Volume 63, Number 1, April 2026

Sugarbeets are largely produced without irrigation, making
drought stress inevitable when rainfall is insufficient.
Whether drought stress impacts root storage, however, is
currently unknown. Research was conducted to determine
the effect of preharvest water stress on postharvest sugarbeet
root respiration rate and susceptibility to storage rots
as these traits are the primary determinants for sucrose loss
and quality deterioration. Greenhouse-grown plants were
subjected to four levels of water deficit by discontinuing
watering for 0, 7, 14 or 21 days prior to harvest. Plants receiving
water-restrictive treatments displayed physiological
stress by leaf epinasty, reductions in net photosynthetic
rate and leaf relative water content and increases in leaf
temperature, whereas the water content of roots harvested
from these plants progressively decreased with the severity
of the preharvest water-deficit treatment. Harvested roots
from all watering treatments were stored at 10°C and 95%
relative humidity for up to 12 weeks and evaluated for respiration
rate and susceptibility to storage rot. Root respiration
rate during storage was inversely related to root water
content at harvest by second-order equations, such that respiration
was not significantly affected by minor reductions
in root water content but increased exponentially for roots
obtained from severely drought-stressed plants with water
contents at harvest of ≤75%. Similarly, roots with water
contents ≤75% had elevated levels of electrolyte leakage,
a measure of cellular membrane damage, and were more
susceptible to dehydration and fungal infection during
storage. In separate experiments, roots harvested from water-
stressed plants were inoculated with Botrytis cinerea or
Penicillium vulpinum, two causal agents for storage rots.
In these experiments, preharvest water stress quantitatively
increased root rot and qualitatively altered symptoms
of their infection. Overall, these results demonstrate that
severe preharvest drought stress is likely to significantly
increase sugarbeet root storage losses caused by root respiration
and storage rots and that storage losses are likely
to accelerate with time in storage. However, mild-to-moderate
drought conditions prior to harvest are expected to
have no or minimal effect on storage losses from root respiration
or storage rots.

In Michigan, sugarbeets (Beta vulgaris) are stored for up
to 200 days postharvest, during which time sugar loss may
occur as a result of energy use from respiration and factors
such as rot. Cercospora leaf spot (CLS) has been considered
a potential predisposing factor for increased storage
rot. To investigate these impacts, field and postharvest
studies evaluated storage rot symptom development in
sugarbeets with designated “high” or “low” in-season
CLS severity. Root slices of sugarbeets from each CLS
level were inoculated with Fusarium graminearum,
Botrytis cinerea, or Penicillium vulpinum, and symptoms
were assessed after 7 days. Across three CLS-susceptible
commercial varieties, there were no significant differences
among storage rot susceptibility to any of the tested
pathogens in hand-harvested sugarbeets, regardless of
CLS level, at any storage time point in 2020 or 2021 (P >
0.05). In studies using CLS-susceptible and -resistant germplasm
and varieties, CLS effects were inconsistent and
only significant in one parameter at two out of six storage
time points across these years (P < 0.05). Across storage
pathogens, prior CLS level also did not impact root respiration
or the change in respiration rate from initial to final
storage time point in either 2021 or 2023 (P
> 0.05). Of note, B. cinerea caused more severe symptoms
than other pathogens in these studies (P < 0.05). Finally,
varietal responses differed significantly to storage pathogens
(P < 0.05) and may be of interest to future cultivar
development efforts. This research increases our understanding
of factors contributing to potential storage losses,
which will improve yield and profit for sugar growers

Endogenous metabolism is primarily responsible for
losses in sucrose content and processing quality in postharvest
sugarbeet roots. The genes responsible for this
metabolism and the transcriptional changes that regulate
it, however, are largely unknown. To identify genes and
metabolic pathways that participate in postharvest sugarbeet
root metabolism and the transcriptional changes that
contribute to their regulation, transcriptomic and metabolomic
profiles were generated for sugarbeet roots at harvest
and after 12, 40 and 120 d storage at 5 and 12°C and
gene expression and metabolite concentration changes
related to storage duration or temperature were identified.
During storage, 8656 genes, or 34% of all expressed
genes, and 225 metabolites, equivalent to 59% of detected
metabolites, were altered in expression or concentration,
indicating extensive transcriptional and metabolic
changes in stored roots. These genes and metabolites contributed
to a wide range of cellular and molecular functions,
with carbohydrate metabolism being the function
to which the greatest number of genes and metabolites
classified. Because respiration has a central role in postharvest
metabolism and is largely responsible for sucrose
loss in sugarbeet roots, genes and metabolites involved in
and correlated to respiration were identified. Seventy-five
genes participating in respiration were differentially expressed
during storage, including two bidirectional sugar
transporter SWEET17 genes that highly correlated with
respiration rate. Weighted gene co-expression network
analysis identified 1896 additional genes that positively
correlated with respiration rate and predicted a pyruvate
kinase gene to be a central regulator or biomarker for respiration
rate. Overall, these results reveal the extensive
and diverse physiological and metabolic changes that
occur in stored sugarbeet roots and identify genes with
potential roles

Cercospora leaf spot (CLS; causal agent Cercospora beticola
Sacc.) is endemic in many sugar beet production
regions due to the widespread distribution of C. beticola
and the inability of current management practices to provide
complete control of the disease. Roots harvested from
plants with CLS, therefore, are inevitably incorporated into
sugar beet root storage piles, even though the effects of
CLS on root storage properties are largely unknown. Research
was conducted to determine the effects of CLS on
storage properties including root respiration rate, sucrose
loss, invert sugar accumulation, loss in recoverable sucrose
yield, and changes in sucrose loss to molasses with respect
to CLS disease severity and storage duration. Roots were
obtained from plants with four levels of CLS severity in
each of three production years, stored at 5°C and 95% relative
humidity for up to 120 days, and evaluated for storage
characteristics after 30, 90, and 120 days storage. No
significant or repeatable effects of CLS on root respiration
rate, sucrose loss, invert sugar accumulation, loss in recoverable
sucrose yield, or change in sucrose loss to molasses
were detected after 30, 90, or 120 days storage regardless
of the severity of CLS disease symptoms. Therefore, no
evidence was found that CLS accelerates sugar beet storage
losses, and it is concluded that roots harvested from
plants with CLS can be stored without additional or specialized
precaution, regardless of CLS symptom severity.

The nematophagous fungus Hyalorbilia oviparasitica and
relatives (Hyalorbilia spp.) are known to parasitize several
endoparasitic nematodes. In this project, we hypothesized
that indigenous populations of this fungus could
be used to predict nematode suppression in agricultural
field soils. We quantified Hyalorbilia spp. in soil samples
from 44 different sugarbeet fields in the Imperial Valley
of California. Seven soils harboring Hyalorbilia spp. and
two that tested negative for the fungi were examined for
nematode suppressive activity. Untreated and autoclaved
portions of each soil were planted with cabbage and infested
with sugar beet cyst nematode (Heterodera schachtii)
juveniles. Females and cysts of H. schachtii were enumerated
after 12 weeks. In the seven soils harboring Hyalorbilia
spp., females and cysts in the untreated soils were
reduced by 61 to 82% compared with the autoclaved controls.
Soils with no detectable Hyalorbilia spp. exhibited
no nematode suppression. Two novel Hyalorbilia strains,
HsImV25 and HsImV27, were isolated from H. schachtii
females reared in field soil using an enrichment and double-
baiting cultivation technique. Both strains suppressed
H. schachtii populations by more than 80% in soil-based
assays, confirming that Hyalorbilia spp. are the likely
causal agents of the nematode suppression in these soils.
This study demonstrated that indigenous populations of a
hyperparasite (Hyalorbilia spp.) in agricultural field soils
predicted suppressive activity against a soilborne plant
pathogen (H. schachtii). To our knowledge, this is the first
report to demonstrate this capability. We anticipate that this
research will provide a blueprint for other similar studies,
thereby advancing the field of soilborne biological control.

The sugar beet root maggot (SBRM), Tetanops myopaeformis
(von Röder), is a devastating insect pathogen of
sugar beet (SB), Beta vulgaris, ssp vulgaris (B. vulgaris),
an important food crop, while also being one of only two
plants globally from which sugar is widely produced, and
accounting for 35% of global raw sugar with an annual
farm value of $3 billion in the United States alone. SBRM
is the most devastating pathogen of sugar beet in North
America. The limited natural resistance of B. vulgaris necessitates
an understanding of the SBRM genome to facilitate
generating knowledge of its basic biology, including
the interaction between the pathogen and its host(s). Presented
is the de novo assembled draft genome sequence of
T. myopaeformis isolated from field-grown B. vulgaris in
North Dakota, USA. The SBRM genome sequence TmSBRM_
v1.0 will also be valuable for molecular genetic
marker development to facilitate host resistance gene identification
and knowledge, including SB polygalacturonase
inhibiting protein (PGIP), and development of new control
strategies for this pathogen, relationship to model genetic
organisms like Drosophila melanogaster and aid in agronomic
improvement of sugar beet for stakeholders while
also providing information on the relationship between the
SBRM and climate change.

Tetanops myopaeformis, the sugar beet root maggot
(SBRM), is a devastating insect pathogen of sugar beet,
one of only two plants in the world from which sugar is
widely produced, accounting for 55% of U.S. sugar and
35% of global raw sugar with an annual farm value of $3
billion in the United States. T. myopaeformis is capable of
causing total crop failure, making its study important. The
previously released SBRM genome, TmSBRM_v1.0, has
been generated from the de novo assembled draft genome
sequence of T. myopaeformis isolated that was isolated
from field-grown B. vulgaris in North Dakota, USA. The
annotation of the T. myopaeformis is presented here. The
annotated T. myopaeformis genome should be useful in understanding
the biology of this insect and the development
of new control strategies for this pathogen, relationship to
model genetic organisms like Drosophila melanogaster
and aid in agronomic improvement of sugar beet for stakeholders
while also providing information on the relationship
between the SBRM and climate change.

Pathogen-secreted polygalacturonases (PGs) alter plant
cell wall structure by cleaving the α-(1 → 4) linkages
between D-galacturonic acid residues in homogalacturonan
(HG), macerating the cell wall, facilitating infection.
Plant PG inhibiting proteins (PGIPs) disengage pathogen
PGs, impairing infection. The soybean cyst nematode,
Heterodera glycines, obligate root parasite produces secretions,
generating a multinucleate nurse cell called a
syncytium, a byproduct of the merged cytoplasm of 200–
250 root cells, occurring through cell wall maceration.
The common cytoplasmic pool, surrounded by an intact
plasma membrane, provides a source from which H. glycines
derives nourishment but without killing the parasitized
cell during a susceptible reaction. The syncytium
is also the site of a naturally-occurring defense response
that happens in specific G. max genotypes. Transcriptomic
analyses of RNA isolated from the syncytium undergoing
the process of defense have identified that one
of the 11 G. max PGIPs, GmPGIP11, is expressed during
defense. Functional transgenic analyses show roots undergoing
GmPGIP11 overexpression (OE) experience
an increase in its relative transcript abundance (RTA) as
compared to the ribosomal protein 21 (GmRPS21) control,
leading to a decrease in H. glycines parasitism as
compared to the overexpression control. The GmPGIP11
undergoing RNAi experiences a decrease in its RTA as
compared to the GmRPS21 control with transgenic roots
experiencing an increase in H. glycines parasitism as
compared to the RNAi control. Pathogen associated
molecular pattern (PAMP) triggered immunity (PTI)
and effector triggered immunity (ETI) components are
shown to influence GmPGIP11 expression while numerous
agricultural crops are shown to have homologs.