Resistance response of fifteen sweet potato genotypes to scab disease (Sphaceloma batatas) in two growing sites in East Nusa Tenggara, Indonesia

Mau YS. 2018. Resistance response of fifteen sweet potato genotypes to scab disease (Sphaceloma batatas) in two growing sites in East Nusa Tenggara, Indonesia. Trop Drylands 2: 5-11. Field experiments were carried out in two growing locations involving potential sweet potato clones from East Nusa Tenggara Province, Indonesia to: (i) evaluate scab resistance levels of the sweet potato clones, and (ii) identify sweet potato clones with good resistance level to scab disease. The experiment was carried out in the fields employing a Randomized Block Design with a mono-factorial treatment design in each location. The treatment assigned was sweet potato genotype, each consisted of two replicates. The variables observed were disease severity that was assessed at 2, 4, 6, and 8 weeks after inoculation (WAI), which then was used to calculate the Area Under the Disease Progress Curve (AUDPC) of the disease severity. The ANOVA of AUDPC was used to determine the treatment effect, and the disease severity at 8 WAI was used to assess scab resistance level of the sweet potato genotypes tested. The study results showed highly significant differences of disease severities among the tested sweet potato genotypes within each trial location. The majority of the genotypes tested were classified "resistant" or "moderately resistant" to scab disease, except the check clone SLM-01 and KRA-01 that were, respectively, "susceptible" and "moderately susceptible" to scab disease. The majority of sweet potato genotypes evaluated were consistent in their resistance performance in the two trial locations.