Combining thermotherapy with meristem culture for improved eradication of onion yellow dwarf virus and shallot latent virus from infected in vitro‐cultured shallot shoots

Abstract

The present study described a combining thermotherapy with meristem culture for improved eradication of onion yellow dwarf virus (OYDV) and shallot latent virus (SLV) from co-infected in vitro-cultured shallot shoots. In vitro-cultured shoots infected with OYDV and SLV were thermo-treated at a constant temperature of 36 C for 0, 2 and 4 weeks, and then meristems (0.5 mm) containing 1-2 leaf primordia were excised and cultured for shoot regrowth. Meristem culture without thermotherapy produced much higher levels of survival (100%) and shoot regrowth (55%) than those (62% survival and 32% shoot regrowth) produced by the procedure combining 4 weeks of thermotherapy with meristem culture. However, much higher virus-free frequencies (70% for OYSV, 80% for SLV and 50% for both viruses) were obtained in the latter than those (10% for OYSV, 15% for SLV and 10% for both viruses) obtained in the former. Histological and subcellular studies showed that thermotherapy imposed stress or damage to the cells of meristems, thus resulting in reduced meristem survival and shoot regrowth. Studies on virus location revealed considerable alternations of virus distribution patterns in the thermo-treated meristems. The results of histological and subcellular studies and analysis of virus distribution pattern added valuable experimental data in the combining thermotherapy with meristem culture for virus eradication. These data provided explanations as to why combining thermotherapy with meristem culture improved the eradication of OYDV and SLV from the virus-infected in vitro shallot shoots.

Phytotoxicity and Other Adverse Effects on the In Vitro Shoot Cultures Caused by Virus Elimination Treatments: Reasons and Solutions

“…aggregatum , 10603) was free from Onion yellow dwarf virus (OYDV) and Shallot latent virus (LSV), without thermotherapy, respectively. After heat treatment, 66% and 73% of the 0.5 mm meristematic region became free of those viruses, respectively [ 116 ]. Effectiveness of thermotherapy can be affected by virus type and the host genotype.…”

“…Moreover, decreased nucleo/cytoplasma ratio induced by heat treatment was also detected in shallot ( Allium cepa var. aggregatum G. Don, 10603) [ 116 ].…”

“…In general, regeneration rates are lower than survival rates. The meristems of onion plants survived 100%, and only 55% regenerated in the control treatment (without thermotherapy), while meristems from heat treated (at 36 °C) plantlets for four weeks survived and regenerated at a rate of 62% and 32%, respectively [ 116 ].…”

“…aggregatum G. Don, 10603) decreased significantly as the duration of treatment (36 °C) increased from zero to four weeks; 85% of the plants survived the two-week-long treatment, and 51% of the meristems regenerated shoots. Survival rates were 62% in four weeks of treatment, and only 32% of meristems were able to regenerate shoots [ 116 ]. By increasing the duration from three to seven weeks of treatment at 37 °C, the survival rate of in vitro apricot ( Prunus armeniaca L.) shoots was reduced.…”

Double‐edged effects of the cryogenic technique for virus eradication and preservation in shallot shoot tips

“…It has been reported that combining thermotherapy with cryotherapy proved to be the most efficient for elimination of OYDV, LYSV, and garlic common latent virus from garlic (Vieira et al, 2015). However, studies on virus elimination from shallot plants are limited (Putri et al, 2019;Wang et al, 2021).…”