Physiological tolerance of shallot varieties to airborne salinity in coastal sandy soils

Shallot as a horticultural crop has various benefits and important uses as a provider of nutritional needs. Its uniqueness in aroma and flavor makes it commonly used as a seasoning so that it has a good economic value as an increase in farmers’ income. Sandy land on the coast has the potential for shallot cultivation. The presence of wind that airborne salinity on coastal land requires the selection of tolerant varieties and knowledge of the level of airborne salinity concentration that shallot plants can tolerate. Experiments have been conducted from July to December 2023 in the screenhouse and horticultural agronomy lab, Faculty of Agriculture, Jenderal Soedirman University, Purwokerto (7°24’27.7”S, 109°15’19.1”E). Treatments consisted of the use of shallot varieties Bali Karet (B1) and Bima Brebes (B2), with the application of several concentrations of airborne salinity consisting of 0, 6, 12, and 18 mS cm-1. The Bali Karet variety excels in plant height and root dry weight morphologically. Physiologically, Bima Brebes has higher levels of chlorophyll a and stomatal density, while Bali Karet is superior in chlorophyll b. Harvest results show Bima Brebes produces more tubers, while Bali Karet produces higher fresh tuber weight per clump. Morphological parameters (plant height, root dry weight), physiology (chlorophyll a, chlorophyll b, stomatal aperture, stomatal density), and yield showed the highest value at the lowest air salinity concentration (0 mS cm-¹). Both varieties increased proline as a tolerance mechanism to 18 mS cm-¹ air salinity. The best interaction occurred between Bali Karet and 0 mS cm-¹ salinity on stomatal opening, and between Bima Brebes and 0 mS cm-¹ salinity on stomatal density. Both varieties were classified as having moderate tolerance to 18 mS cm-¹ salinity, but total chlorophyll was very sensitive to this salinity concentration.