Susceptibility of Ethiopian Released Potato Varieties to Potato Tuber moth, Phthorimae operculella Infestation under the field and laboratory conditions

Two experiments were designed for studying susceptibility of ten potato varieties to evaluate the infestation levels of Phthorimaea operculella under the field and laboratory conditions, at the egg stage and larval infestation stage before harvesting, at harvesting time, and evaluates the physiological performance to resist PTM. Data were analyzed using Mean ± Standard Error, along with F-values and P-values to assess statistical significance with R software. There was significant differences in egg infestation levels and suggesting a clear variation in susceptibility between genotypes to PTM (F-value = 3.1, P-value = 0.018), highest infestations observed on the Belete (14.4 ± 7.9) and Burika (7.5 ± 6.7) varieties, and the lowest on Menagesha (1.26 ± 0.26), Badhasa (2.4 ± 4), and Jalenie (2.86 ± 3). The infestation levels of different genotypes at various larval instars stages (1st, 2nd, 3rd, and 4th ) across three count periods, 1st instars stage, infestation levels remained low across all genotypes, Belete showing no infestation, while Gudene exhibited the highest mean infestation (0.46 ± 0.80). No significant differences among genotypes (P > 0.05). In the 2nd instars stage, infestation increased in count 2, particularly in Wechecha (1.95 ± 1.17) and Bubu (1.90 ± 0.45), but decreased in count 3, a significant variation in infestation was found (P = 0.010). The 2nd instars stage, in particular, is crucial for survival since larvae typically experience the highest mortality rates during early developmental stage. A high infestation in the 2nd instars, as seen in Zemen, may indicate that larvae find the plant more suitable for development at that stage. The 3rd instars stage exhibited infestation trends similar to the 2nd instars, with Gudene (1.51 ± 0.61) and Bubu (1.25 ± 0.58) havi1*ng higher values. However, no statistically significant differences were observed (P > 0.05) and 4th the instars stage showed generally low infestation levels. Zemen (0.85 ± 0.47) having the highest infestation. Overall, while infestation varied across developmental stages and genotypes, significant differences were only detected at the 2nd instars stage. Zemen being the most affected genotype, Gudene and Burika showing the least infestation across all stages. There was significance difference among the genotypes on leaf damage (F = 3.49, P = 0.011), Badhasa and Zemen exhibited the highest leaf damage (28%), while Belete, Jalenie, and Gudene had the lowest (0.66%). In contrast, petiole damage showed no significant variation among genotypes (F = 0.42, P = 0.9). Significant differences (p < 0.05) were observed for plant height, stand count per plot, and canopy coverage. Plant height ranged from 36.9 ± 3.3 cm (Zemen) to 54.8 ± 2.7 cm (Wechecha). Canopy coverage varied significantly, with Zemen exhibiting the lowest value (0.59 ± 0.12), while Bubu, Burika, and Jalenie had the highest (0.86–0.87) , Jalenie and Burika also showed relatively high dry matter content (0.87 ± 0.01 and 0.86 ± 0.04, respectively), suggesting that these traits are strongly influenced by genotype selection. Under laboratory test Belete had the lowest penetrating levels in both choice (1.32 ± 3.1%) and non-choice (10.6 ± 3.8%). the presence of inherent endophylactic resistance traits. Such genotypes likely, may possess structural or biochemical deterrents (e.g., thick periderm, high glycoalkaloid levels, or low volatile emissions), which make them unattractive or unpalatable to the larvae. The findings provide insights for selecting high-yielding and high-quality potato varieties for improved agricultural productivity.