Over the past few years, the potato production of the U.S., Mexico, New Zealand and Central America has been under threat by zebra chip, a disease associated with the Candidatus Liberibacter solanacearum (Lso) bacteria, vectored by the tiny potato psyllid insect (Bactericera cockerelli). The disease turns part of the amide in soluble sugars so that when potatoes are cooked, sugars caramelize and streaks appear.
Zebra chip is currently combated with pesticides, but sustainable defense requires the development of resistant and/or tolerant varieties.
Entomologists from the University of California, Riverside, together with researchers from INIFAP (Mexico), characterized four promising potato lines (246, 865, 510, NAU) exposed to Lso-positive adult psyllids and monitored the vectors’ behavior toward the plants and the effects of the bacteria on the tubers. The potato lines were compared to zebra chip-susceptible variety Atlantic.
Results showed that the psyllid preferred to settle on Atlantic, 246 and 865 and oviposit on Atlantic compared to 510. However, tolerance to zebra chip appeared more dependent on the host’s responses to Lso infection. All four genotypes exhibited putative zebra chip tolerance in raw tubers compared to the susceptible Atlantic. Expressed tolerance was associated with reduced concentrations of phenolic compounds in Lso-infected raw tubers compared to Altlantic tubers. Lower phenol concentrations corresponded to a reduction of symptoms in freshly cut tubers. However, the four genotypes showed zebra chip-related coloring in fried potatoes due to an increase of the sugar content, typical of Lso infection. This means that, despite their being tolerant to zebra chip, they are not suitable for the chip industry.
“Considering that in Mexico, the production of potatoes for the fresh market is almost 60 percent against the 30 percent of industry potatoes, these four lines might be useful for the former,” researchers wrote, “without forgetting that they might be used in genetic improvement programs to develop new, more tolerant and/or resistant varieties.”
Source: Fresh Plaza