SuperSour

More SuperSour Rootstocks Under Study

Daniel CooperRootstocks

“Superior New Rootstocks Can Make Citrus Profitable Again” is the headline of a recent U.S. Department of Agriculture Agricultural Research Service (USDA ARS) article. Kim Bowman, research geneticist at the USDA Horticultural Research Laboratory in Ft. Pierce, Florida, write the article. A slightly edited version follows: 

The rootstock and root system are what make trees strong enough to survive and produce a good crop of high-quality fruit, even when infected with HLB and other stresses.

SuperSour

Among the hundreds of promising new SuperSour hybrid rootstocks being tested within the USDA ARS citrus rootstock breeding program, several have been standout performers in field trials. The trials have been performed at Ft. Pierce, at the USDA Whitmore Farm in Lake County and in grower-cooperator trials at other sites.

Two of these early-standout rootstock performers were released in late 2023 as SuperSour 4 and SuperSour 5 and are being included in some new commercial plantings this year. Some of the other USDA SuperSour hybrids not yet released appear extremely outstanding in field trials. They are producing lush trees loaded with good fruit at 7 to 8 years of age, alongside trees on other rootstocks that appear as the more common weak, diseased trees.

Among the unreleased SuperSour hybrids that appear particularly outstanding is a hybrid between standard sour orange and trifoliate orange, and a similar hybrid that has US-942 as one of its parents. Both of these new SuperSour hybrids exhibit excellent tolerance to HLB and are on the short list for potential release and commercial availability in 2025–26. They are likely to be named SuperSour 6 and 7.

While the outstanding newest rootstocks will not improve performance of existing trees in the field, these new hybrid SuperSour rootstocks provide good hope for the future. They offer the opportunity to re-build a new citrus industry with healthier and more productive trees on the foundation of a much stronger rootstock.

Source: USDA ARS

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