Theses and Dissertations

Issuing Body

Mississippi State University


Klink, Vincent

Committee Member

Lawrence, Gary W.

Committee Member

Gordon, Donna M.

Committee Member

Li, Jiaxu

Date of Degree


Document Type

Dissertation - Open Access


Biological Sciences

Degree Name

Doctor of Philosophy


College of Arts and Sciences


Department of Biological Sciences


Plant-parasitic nematodes are the cause of devastating yield loss in vital agricultural crops around the world. Heterodera glycines, also referred to as soybean cyst nematode, is the main pathogen of Glycine max (soybean) causing more loss than all other pathogens of G. max combined. The resultant economic impact due to H. glycines in United States soybean production alone is estimated to account for an annual one-billion-dollar loss. Natural resistant genotypes have been found in trials to combat this pathogen. Of the resistant varieties identified, G. max[Peking/PI 548402] and G. max[PI 88788] are the major sources of resistance. Identification of genes expressed in the cells of which the nematode parasitizes, the syncytia, exclusively undergoing the resistant/incompatible reaction from the two major sources of resistance mentioned previously have identified a number of candidate genes presumed to function in defense to H. glycines parasitism. Prior to this work, success has been obtained by selection of a number of these candidate genes in functional analysis to show involvement in defense. This work is aimed at functionally identifying signaling components involved in the defense reaction. Reverse genetic studies of NON-RACE SPECIFIC DISEASE RESISTANCE 1 Glycine max homolog, Gm-NDR1-1, has confirmed a functional role in the defense to H. glycines to G. max. Gene expression studies revealed both effector-triggered immunity (ETI) and pattern-triggered immunity (PTI) components to be regulated by Gm-NDR1-1. Furthermore, induction in the heterologous expression of Gm-NDR1-1 in Gossypium hirsutum (cotton) suppressed Meloidogyne incognita parasitism. Harpin treatment has been evaluated due to the knowledge of NDR1’s capability of being harpin-induced (HIN1). Expression studies of the harpin treatment did in fact induce Gm-NDR1-1. The analysis further provides evidence of NDR1 role in defense by displaying the harpin-induced response of NDR1 in resistance to infection of Rotylenchulus reniformis. Receptors are known to function through signaling components in plant defense. Therefore, the conserved downstream signaling component of multiple diverse stimuli, mitogen-activated protein kinases (MAPKs) were functionally characterized in G. max for their role in resistance to H. glycines via the reverse genetic parasitism assays and evaluated to observe the effect on defense gene expression.