Physiological and sanitary quality of castor oil plant seeds due to ultraviolet-C radiation

Abstract

Castor oil plant is a very important crop, known worldwide for its seed oil quality. However, the crop shows serious issues with pathogens that may affect seed quality. Thus, this study aimed to evaluate the Ultraviolet-C (UV-C) radiation effects on the physiological and sanitary quality of seeds of two castor oil plant cultivars (Agima and Tamar). We used a completely randomized design in a 2 × 5 factorial scheme with four replicates. The treatments consisted of two castor oil plant cultivars: Tamar and Agima and five UV-C radiation doses: 0 – control; 10.4; 20.7; 31.1; 41.4 kJ m−2. To characterize the physiological and sanitary qualities of the seeds, we performed moisture content, germination, first counting, accelerated aging, electrical conductivity, radicle and hypocotyl length, dry mass of radicle and hypocotyl and sanity test (Blotter test). The 41.4 kJ m−2 dose of UV-C radiation reduced the incidence of Aspergillus spp. Fungus in 44.8 and 100% for Agima and Tamar, respectively. However, it has caused a reduction in the physiological quality of both cultivars. The dose of 20.7 kJ m-2 resulted in the germination increase in 66% for Agima and 50% for Tamar. Thereby, the dose 20.7 kJ m-2 provided better physiological quality results of Agima and Tamar, presenting better germination (93 and 86%, respectively), accelerated aging (43 and 65% respectively), radicle length (5.5 and 5.2 cm, respectively), hypocotyl length (1.5 and 1.7 cm, respectively), and lower electrical conductivity (54.2 and 45.2 μS cm-1 g-1, respectively). UV-C radiation can be used to better physiological and sanitary quality results of castor oil plant seed up to the dose of 20.7 kJ m−2, from which UV-C radiation negatively influences seed vigor.