Assessing zebra chip resistance of advanced potato clones under field conditions in the Toluca valley, Mexico

Zebra chip, also known as ‘potato purple-top’ and ‘internal tuber browning’ is threatening potato production in Mexico, Central America, the United States, and New Zealand. The disease is caused by the phloem-limited ‘Candidatus Liberibacter solanacearum’ (Lso), for which potato psyllid, Bactericera cockerelli is the vector. Currently, ZC management is mainly based on insecticide applications targeted against the potato psyllid, underscoring the need for development of potato varieties that are resistant to Lso and/or potato psyllid. A field study was carried out during three years in the Toluca Valley, Mexico, to assess the zebra chip resistance of six advanced potato clones. In addition, the commercial variety Fianna was included as a control. There were no significant differences in yield and number of potato psyllid nymphs per plant among the seven potato clones. However, significant differences were observed in the percentage of healthy tubers, area under disease progress curve in the foliage and in the severity of the internal tuber discoloration. The six potato clones showed higher tolerance to ZC symptoms than Fianna.