The progress of the project will be evaluated by monitoring the number of SCN genes found associated with SCN hatch potential and the number of SCN populations collected from growers and tested for SCN hatch potential using the molecular assay. We expect to finish the proposed project in a year (October 1, 2022 to September 30, 2023). The aim 1 will take about five months, from October 2022 to February 2023. The aim 2 will be conducted the following seven months, from March to September of 2023.
Aim 1:
The status of SCN hatch potential as a trait of SCN is determined by differently expressed nematode genes in response to temperature and availability of host roots. We aim to identifying SCN genes responsible for SCN hatch potential by analysis of gene expression using RNA-sequencing (RNA-seq) on SCN eggs treated with low temperature (4oC) or exposed to soybean root exudates. RNA-seq is a nextgeneration sequencing technique commonly used to identify genes potentially involved in a specific biological process (Wang et al., 2009). We will determine SCN genes highly expressed in active SCN eggs stimulated by soybean root exudates or low temperature-induced dormant eggs. We expect to select at least 20 SCN genes as candidate marker genes of nematode hatch potential. The SCN candidate genes
selected here will be tested using SCN populations from soybean fields in Aim 2.
Aim 2:
We will contact at least 50 soybean growers in Indiana in the spring of 2023 who previously submitted soil samples to us in 2020 and 2021 to get more soil samples on fields where the previous crop is soybean. The eggs of SCN populations will be isolated from the soil samples, and egg numbers will be counted and returned to growers free-of-charge. We plan to implement a molecular diagnostic assay to evaluate hatch potentials of the 50 SCN populations using quantitative PCR (qPCR) by measuring expression of the 20 candidate SCN marker genes selected in Aim 1. In the meantime, the traditional SCN hatch assay will be performed on the SCN populations. We will set up the traditional hatch assay in lab and monitor hatch of SCN eggs in a 3-week-period to determine the hatch rate of a SCN population. Statistical association studies between the molecular assay and regular SCN hatch assay will be conducted to narrow down to 2 to 3 nematode genes that are able to serve as reliable markers of SCN hatch potential. We will notify growers about the SCN hatch potentials and summarize the data to develop a fast and reliable molecular assay to evaluate hatch potential of SCN populations. The molecular diagnostic assay for SCN hatch potential developed here can be completed within 8 hours and less expressive in comparison to the three-week time needed by a regular SCN hatch assay.