Greens Continued from Page 11
teria, and thesenutrientsdifferdepending on the lettuce genotype,” she said. “The plant genotype has a large effect on the metabolites released to the bacteria.” She said these chemical differences on lettuce leavesmay also include significant differences in levels of substances that re- duce pathogen populations. “GreenTowers isourmost resistant vari- ety, andtheremaybemoreanti-microbials in resistant varieties,”Melotto said. This detailed study of the environment on lettuce leaves when the crop is still
As part of one multi-year study, re- searchers are comparing lettuce variet- ies grown in Salinas, Davis and Imperial County in terms of the length of time after harvest before the first signs of damage appear; cell wall strength and elasticity; size and physiology of the leaves; and the nutritional quality of the crop. Studies have already shown that the place to look intesting fordifferences inthe postharvest life of lettuce varieties is in the
newer leaves near the center of the plant. “In lettuce cultivars that deteriorate quickly, it is the inner leaves that dete- riorate quickly,” said Ivan Simko, a U.S. Department of Agriculture research ge- neticist based in Salinas. “In cultivars that deteriorate slowly, the inner leaves deteri- oratemore slowly.” ( Bo b J o hn s o n i s a r e p o r t e r i n Sacramento. He may be contacted at bjohn11135@gmail.com.)
Studies are showing, for example, that a smaller number and size of stomata can reduce the development of pathogens on the leaves, as can larger-sized cells. Researchers are exploring the possibil- ity that breeding for varieties appealing to consumersmayhave resulted incommer- cial lettuce varieties that aremore suscep- tible to contaminationbyE. coli andother food safety threats thanwild types. Waxy leaves alsomake for lower patho- gen populations in lettuce, researchers
Red cabbage provides source of new cyan blue food coloring
“There isn’t a magical gene for shelf life, but we have located five key genetic areas.” —Gail Taylor UC Davis
and Italy has beenworking for about a de- cade toisolateablueanthocyaninfromred cabbage—but the natural blue coloring is present only in tiny amounts. UCDavis researchers figured out a way to convert other anthocyanins in cabbage into the cyan blue color compound. Professor Justin Siegel and graduate student Pamela Denish have founded a startup company, Peak B, to develop the technology for commercial applications. Havingtherightbluecolor isalsoimport- ant formixingothercolors, suchasgreen. If the blue isn’t right, it will producemuddy, browncolorswhenmixed, Siegel said.
A newblue food coloring, derived from redcabbage, showspromiseas analterna- tive to synthetic blue food colorings. An international team of researchers that includedchemists fromtheUniversity of California, Davis, reported the findings earlier thismonth. Redcabbageextractsarewidelyusedasa source of natural food colorings—particu- larly redsandpurples—froma typeof dyes knownas anthocyanins, UCDavis said. A team led by scientists fromMars Inc. and including the UC Davis research- ers and colleagues from the Ohio State Universityandinstitutions inJapan,France
growing is also related to the search for varieties that will last longer after harvest. “We are also working on long-shelf-life leaves,” Taylor said. “There isn’t amagical gene for shelf life, but we have located five key genetic areas.” Some lettuce varieties last nearly twice as longasothersafterharvest. Researchers said theyareattempting tounderstand the details of why this is, so they can improve shelf life of future lettuce varieties.
said, although theymay not be as appeal- ing to consumers. Higher levels of ethylene or jasmonic acid are associated with lower pathogen levels, as lower levels of nitrogen, phos- phorous and potassium are available to themicrobes. Melottosaid lettuceplants alsohavedif- ferent chemistries that affect howmuch food thepathogens can findon the leaves. “Therearenutrientsavailable tothebac-
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12 Ag Alert April 21, 2021
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