PAA names 2025 graduate student award winners

In 2000, an endowment was established to honor the late Frank L Haynes, long time professor of potato breeding and genetics at North Carolina State University. 

The PAA held its annual meeting July 27-31 this year in Madison, WI.  This year, we presented awards for five oral presentations and one poster presentation. Below are the awardees and information about their research.

Olee Hoi Ying Lam (first place)

Research: The global human population is projected to approach ten billion by mid-century, which means demand for staple foods like potatoes will continue growing. At the same time, globalization and climate variability are making crops more vulnerable to new and shifting diseases, creating dynamics that challenge traditional scouting and management practices. These evolving pressures raise the need for precision agriculture tools that can find disease quickly and accurately, before it spreads.  

In this project, we employed advanced sensing technology to detect early blight at its earliest infection stage, when a grower’s intervention has the biggest payoff. Using hyperspectral imagery, a sensor that captures light reflectance beyond human vision, we detected subtle crop stress signals in potato leaves before visual symptoms became apparent.

Three years of aerial hyperspectral images (400 – 2500 nm) were acquired at about 850 ft above ground level at an agricultural research station at Hancock, Wisconsin, before row closure, i.e., the timing at which potatoes become susceptible to early blight in Wisconsin. In addition, we collected visually rated disease-onset scores, providing us with a reliable benchmark.

Due to the inherently high-dimensional nature of the hyperspectral data, we performed a feature selection analysis to identify which parts of the light spectrum mattered most for spotting early infected potatoes. The results showed that the important regions were concentrated in the shortwave infrared (SWIR) and red edge regions. These bands capture variation in plant internal structure, defensive compound concentration, and photosynthetic efficiency, which are known to be early signs of infection invisible to the human eyes.

Using these selected SWIR and red edge bands, the machine learning model (random forest) achieved over 90 % accuracy in differentiating healthy and mildly infected plants, even when symptoms were barely visible and hidden in the lower canopy, where human scouts often might miss from above.

These results demonstrate that hyperspectral imaging, coupled with targeted feature selection, can serve as a reliable early warning system for early blight. For growers, this approach could potentially provide a practical decision‑support tool for site‑specific fungicide applications, reducing unnecessary chemical use while safeguarding the rapidly growing global food supply.

Sabina Budhathoki (second place)

Research: Florida potatoes are especially valuable as a winter or early spring crop that contributes to the U.S. supply. However, plant pathogens such as plant-parasitic nematodes (PPNs) threatens their yield.  Sting and stubby-root nematodes are the major PPNs of concern in the state. There are limited nematode management options in this area and majority of growers rely on chemical nematicides. Cover cropping is a cultural practice that can manage PPNs and impact beneficial free-living nematodes. 

The objective of my project was to evaluate summer and fall cover crops for managing sting and stubby-root nematodes and their effects on free-living nematodes. We conducted repeated field trials to test summer cover crops; sunn hemp and sorghum-sudangrass followed by fall brassica cover crops; arugula and caliente mustard in winter before potatoes were planted. These cover crops were compared with nematicide 1,3-Dichloropropene (1,3-D) application and weedy fallow for their efficacy on nematode abundances. 

Our findings revealed that sunn hemp generally suppressed sting nematode population indicating its promise to use in rotation with potato, although its effect on stubby-root suppression was inconsistent. On the other hand, brassica crops; arugula or caliente increased these nematode abundances, therefore maybe not effective in managing either sting or stubby-root nematode. 1,3- D fumigation provided the most sting nematode suppression. Sunn hemp also improved the marketable yield of potato in first year of study while arugula and caliente mustard reduced their yield. Summer cover crops did not affect free-living nematodes. Arugula and caliente mustard had inconsistent effects on free-living nematodes, but 1,3-D fumigation tended to reduce their population.

Sophie Verkoulen (third place)

Research: Invasive pests can pose great risks to crop productivity, potentially harming the agriculture economy, as well as posing threats to food security. Due to its ability to rapidly adapt to insecticides, the Colorado potato beetle (CPB), Leptinotarsa decemlineata, continues to be a destructive hindrance to potato production that warrants further research. As CPB adapts to both organic and conventional insecticides, researchers have been searching for new avenues for pest control, particularly in the sphere of bio-pesticides. One of these novel bio-pesticides, Calantha, uses the mechanism of RNA interference (RNAi) through double stranded RNA (dsRNA) ingestion to control CPB populations. 

This study aims to characterize neuropeptides and their receptors in CPB, in hopes that neuropeptides could serve as the target of interest in a new generation of insecticides. Neuropeptides are signaling proteins in the central nervous system that regulate important physiological processes and, as a field, are relatively under-explored in CPB. Using quantitative PCR, gene expression of five neuropeptides and one suspected neuropeptide receptor were compared for differentiation over life stages, sexes, and tissues. Due to their tissue specificity and high expression in the larval stages, the neuropeptide GPA2 and its receptor LGR1 were chosen as targets of RNAi trials to observe the phenotypic effects their knockdown has on CPB survival. 

RNAi is a process of gene silencing whereby dsRNA is introduced into an organism effectively blocking protein translation of a specific gene. RNAi can occur endogenously within organisms, but in this study, it is triggered through the introduction of exogenous dsRNA. Introduction of dsRNA was carried out via both injection and feeding mechanisms to 4th instar CPB larvae. Daily assessments were conducted on the experimental larvae, including measurements of weight, percent defoliation, time in life stage, and survivorship. 

Preliminary observations in the feeding trial showed a significant reduction in the weight of CPB larvae that underwent LGR1 RNAi knockdown compared to the untreated control larvae. This could potentially be tied to the upregulation of the LGR1 gene in both larvae and adult midgut samples. Further investigation into percent defoliation, time in life stage, and survivorship, as well as RNAi knockdown trials on the other four neuropeptide targets will help to broaden and define this research more clearly. 

Morgan Weissner (fourth place)

Research: The Colorado potato beetle (CPB), Leptinotarsa decemlineata, is a notorious, global pest that can quickly develop resistance against a wide range of insecticides due to their enhanced detoxification mechanisms. This ability to adapt threatens the sustainability of integrated pest management programs and highlights the need for novel, targeted control strategies. 

One new approach utilizes the naturally occurring RNA interference (RNAi) pathway within the beetle through foliar applications of double-stranded RNA. Specifically, ledprona, the active ingredient in the biopesticide Calantha™, targets and silences an essential gene found only in CPB, which ultimately leads to death. While Calantha is a highly specific control method, there is value in investigating the potential for sublethal impacts of utilizing RNAi for such an adaptive pest. Under field-relevant conditions, insect pests are exposed to varying doses of insecticides due to product degradation or incomplete spray coverage, leading to sublethal exposures within a field where the organisms continue to survive and reproduce. Exposure to sublethal doses of toxins is already known to produce numerous phenotypic responses in insects, but sublethal effects of RNAi technologies, and their potential for carry-over effects, remain understudied.

Preliminary investigations within our laboratory established sublethal doses of ledprona in lab-reared CPB by assessing the no observable effect limits. Sublethally exposed beetles were then monitored throughout their development and allowed to mate and reproduce. Reproductive and developmental consequences of sublethal exposure to insecticides were measured. To assess the potential for inheritance of sublethal effects, this study focused on the offspring of these treated beetles and monitored phenotypic responses throughout their development. Measured responses include survival, development rate, larval and adult weights, and pupation success. 

Understanding how exposed pests and their offspring behave and perform at sublethal levels is critical for predicting real-world outcomes and refining RNAi-based pest management strategies. Our results help inform potato growers on the efficacy and long-term sustainability of novel RNAi technologies on CPB.

Joseph Ifeanyi Ulasi (fifth place)

Research: Late blight, caused by the oomycete Phytophthora infestans, remains one of the most devastating and economically significant diseases of potato (Solanum tuberosum), leading to severe yield losses worldwide. Natural resistance (R) genes present in wild potato relatives are critical for achieving durable resistance, yet their use in breeding has been hindered by reproductive barriers with cultivated potato.

This research aims to introgress and pyramid novel late blight R-genes from wild species, Solanum pinnatisectum, Solanum venturii, and Solanum microdontum with other late blight R genes in Michigan State University potato breeding program into cultivated diploid potato breeding lines. Using molecular markers, two S. pinnatisectum accessions (PI275232 and PI275233) were screened for Rpi-blb3 and the novel Rpi2 genes, while the breeding line MSKK1819, with S. venturii background, was screened for Rpi-vnt1. Three individuals (PI275232-6a, -8a, -9a) tested positive for Rpi-blb3 DNA marker, and four individuals from PI275233 (PI275233-1, -5, -7, -10) tested positive for Rpi2 DNA marker. Additionally, three individuals (MSKK1819-1, -4, -7) were DNA marker-positive for Rpi-vnt1. These lines have been evaluated for foliar resistance using detached leaf assays (DLA) with two P. infestans strains: US-23 and NL13316. PI275233 lines showed complete resistance to the US-23 strain but only moderate resistance to the aggressive NL13316 strain. Conversely, the Rpi-vnt1-positive MSKK1819 lines displayed complete resistance to NL13316 strain but only moderate resistance to US-23, highlighting the need for R-gene pyramiding.

A major bottleneck to introgression of the R-genes from S. pinnatisectum is the reproductive barrier between Solanum pinnatisectum and cultivated diploid potato. To address this, we have used bridge parents (MSJJ1821-01F2-049 and MSJJ1821-01F2-049-121) derived from Solanum verrucosum background, which facilitate successful crosses with S. pinnatisectum. Marker-assisted selection confirmed Rpi2 gene introgression in the progeny, providing a practical pathway for transferring this novel resistance gene into diploid potato germplasm. By pyramiding multiple R genes in our diploid potato germplasm, this research will contribute to addressing the challenge of durability against a rapidly evolving pathogen. Ultimately, this research advances potato breeding by developing diploid germplasm with broad-spectrum, durable resistance, a crucial step toward global food security and sustainable potato production.

Gashaw Belay Alemu (best poster)

Research: Unlike most crops, potatoes aren’t propagated from true seed, but rather clonally by planting tubers or tuber pieces, known as seed tubers. However, seed tubers can transmit numerous diseases that cause substantial yield loss for growers. In the cool highland tropics, the most destructive tuber-transmitted disease is bacterial wilt (also called brown rot), caused by the bacterium Ralstonia. 

Potato brown rot caused by African Ralstonia was long present in Madagascar, causing only minor yield losses. However, in the early 2000s potato growers in Madagascar experienced a devastating outbreak that severely reduced potato yields. Genetic testing revealed that a new outbreak was caused by a highly virulent pandemic Ralstonia strain that originated in the South American Andes, where it co-evolved with potato. 

I wanted to understand how the South American Ralstonia spread so fast and caused so much damage in Madagascar.  Was it a better pathogen than the African strain? I tested this hypothesis by inoculating growth chamber potato plants with the South American and the native African strain from Madagascar alone or together. 

My experiments showed the South American Ralstonia causes more disease at the cool temperatures typical of tropical highlands. Most importantly, the South American Ralstonia was more easily transmitted through infected seed tubers. While both strains caused latent (symptomless) infections, the South American strain was better at colonizing the potato tubers of asymptomatic plants. Despite reaching high population sizes in potato stems, the African Ralstonia strain very rarely colonized tubers, suggesting how the Andean pandemic lineage of Ralstonia strain displaced endemic Ralstonia strains in Madagascar.

We believe the South American strain spreads silently and efficiently through infected seed tubers, which are often exchanged from farmer to farmer in Africa. When the two strains were present together, the pandemic strain outcompeted the African endemic strain in potato tubers. This project highlights an important point that asymptomatic dissemination depends strongly on the type of Ralstonia strain involved in the epidemics. 

These findings explain the mystery of the Madagascar epidemic. More broadly, my results highlight the critical importance of robust seed certification systems, international pathogen monitoring, and strict quarantine measures to prevent the spread of highly aggressive and invasive pathogens like South American Ralstonia.