Management of Verticillium Wilt of Avocado Using Tolerant Rootstocks

Abstract

The global avocado industry is growing, and farmers are seeking to expand their plantations. However, many lands suitable for avocado planting were previously cultivated with hosts of the soil-borne fungal pathogen Verticillium dahliae, which is the causal agent of Verticillium wilt (VW). VW can seriously impair avocado orchards, and therefore, planting on infested soil is not recommended. The use of different rootstock types allows avocado cultivation in various regions with diverse biotic and abiotic constraints. Hence, we tested whether genetic variance among rootstocks may also be used to manage avocado VW. Six hundred trees, mostly Hass and some Ettinger, grafted on 23 selected rootstocks were evaluated for five years in a highly V. dahliae-inoculated plot for VW symptoms, fungal infection, and productivity. The selected rootstocks displayed a significant variation related to VW tolerance, and productive avocado rootstocks with potential VW tolerance were identified. Moreover, the rootstock productivity appears to correlate negatively to the susceptibility level. In conclusion, planting susceptible rootstocks (e.g., VC66, VC152, and VC26) in infested soil increases the likelihood of massive tree loss and low productivity. Whereas, tolerant rootstocks (e.g., VC804 and Dusa) may restrict VW and enable avocado cultivation on infested soils.

Highly infested soils undermine the use of resistant olive rootstocks as a control method of verticillium wilt

“…Resistant rootstocks have been successfully applied to control V . dahliae in avocado (Haberman et al ., 2020) and pistachio (Epstein et al ., 2004) in field conditions. The development of new olive material with higher levels of resistance (Arias‐Calderón et al ., 2015; Trapero et al ., 2015) might provide rootstocks that are able to effectively control VWO even under high inoculum potential conditions.…”

“…Therefore, the use of rootstocks as control measure for VWO should not be ruled out as completely ineffective, particularly if it can be applied under conditions of low or moderate inoculum potential and accompanied by an integrated control strategy (López-Escudero and Mercado-Blanco, 2011). Resistant rootstocks have been successfully applied to control V. dahliae in avocado (Haberman et al, 2020) and pistachio (Epstein et al, 2004) tive control of VWO in highly infested soils, and its use should not be considered as a control measure for the disease. Novel genetic material with higher resistance that can be used as a rootstock and completely prevent V. dahliae from reaching the scion is yet to be identified.…”

“…However, rootstocks are extensively used in other fruit crops (Mudge et al ., 2009) and have been successfully applied to control V . dahliae in avocado (Haberman et al ., 2020) and pistachio (Epstein et al ., 2004). For this reason, a few studies have evaluated the use of olive cultivars and wild olive genotypes as rootstocks for controlling VWO with positive results (Hartmann et al ., 1971; Porras‐Soriano et al ., 2003; Colella et al ., 2008; Bubici and Cirulli, 2012; Jimenez‐Fernandez et al ., 2016).…”

“…The main reason is the adaptation capacity and resilience of most cultivars (Barranco, 2017), as well as the lack of understanding of the complexities inherent to the selection and breeding of suitable rootstocks (Cousins, 2005). However, rootstocks are extensively used in other fruit crops (Mudge et al, 2009) and have been successfully applied to control V. dahliae in avocado (Haberman et al, 2020) and pistachio (Epstein et al, 2004). For this reason, a few studies have evaluated the use of olive cultivars and wild olive genotypes as rootstocks for controlling VWO with positive results (Hartmann et al, 1971;Porras-Soriano et al, 2003;Colella et al, 2008;Bubici and Cirulli, 2012;Jimenez-Fernandez et al, 2016).…”

Rootstock-Dependent Response of Hass Avocado to Salt Stress

“…Rootstocks have long been used to help sensitive species cope with biotic and abiotic stresses. With avocado, most research has focused on diseases such as phytophthora root rot [ 8 ], botryosphaeria branch dieback [ 9 ], and verticillium wilt [ 10 ]. Abiotic stresses addressed in rootstock studies include drought [ 11 ], calcareous soil [ 12 ], and salinity [ 13 ].…”