Submitted to: Journal of Crop Science and Biotechnology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/15/2014
Publication Date: 6/16/2014
Citation: Nyankanga, R.O., Kiplagat, K.W., Narla, R.D., Shibairo, S.I., Kabira, J.N., Landeo, J.A., Olanya, O.M. 2014. Effects of early and late harvest on agronomic performance and stability of late blight resistant (R-gene free) potato genotypes. Journal of Crop Science and Biotechnology. 17:89-96. Interpretive Summary: Late blight is a significant constraint to potato production in diverse regions. Knowledge of agronomic performance of late blight resistant genotypes can be utilized to improve potato production. We evaluated two potato harvest dates, consisting of early (90 days) and late (120 days) in a tropical highland environment during 2005 and 2006. Late blight development, tuber yield, and yield stability were assessed in this study. Although differences in late blight levels were recorded among genotypes and between locations, resistant potato genotypes with quantitative resistance had better tuber yield at late than early harvest. Disease development was greater during in 2006 than 2005 years. The use of multi variate quantitative technique such as additive main effects and multiplicative interaction model can enhance assessment of yield stability and deployment of late blight resistant cultivars in suitable environments.
Technical Abstract: To assess the effectiveness of genotype resistance to potato late blight, foliar blight development, area under disease progress curves (AUDPC) and tuber blight were quantified. Late blight resistant potato genotypes (R-gene free) were assessed for yield performance and stability at early (90 days) and late (120 days) harvest dates at two locations in Kenya during a two year period. Significant differences (P < 0.05) in AUDPC were detected among genotypes. Resistant genotypes free of R-genes performed better at late than early harvest, but tuber yield varied among genotypes and locations. The rankings of genotypes for disease severity, late blight resistance, and tuber yield varied across seasons and locations. Additive main effects and multiplicative interaction (AMMI) analysis of tuber yield and late blight resistance showed that the effects of genotypes (G), environments (E) and the G X E interactions were significant (P<0.05). The proportion of genotypic variance was larger than that the environmental variance and the G X E interaction. On tuber yield, the G, E and G X E interactions accounted for 43%, 53.4%, 39.6% of the variation at early harvest, and 29.7%, 17.5% and 16.9% during late harvest. For AUDPC, G, E, and G x E accounted for 80.2% 82.3%, and 5.0% and 4.6%, 14.8% and 13% for early and late harvest, respectively. The resistance of R-gene free potato genotypes varied and tuber yield was comparatively greater at late than early harvests.