Abstract
Six named potato cultivars were compared for degree of tuber infestation by potato tuber moth, Phthorimaea operculella Ziller in two seasons trials. A statistical study of correlation and multivariate analysis on the susceptibility of six cultivars of potato harvested in Egypt was carried out to establish the relationships between the physic-chemical compounds of crust and varieties susceptibility to potato tuber moth. The main characters studied were tuber crust colours; number and depth of eyes and some agricultural practices were evaluated. Differences occurred between cultivars in the mechanical resistance of the crust of tubers to puncture and in the number of eyes per tuber. When cultivars were ranked according to percentage of infestations, there was close correlation with ranking based on the degree of infestation in the field. Agriculture at a depth of 30 cm delay and reduce the proportion of tubers infestation, (Cara after 51.0 and 49.0 days, Hermis 47.0 and 51.0 days, Sponta 44.0 and 49.0 days, Nicola 43.0 and 49.0 days, Lady Rosetta 41.0 and 39.0 days and finally Diamonda 41.0and 49.0 days, season 2016 and season 2017, respectively). These important results in the study can be summarized according to sensitivity and the beginning of tuber infestation ascending: Lady Rosetta (43.75 days); Nicola (51.95 days); Hermis (56.4 days); Diamonda (63.75 days) and Sponta and Cara (65.75 days) season, 2017. Otherwise, the sensitivity of different varieties is as follow season, 2016 Lady-Rosetta (42.0 days); Hermis (51.0 days); Nicola (55.5days); Diamonda (61.0 days); Cara (63.5 days) and Sponta (66.5days). It was revealed that, the less preference varieties for adults are Sponta, Cara and Diamond, (66.5 and 65.75 days; 63.5 and 65.75 days and 61.0 and 63.75 days, season 2016 and season 2017, respectively. The tuber crust colour, the number and depth eyes, the early types of maturing and the dryness of the soil are important factors in determining the rate of infections among the tested varieties.