Agronomic treatments to avoid presence of seeds in Nadorcott mandarin II. Effect on seed number per fruit and yield

Nadorcott is a well-established and appreciated mandarin by the fresh market. However, it produces seeds due to cross-pollination with other compatible varieties, which is quite frequent in most producing countries. Consumers prefer seedless mandarins and, therefore, citrus growers need techniques to avoid seeds forming. This study aims to evaluate the effect of six treatments (ammonium nitrate, potassium nitrate, sulfur, saccharose, methylcellulose, callose) on seed number per fruit when applied to Nadorcott trees. In this way, we evaluate which of them is more efficient and can be used in the future as an agronomic treatment to avoid seeds in mandarins. The effect of treatments on yield and fruit quality is also reported. To fulfill this main objective, a randomized complete block design experiment with three applications at flowering was performed on trees. Of the six tested treatments, only elemental sulfur was able to significantly reduce seed number by 87% compared to the positive control. This is a very novel result because it is the first time that such an effective treatment has been found. The biggest seed number per fruit was obtained for the saccharose treatment. Treatments did not significantly influence yield or fruit quality. These results are entirely consistent with a previous study that evaluated the effect of the same products on pollen tube growth, and they can help to develop new techniques. Nevertheless, more studies are necessary to test, for example, different treatment doses.