Aphid-resistant varieties of lettuce now provide a viable alternative for growers hit by the devastating pest over the past few years.
Dutch company Rikj Swaan had bred resistance into most commercial lettuce varieties, using conventional breeding techniques rather than genetic modification, says John Phillips, seed manager of Auckland company Terranova Seeds.
The
company supplies commercial and home-garden growers nationwide.
Mr Phillips said work on developing the resistant strain had been going on for 20 years but only lately had the lettuces become commercially viable, particularly for the New Zealand market.
The resistant characteristic was first identified in a wild lettuce strain, and had been bred into established varieties, which were initially too small to be economical, he said.
The breeding breakthrough came when the gene conferring aphid resistance was isolated from the gene regulating plant size, producing a good-sized resistant lettuce.
"The first varieties released overseas weren't as large as the New Zealand market prefers, with the big size and lots of outer leaves."
But subsequent breeding had established bigger lettuces that appealed to New Zealand consumers.
Mr Phillips said the resistance was strong and stable. Two lettuces growing side by side, one resistant and the other not, would produce totally different results, with the susceptible variety being infested with aphids but the resistant variety unaffected.
The price difference of the resistant strains was reasonably significant, but they needed less spraying.
"Yes, there is a tradeoff but it also offers peace of mind."
He said lettuce aphid infestations peaked over summer and autumn, which made use of the resistant varieties particularly worthwhile in those seasons.
- NZPA
