The Australian finger lime, a citrus relative, could be a new specialty crop for Florida citrus growers.
Traditionally, finger limes have remained rare in the United States, grown few and far between. However, the fruit’s unique tolerance to HLB is becoming increasingly attractive to Florida growers. Manjul Dutt, research assistant scientist at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) believes finger limes could secure Florida’s position in the global citrus market.
In the field, finger limes have a low HLB infection rate. Early on, researchers noticed these trees were much more tolerant to HLB than any of the traditional citrus varieties being grown in the state.
“We have a number of theories as to why this finger lime could be tolerant to HLB,” Dutt says. “It could be due to the presence of physical barriers, or it could be due to the presence of certain toxins or certain chemicals in the phloem that the Candidatus Liberibacter asiaticus’ (CLas) doesn’t like.” CLas is the bacterium that causes HLB.
The young flesh of finger limes contains high levels of anthocyanins, producing a dark-red color on the leaves of the tree. Studies have indicated that insects, including the Asian citrus psyllid, move according to visual cues. It’s possible the high levels of anthocyanins can discourage psyllid feeding and thus prevent transmission of HLB.
Additionally, the phloem of the finger lime contains high levels of aldehyde compounds. According to Dutt, citronellol, a compound of growing interest and present in the phloem, has shown to have anti-bacterial activity, which could also be preventing the replication of CLas.
One of the pressing issues limiting commercial production of finger limes in Florida is the lack of knowledge about the crop. Dutt and his team of researchers are currently evaluating different rootstocks in hopes of finding varieties suitable for Florida’s growing conditions.
Furthermore, they are developing new cultivars that are crosses between conventional citrus and finger limes to incorporate HLB tolerance into traditional citrus varieties. Dutt says thousands of trees are currently being evaluated and quite a few appear promising.
This interview with Dutt is featured in the February 2021 episode of the All In For Citrus podcast, a joint project of UF/IFAS and AgNet Media. Listen to the full podcast here.