Development of genetically modified citrus plants for the control of citrus canker and huanglongbing

Abstract

Citrus cultivation is challenging due to the plethora of abiotic and biotic stresses faced by the crop. In recent years, production has been severely affected by diseases such as citrus canker and huanglongbing (HLB). Disease management is hampered as there is no field resistance to these diseases in any of the important commercially planted varieties. Traditionally, conventional breeding approaches have been applied for the improvement of the susceptible cultivars; however, this technique is laborious and time consuming. Genetic transformation of citrus allows for the rapid integration of novel genes into the plant's genome to develop disease-resistant transgenic plants. Therefore, efforts have been made to utilize genetic engineering tools to develop genetically modified citrus that are resistant to citrus canker and HLB. This review summarizes the major achievements made in the development of citrus canker and HLB tolerance using transgenic technologies.

Transgenic Sweet Orange Expressing the Sarcotoxin IA Gene Produces High-Quality Fruit and Shows Tolerance to ‘Candidatus Liberibacter asiaticus’

“…Taken together, genetic transformation to overcome disease threats is a laborious and time-consuming solution for long-term perennial crops such as citrus, and must include different sources of tolerance/resistance inducers, in order to prevent a mutation in the pathogen [ 89 ]. However, concerns are still widespread among the community regarding the commercial cultivation of “genetically modified crops”, even under scientific evidence that the improved crop is safe while increasing resistance against biotic and abiotic stressors, yield, and nutritional quality, besides reducing environmental harm [ 90 ].…”

Huanglongbing Pandemic: Current Challenges and Emerging Management Strategies

“…The overexpression of the FLS2 protein causes the reduction in susceptibility to Xcc. The FLS2 protein is also present in the sweet orange citrus but has very low homology to the known functional FLS2 isoforms, which may be the reason for the lack of a defense response [ 283 ]. The grapefruit citrus plants expressing FLS2-1 and FLS2-2 have increased the expression of the defense-related genes WRKY22, GST1, and EDS1 [ 283 ].…”

Housekeeping genes selection for gene expression on Citrus sinensis infected with CLas or CTV using RT-qPCR

“…Sin embargo, este aparente equilibrio puede ser temporalmente alterado con introducción de nuevas razas, desbalances inducidos por factores climáticos y microbiológicos, como es el caso del reciente brote reportado en el centro de Veracruz (Martínez-Bustamante et al, 2020). La dificultad de controlar estos patógenos con estrategias convencionales (Mora-Aguilera et al, 2014a;Loeza-Kuk et al, 2011), y la necesidad de producir materiales genéticos resistentes en menor tiempo posible (CTV) o ante la ausencia de fuentes de resistencia viables para estos patógenos (CLas), propició en los 90's la obtención exitosa de cítricos transgénicos, primero en CTV y posteriormente en CLas (Soares et al, 2020;Loeza-Kuk et al, 2011;Gutiérrez-Espinosa et al, 1997). Sin embargo, regulaciones de bioseguridad ha limitado su implementación comercial.…”

“…The difficulty of controlling these pathogens with conventional strategies (Mora-Aguilera et al, 2014a;Loeza-Kuk et al, 2011), along with the need to produce resistant genetic materials in the least time possible (CTV) or the lack of feasible resistance sources against these pathogens (i.e. CLas) led to successfully obtain transgenic citrus material in the 1990's, first on CTV and later on CLas (Soares et al, 2020;Loeza-Kuk et al, 2011;Gutiérrez-Espinosa et al, 1997). Nevertheless, biosafety regulations have limited their extensive commercial implementetion.…”