Physiological Responses of the Potato Tuberworm (Phthorimaea operculella) to Potato (Solanum tuberosum) Germplasm

The potato tuberworm, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), is an important field and storage pest of potato Solanum tuberosum L. Feeding indices and midgut digestive protease and amylase enzyme activities were measured under laboratory conditions in P. operculella larvae reared on leaves of eight potato genotypes including Agria, Ausonia, Khavaran, Kondor, Morene, Satina, Savalan, Sprint, and two Iranian potato selections PI396124 and PI397082–2. The highest amounts efficiency of conversion of ingested food, and efficiency of conversion of digested food, were recorded in larvae reared on Savalan, and the lowest amount of these indices found on Khavaran, Agria, and PI397082–2. There were significant positive correlations between coefficients of P. operculella with midgut protease enzyme activity, and no significant correlations between the indices and midgut amylase enzyme activity. Among tested potato genotypes, the highest proteolytic activity was found on Savalan (6.6 ± 0.07 U/mg), and the lowest activity observed on Khavaran (4.4 ± 0.09 Umg −1) and Agria (4.4 ± 0.14 Umg −1).