Outlook of Cassava Brown Streak Disease Assessment: Perspectives of the Screening Methods of Breeders and Pathologists
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Date
2021
Journal Title
Journal ISSN
Volume Title
Publisher
Frontiers in plant science
Abstract
Cassava production and productivity in Eastern, Central, and Southern Africa are ravaged
by cassava brown streak disease (CBSD), causing yield losses of up to 100% when
susceptible varieties are grown. Efforts to develop CBSD-resistant clones are underway.
However, the methods for screening CBSD resistance currently vary between breeders
and pathologists, with the limited empirical data to support their choices. In this study,
we used the empirical CBSD foliar and root necrosis data from two breeding populations,
termed cycle zero (C0) and cycle one (C1), to assess and compare the effectiveness of the
CBSD screeningmethods of breeders vs. pathologists. On the one hand, the estimates of
broad-sense heritability (H2) for the CBSD root necrosis assessment of breeder ranged
from 0.15 to 0.87, while for the assessment method of pathologists, H2 varied from
0.00 to 0.71 in C0 clones. On the other hand, the marker-based heritability estimates
(h2) for C0 ranged from 0.00 to 0.70 for the assessment method of breeders and from
0.00 to 0.63 for the assessment method of pathologists. For cycle one (C1) population,
where both foliar and root necrosis data were analyzed for clones assessed at clonal
evaluation trials (CETs) and advanced yield trials (AYTs), H2 varied from 0.10 to 0.59
for the assessment method of breeders, while the H2 values ranged from 0.09 to 0.35
for the CBSD computation method of pathologists. In general, higher correlations were
recorded for foliar severity from the assessment method of breeders (r = 0.4, p ≤ 0.01 for
CBSD3s and r = 0.37, p ≤ 0.01 for CBSD6s) in C1 clones evaluated at both clonal and
advanced breeding stages than from the approach of pathologists. Ranking of top 10 C1
clones by their indexed best linear unbiased predictors (BLUPs) for CBSD foliar and root
necrosis showed four overlapping clones between clonal and advanced selection stages
for themethod of breeders;meanwhile, only a clone featured in both clonal and advanced
selection stages from the CBSD assessment method of pathologists. Overall, the CBSD
assessment method of breeders was more effective than the assessment method of
pathologists, and thus, it justifies its continued use in CBSD resistance breeding.
Description
Keywords
Cassava, Resistance, Breeder’s, pathologist’s, Cassava brown streak disease
Citation
Ozimati, A. A., Esuma, W., Alicai, T., Jannink, J. L., Egesi, C., & Kawuki, R. (2021). Outlook of Cassava Brown Streak Disease Assessment: Perspectives of the Screening Methods of Breeders and Pathologists. Frontiers in plant science, 12. doi: 10.3389/fpls.2021.648436