The sulphur treatment would significantly reduce the formation of seeds in the Narcodott’s mandarin variety, without affecting the performance
and the quality of the fruit. This is the main conclusion of a survey that was carried out by “ Universitat de Valencia” and “ Universitat Politècnica de València” research staff, with the Serrano Agricultural holdings Company, that was recently published by the “Plus One” journal.
The study is based on a reality that the Narcodott mandarin is appreciated by the fresh market, but it could produce seeds due to the cross-pollination with other varieties. “The customers prefer the mandarins without any seeds, and because of that, the farmers need to develop new techniques that avoid the growth of seeds”, says Alfonso Garmendia, a researcher at the Mediterranean Agroforestry Institute and professor at the School of Agricultural Engineering and Natural Environment (ETSIAMN) of the UPV.
To answer this question, the study has been evaluating the effects of six treatments (ammonium nitrate, potassium nitrate, sulphur, sucrose, methylcellulose, callose) for better knowing which of them would be more efficient and could be used in the future as an agronomical treatment that would avoid the presence of seeds in the mandarines, without showing any negative effects to the performance and quality of the fruit.
Tha main authors of the study emphasize that the project is still in a preliminary phase. “Nowadays the use of sulphure in citrus fruits it`s not allowed, there is no registered product for it. Our study open a new way offering some preliminary data, but it is necessary to keep investigating and improving the formula that will permit to obtein a registered product and with all guarantees of use by farmers” they signal.
Main results achieved
Of the six treatments tested, only the elemental sulphur was able to significantly reduce the number of seeds by 87% compared to the positive control and, in addition, it didn’t affect the yield or the quality of the fruit.
This is a pioneering result, since any product previously tested in fields conditions has obtained the following results. That makes it in a promising applicant for developing treatments that will prevent the presence of seeds in the fruit. The results obtained are the first point of start in order to achieve this goal” says María Dolores from the Valencian Agrodiversity and also teacher of ETSIAM.
Thereby, the team of researchers advocates further research to test, for example, different treatment dosis or its application on other citrus varieties.
“The mechanism by which sulfur blocks pollen tube growth inside the stigmas needs to be better understood. In addition, experiments carried out in semi-real field conditions should be tested and its application to different varieties of mandarins, or even to other citrus fruits such as oranges or lemons, should be explored," says Hugo Merle, professor in the Department of Agroforestry Ecosystems at the UPV.
Finally, the authors emphasize that among the results obtained it was found out that the trees covered with netting, which is a technique used by some farmers, showed the lowest number of seeds per fruit, but also the lowest yield and the smallest fruit diameter. In the same way, the sucrose treatment produced the opposite effect to the sucrose treatment because it increased the number of seeds per fruit.
Francisco García-Breijo, Roberto Beltrán and Nuria Cebrián, also from ETSIAMN, together with José Reig (Cavanilles Institute of Biodiversity and Evolutionary Biology of the University of Valencia) and Carlos Zornoza (Explotaciones Agrícolas Serrano SA) also participated in the study.
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References
Garmendia A, Raigón MD, García-Breijo F, Reig J, Beltrán R, et al. (2022) Agronomic treatments to avoid presence of seeds in Nadorcott mandarin II. Effect on seed number per fruit and yield. PLOS ONE 17(12): e0278934. https://doi.org/10.1371/journal.pone.0278934
