Age-related resistance to Fusarium oxysporum f. sp. cepae and associated enzymatic changes in seedlings of Allium cepa and A. fistulosum

Abstract

This research analysed the response of onion (Allium cepa) and A. fistulosum against Fusarium oxysporum f. sp. cepae (Foc) isolates and the associated changes in peroxidase, β-1,3-glucanase and chitinase activities. The response of A. cepa and A. fistulosum at different stages of seedling development were also evaluated. Several seedling tests were performed, and disease symptoms were evaluated 12-14 days after inoculation. Allium fistulosum behaved as more resistant than A. cepa cultivars by exposition to the most aggressive Foc isolates at sowing date. Increased levels of peroxidase and glucanase activities were found in the A. cepa and A. fistulosum seedlings exposed to the pathogen, and were positively correlated with disease symptoms. For chitinase activity, this correlation was found only for A. cepa. Two peroxidase isoforms were found to be specific for A. fistulosum roots after inoculation and could be involved in resistance. The inoculation at 7, 14 and 42 days after sowing showed that both host species were resistant to Foc, proving that onion susceptibility decreased promptly after germination. However, an increase in peroxidase and glucanase activities in 7-and 14-day-old inoculated seedling was detected only for A. cepa, suggesting an earlier acquisition of resistance in A. fistulosum.

Fusarium basal rot: profile of an increasingly important disease in Allium spp.

“…In early stages of germination, the infection results in a delay of seedling emergence (Gutierrez and Cramer 2005;Gutierrez et al 2006) or damping-off of the seedlings (Fig. 1f) (Galeano et al 2014;Kintega et al 2020;Saxena and Cramer 2009). Fusarium pathogens also cause a loss of transplanted seedlings (Fig.…”

“…Seedling age and growth stage have been proposed as major determinants of FBR presence on Allium spp. (Cramer 2000;Galván et al 2008;Galeano et al 2014). FBR tends to be more aggressive when infection establishes at an early stage of seedling development and on mature bulbs in storage (dormant bulbs) (Retig et al 1970;Stadnik and Dhingra 1997;Cramer 2000;Taylor et al 2013;Galeano et al 2014).…”

“…(Cramer 2000;Galván et al 2008;Galeano et al 2014). FBR tends to be more aggressive when infection establishes at an early stage of seedling development and on mature bulbs in storage (dormant bulbs) (Retig et al 1970;Stadnik and Dhingra 1997;Cramer 2000;Taylor et al 2013;Galeano et al 2014). Similarly, disease aggressiveness is also affected by the age of transplants, where older transplants might show no symptoms even though pathogenic fungi can still be recovered from them (Stadnik and Dhingra 1997).…”

Breeding onion for resistance to Fusarium basal rot: comparison of field selection and artificial inoculation

“…However, the detected tendency of lower FBR rates in PFC suggests that this strategy is suitable and successful in a long term approach. Should FBR resistance trait be influenced by growing conditions (Apaza and Mattos 2000;Cramer 2000;Galeano et al 2014;Galván et al 2008;Rout et al 2015), selection during field and storage stages requires an additional integrated approach to follow, which includes variables like vigor, root emission and overall health status. Commercial features must also be considered, all of which determine a comprehensive but consequently slow advance in developing FBR resistant cultivars.…”

“…Some authors state that the resistant phenotype would rely upon several minor genes or QTLs (Apaza and Mattos 2000;Cramer 2000;Marzu 2015;Saxena and Cramer 2009), while recent studies suggest that FBR resistance is conferred by one dominant gene (Marzu 2015). Different factors such as plant vigor (Apaza and Mattos 2000;Cramer 2000), plant age (Galeano et al 2014) and possibly the root emission rate (Galván et al 2008;Rout et al 2015) may influence the expression of the trait. In general, two major processes are postulated to be involved in resistance, as plant responses to the infection.…”