production caused by SCN vary mainly with the degree of infestation (population density), susceptibility of the cultivar grown, and other biotic and abiotic factors such as soil type and weather conditions. SCN can cause yield loss of up to 30 % without showing any visible symptoms in the plants and losses can go up to 75% in heavily infested fields. SCN completes its life cycle within 3 to 4 weeks depending upon the environmental factors mainly soil temperature. SCN population genetic diversity is the most challenging aspect for the management of this nematode. This study examined the distribution of Heterodera glycines and characterized HG types prevalent in South Dakota by monitoring the present status, population density, and determining HG types. This study also assessed the resistance of few of the available commercial soybean cultivars against prevalent HG types occur in South Dakota. A total of 250 soil samples were arbitrarily collected from different counties of South Dakota that had previously been found positive for SCN. Analysis of the soil samples showed a high prevalence of SCN infestation (32%) of the soil samples collected for this study and SCN population density varied from 250 to 62,500 per 100 cm3 of soil. The extracted SCN populations were subjected to HG type determination under greenhouse conditions. A total of eight types of Heterodera glycines population were found in South Dakota. Among the eight HG types, HG types 0, 2.5.7, and 7, were most prevalent. Assessment of commercial cultivars for resistance showed varied reaction from susceptible to resistant. Most of the commercial soybean cultivars tested were resistant to HG type 0 and moderately resistant to HG type 0, 2.5.7, and 7 and only one cultivar showed susceptibility to all three populations tested in greenhouses conditions. These results indicate that host resistance is effective in managing in SCN in South Dakota. However, with almost all SCN resistant cultivars having similar source of SCN resistance genes (PI 88788), and some populations of SCN having > 10% reproduction on PI 88788, there is a need to integrate host resistance with crop rotation, nematicide seed treatments, and rotation within resistant cultivars for sustainable SCN management in South Dakota.

Library of Congress Subject Headings

Soybean cyst nematode -- South Dakota

Soybean -- Diseases and pests

Description

Includes bibliographical references

Format

application/pdf

Number of Pages

117

Publisher

South Dakota State University

Rights

Copyright © 2016 Krishna Acharya

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