Location: Plant, Soil and Nutrition ResearchTitle: Genetic variation and trait correlations in an East African cassava breeding population for genomic selection
|OZIMATI, ALFRED - National Crops Resources Research Institute|
|KAWUKI, ROBERT - National Crops Resources Research Institute|
|ESUMA, WILLIAMS - National Crops Resources Research Institute|
|KAYONDO, SIRAJ - National Crops Resources Research Institute|
|PARIYO, ANTHONY - National Crops Resources Research Institute|
|WOLFE, MARNIN - Cornell University - New York|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/27/2018
Publication Date: 1/24/2019
Citation: Ozimati, A., Kawuki, R., Esuma, W., Kayondo, S.I., Pariyo, A., Wolfe, M., Jannink, J. 2019. Genetic variation and trait correlations in an East African cassava breeding population for genomic selection. Crop Science. 59(2):460-473. https://doi.org/10.2135/cropsci2018.01.0060.
Interpretive Summary: The Ugandan national cassava breeding program has initiated the use of genome-wide DNA markers in their selection efforts. We analyzed progress made from this approach. We documented only small progress in yield, but better progress in disease resistance and dry matter content. We showed that some traits measured on seedlings correlates well with those measured at later stages, promising to accelerate breeding. Results from this study will guide improved breeding practices in Uganda and elsewhere in eastern Africa.
Technical Abstract: Cassava (Manihot esculenta Crantz) is a major source of dietary carbohydrates for >700 million people globally. However, its long breeding cycle has slowed the rate of genetic gain for target traits. This study aimed to assess genetic variation, the level of inbreeding, and trait correlations in genomic selection breeding cycles. We used phenotypic and genotypic data from the National Crops Resources Research Institute (NaCRRI) foundation population (Cycle 0, C0) and the progeny (Cycle 1, C1) derived from crosses of 100 selected C0 clones as progenitors, both to evaluate and optimize genomic selection. The highest broad-sense heritability (H2 = 0.95) and narrow-sense heritability (h2 = 0.81) were recorded for cassava mosaic disease severity and the lowest for root weight per plot (H2 = 0.06 and h2 = 0.00). We observed the highest genetic correlation (rg= 0.80) between cassava brown streak disease root incidence measured at seedling and clonal stages of evaluation, suggesting the usefulness of seedling data in predicting clonal performance for cassava brown streak root necrosis. Similarly, high genetic correlations were observed between cassava brown streak disease severity (rg= 0.83) scored at 3 and 6 mo after planting (MAP) and cassava mosaic disease, scored at 3 and 6 MAP (rg= 0.95), indicating that data obtained on these two diseases at 6 MAP would suffice. Population differentiation between C0 and C1 was not well defined, implying that the 100 selected progenitors of C1 captured the diversity in the C0. Overall, genetic gain for most traits were observed from C0 to C1.