Physical methods to reduce the inoculum of Sclerotium cepivorum in purple garlic seed (Allium sativum L.)

Abstract

Introduction. In Colombia, garlic production is affected by pathogens, mainly Sclerotium cepivorum, which is disseminated by planting material. It is necessary to establish low-cost technologies to control this pathogen. Objective. To evaluate two thermotherapy methods, dry heat thermotherapy and water immersion thermotherapy, to reduce the presence of S. cepivorum in garlic seed and its effect on agronomic characteristics of plants emerged from treated bulbs. Materials and methods. This work was carried out at the Tibaitata Research Center of Corporacion Colombiana de Investigacion Agropecuaria (AGROSAVIA), located in Cundinamarca, Colombia, during the first semester of 2019. Nine treatments were evaluated; five in dry heat thermotherapy: 35 ºC for 12 h, 35 ºC for 129,6 h, 50 ºC for 48 min, 5 ºC for 20 days, 38 °C for 1 h; two in hot water immersion thermotherapy:48 °C for 30 min, 50 °C for 20 min, and two controls: chemical disinfection (tebuconazol) and room temperature (20 ºC for 20 days) in a randomized complete block design. Sprouting of bulbs and growth of garlic plants after applying thermotherapy to the seed and viability of S. cepivorum sclerotia were evaluated. Results. Seed storage at 5 ºC for 20 days accelerated its sprouting, reached a 80 % germination after five days, increased leaf number and biomass accumulation. Sclerotia germination was between 33 and 67 %; the treatment that presented the lowest incidence was 35 ºC for 129,6 h (33 %). Conclusion. Dry heat thermotherapy treatment at 35 °C for 129,6 h showed potential in reduction of S. cepivorum inoculum in garlic seeds.