The Road to Resistance in Forest Trees

Abstract

In recent years, forests have been exposed to an unprecedented rise in pests and pathogens. This, coupled with the added challenge of climate change, renders forest plantation stock vulnerable to attack and severely limits productivity. Genotypes resistant to such biotic challenges are desired in plantation forestry to reduce losses. Conventional breeding has been a main avenue to obtain resistant genotypes. More recently, genetic engineering has become a viable approach to develop resistance against pests and pathogens in forest trees. Tree genomic resources have contributed to advancements in both these approaches. Genome-wide association studies and genomic selection in tree populations have accelerated breeding tools while integration of various levels of omics information facilitates the selection of candidate genes for genetic engineering. Furthermore, tree associations with non-pathogenic endophytic and subterranean microbes play a critical role in plant health and may be engineered in forest trees to improve resistance in the future. We look at recent studies in forest trees describing defense mechanisms using such approaches and propose the way forward to developing superior genotypes with enhanced resistance against biotic stress.

The role of rhizodeposits in shaping rhizomicrobiome

“…It is well known that plants actively recruit beneficial microorganisms to defend against phytopathogens (Rudrappa et al ., ; Mendes et al ., ; Edwards et al ., ; Raaijmakers and Mazzola, ; Durán et al ., ). The classic examples of beneficial microbe recruitment by plants are Rhizobia and Mycorrhiza attracted to plant roots to establish a symbiotic relationship with the plants (Peters and Long, ; Bais et al ., ; Besserer et al ., ; Liu and Murray, ; Naidoo et al ., ). Among different components of rhizodeposits, root exudates constitute the biggest portion and have the most diversified nutritional composition when compared with other rhizodeposit components.…”

eCALIBRATOR: A Comparative Tool to Identify Key Genes and Pathways for Eucalyptus Defense Against Biotic Stressors

“…This is believed to be due to the lack of water movement through the process of transpiration. Knowledge of the defense responses induced upon the pest or pathogen challenge can aid in the development of strategies to improve tree defenses and select for more resistant tree genotypes (Naidoo et al, 2019).…”

Endophyte inoculation enhancesUlmus minorresistance to Dutch elm disease

“…by proteases or chitinases, which are able to degrade the hyphal cell wall of pathogens (Guthrie and Castle, 2006;dos Reis Almeida et al, 2007;Orlandelli et al, 2015). Indirectly, endophytes can stimulate the defence response of the plant by altering different signal transduction pathways, sometimes related with jasmonic or salicylic acid signalling (Shoresh et al, 2010;Fesel and Zuccaro, 2016;Martínez-Medina et al, 2017;Khare et al, 2018;Naidoo et al, 2019). Some endophytes enhance plant growth by synthesizing gibberellins (e.g.…”