Genes for parasite-specific, nonhost resistance in populus

Area of Science:

• Plant pathology
• Genetics
• Evolutionary biology

Background:

• Nonhost resistance is a plant's innate ability to resist pathogens that do not typically infect it.
• This resistance is often considered non-specific, but its genetic basis, especially for specialized parasites, is not fully understood.
• Understanding the genetic sources of nonhost resistance is crucial for developing disease-resistant crops.

Purpose of the Study:

• To investigate the genetic basis of nonhost resistance in interspecific hybrid poplars.
• To determine if resistance to specific fungal pathogens is inherited from native or non-native parent species.
• To identify the role of major genes in conditioning parasite-specific nonhost resistance.

Main Methods:

• Created two interspecific hybrid poplar pedigrees (Populus trichocarpa x P. deltoides and P. trichocarpa x P. maximowiczii).
• Planted pedigrees in a common garden to expose them to native parasites of P. trichocarpa.
• Analyzed segregation of resistance to Venturia inopina and a Taphrina sp. fungi.

Main Results:

• Monogenic and oligogenic resistance to the two fungal pathogens segregated in a parasite-specific manner.
• Resistance genes were not inherited from the native P. trichocarpa parent.
• Resistance was inherited from the allopatric, nonhost congeners, P. deltoides and P. maximowiczii.

Conclusions:

• Major genes confer parasite-specific nonhost resistance in poplars.
• Resistance originates from non-native relatives, challenging the notion of solely non-specific defense.
• The evolutionary maintenance of these specific resistance genes remains an open question.