Transgenic groundnut with resistance to fungal pathogens (Foliar diseases of Groundnut)

Abstract

The late leaf spot (LLS) disease caused by Phaeoisariopsis personata (Berk. And Curt.) Van Arx, and rust caused by Puccinia arachidis Speg. are economically important foliar fungal diseases of groundnut (Arachis hypogaea L.). The annual losses caused by LLS and rust are over US$ 599 m and US$ 467 m, respectively. The development of groundnut germplasm with durable resistance to these fungal pathogens would provide the most effective and viable option for crop improvement. Here we report enhanced fungal resistance in groundnut by introducing a constitutively expressed rice chitinase gene (Rchit) with anti-fungal properties that have been shown to play significant role in plant defense by degrading the chitin of fungal cell walls. Over 75 independently transformed transgenic events were developed with the popular groundnut varieties JL 24, ICGV 89104 and ICGV 86031 through Agrobacterium -mediated genetic transformation by using the cotyledon explants from mature imbibed seeds. The transgenic plants were characterized at the molecular level for gene integration, copy number and expression of the transgene. Several transgenic events showed about 2- to 14-fold higher level of chitinase activity than the untransformed controls. The transgenic events showing high level of chitinase activity were selected for in vitro seed colonization with A. flavus. Seeds of transgenic events showing 0-10% A. flavus infection were advanced to subsequent generations and fungal bioassays for late leaf spot and rust were carried out using detached leaf technique. Results revealed an increased incubation period and latent period and a lower infection frequency (50-100% reduction in disease incidence) indicating a varying level of resistance in the selected transgenic plants as compare to the untransformed controls. The selected transgenic events thus identified will be used for further field evaluations and if confirmed, as resistance sources to develop groundnut varieties with enhanced resistance to the foliar fungal pathogens and A.