Page 226 - Plant Canada 2024 Proceeding

PLANT CANADA 2024

*[P44] FUNGICIDE TREATMENT EFFICACY FOR MITIGATING POWDERY SCAB AND PMTV IN
1
ALBERTA POTATO FIELDS: A FIELD STUDY EVALUATION. Muhammad Subhan Shafique , Michele
Konschuh , Jennifer Foster , Michael Harding , and Dmytro Yevtushenko . Department of Biological
1 1
3
1
2
Sciences, University of Lethbridge, Lethbridge, AB, Canada; Alberta Agriculture and Irrigation, Brooks,
2
AB, Canada; and Syngenta Canada Inc., Guelph, ON, Canada.
3
Correspondence to: dmytro.yevtushenko@uleth.ca

Powdery scab, a potato tuber disease caused by the plasmodiophorid pathogen Spongospora
subterranea f.sp. subterranea poses a significant threat to the potato industry. It causes tuber lesions and
root galls in potato plants. It is also the only known vector of potato mop-top virus (PMTV), which causes
internal necrosis (spraing) in stored potato tubers. The powdery scab lesions on the tuber surface affect
cosmetic appearance and reduce tuber quality for fresh market industries. It also poses challenges for
French fry and chip production in Alberta because deeper peeling may be required. The lesions can also
provide entry points for other pathogens, thereby affecting the long-term storage of potatoes. In the
summer of 2023, fields with a history of powdery scab were sampled and tested for the presence of S.
subterranea and PMTV using both morphological and molecular analyses. Trials were established in four
fields with confirmed presence of S. subterranea using a paired-plot design with three different potato
cultivars (Shepody, Russet Burbank, or Lady Claire) to evaluate the efficacy of five chemical treatments
provided by Syngenta: A21008A, Allegro-low, Allegro-medium, Allegro-high, and A24367B. The
fungicides were applied in-furrow at planting. Potato roots were evaluated for the presence and severity
of galls during the growing season. Tuber samples were collected at harvest to determine yield and
disease severity on tubers. Among the products tested, Allegro-medium demonstrated the best
suppression of root galls, followed by A24367B, whereas A21008A had the least effect. All treatments
showed significant scab suppression with Lady Claire, which was one of the most susceptible cultivars to
powdery scab among those tested in this study. No significant differences in marketable yield were
observed among treatments in any of the cultivars. The present findings have important implications for
developing management approaches to mitigate potato powdery scab under regional environmental
conditions.

[P46] AN EVOLUTIONARY LINEAGE OF FUSRIUM OXYSPORUM F.SP CUBENSETR4 CAUSING
NEW PANAMA DISEASE. Kyoko Watanabe , Shunsuke Nozawa , and Yousuke Seto . Graduate School
2 1
1
1
of Agriculture, Tamagawa University, Machida, Tokyo 194-8610, Japan; and Cancer Chemotherapy
2
Center, Japanese Foundation for Cancer Research, 3-8-31, Ariake, Koto-ku, Tokyo 135-8550, Japan
Correspondence to: wkyoko@agr.tamagawa.ac.jp

Fusarium oxysporum f. sp. cubense Tropical Race 4 (TR4) is the causal agent of New Panama Disease,
which causes serious problems in banana production. The fungus is a single race of Fusarium oxysporum
f. sp. cubense (FOC), sometimes referred to synonymously as F. odoratissimum. To understand the full
extent of damage caused by this race and to develop disease control measures, we analyzed NGS data
from 92 strains deposited in the genebank to determine what TR4 is.

Four thousand six hundred and three orthologous genes were analyzed, and the results showed that
FOC is polyphyletic, but TR4 diverged earlier than other formae speciales with FOC STR4 and f. sp.
cucumerinum clades, and the closest sister clade was STR4.Bayesian evolutionary analysis using a
sampling tree based on 100 predicted gene sequences indicated that TR4 separated into four gropes.
Most of the pathogens reported in different countries in recent years are grouped in one clade, originating
from Malaysia. However, there are also strains in Colombia, India and China that are somewhat different,
suggesting that they were not spread by a single invasion.

One of the characteristics of TR4 was that it encoded only the SIX8a gene, among the SIX8a and SIX8b
homologs of the FOC. It was also thought that only TR4 encodes the SIX8a gene, which is thought to be
involved in pathogenicity. On the other hand, the SIX8a gene was also reported to be present in F. sp.
sesami. In our study, it was re-confirmed that TR4 encodes a copy of the SIX8a gene and that the SIX8a
gene is also present in f. sp. sesami. Thus, the results support that the SIX8a gene is not unique to TR4.
Furthermore, we found that there are TR4 strains encoding not only the SIX8a gene but also the SIX8b
gene. We also reconfirmed the presence of multiple copies of the SIX8b gene in FOC race1, f. sp.
lycopersici. The phylogenetic tree based on this gene did not match the genome-scale phylogenetic tree

225