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

Abstract

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.

Characterization of the Tolerance against Zebra Chip Disease in Tubers of Advanced Potato Lines from Mexico

“…In all the bioassays conducted (choice and no-choice), the raw tubers of the four experimental lines showed lower ZC intensity scores than the Atlantic variety, although the presence of Cls in tubers was confirmed by qPCR analyses. These tests, performed under controlled conditions, confirm what was observed under field conditions in the Toluca Valley, Mexico, although the variety Fianna was used as a control (Rubio-Covarrubias et al 2013;Rubio-Covarrubias et al 2015). Interestingly, the tubers from the choice test showed lower discoloration index than those from the no-choice.…”

“…This situation favors the selection of potato genotypes that do not show ZC symptoms or present, to a lesser extent, internal discoloration in raw tubers. NAU and 510 have already been commercially planted by potato growers in Mexico and have been widely accepted because, besides their low susceptibility to internal discoloration of the tubers, they have also shown good agronomic and commercial characteristics (Rubio-Covarrubias et al 2013;Rubio-Covarrubias et al 2015).…”

“…A commercial potato variety, Atlantic, was included as a control. In previous field evaluations in Mexico, the four advanced clones have shown tolerance against ZC (Cadena-Hinojosa et al 2003;Rubio-Covarrubias et al 2013;Rubio-Covarrubias et al 2015). In addition, in the same field tests carried out in the Toluca Valley, which is regarded as the origin center of Phytophthora infestans (Alarcón-Rodríguez et al 2014), the clones 865 and 246 have exhibited tolerance to late blight.…”

“…The use of resistant (or tolerant) varieties is a basic component of integrated pest control and represents a long-term sustainable management strategy for ZC. A number of breeding programs for ZC resistance are underway in ZC-affected countries and are focused on the generation of resistant genotypes (Cadena-Hinojosa et al 2003;Butler et al 2011a;Anderson et al 2012;Diaz-Montano et al 2014;Rubio-Covarrubias et al 2015;Cooper and Bamberg 2014;Novy et al 2013;Munyaneza et al 2013;Scheuring et al 2013;Wallis et al 2015a). While a few potato lines have been found to be tolerant to ZC, no tolerant or resistant varieties have yet been released.…”

“…In Mexico, researchers of INIFAP (Instituto Nacional de Investigaciones Forestales Agrícolas y Pecuarias en México [National Institute for Forestry, Agriculture and Livestock Research in Mexico]) generated potato genotypes that exhibited resistance against ZC (Cadena-Hinojosa et al 2003;Rubio-Covarrubias et al 2013;Rubio-Covarrubias et al 2015). These have been screened under field conditions and results indicate that some advanced lines have lower ZC incidence and less intense internal tuber discoloration.…”