Sustainable late blight management: Evaluating the success of 3 R- gene potatoes in Bangladesh

Most. Mahbuba Begum1, M. Madhobi1 , S. Halder1 , M. Khatum1 , D. Douches2 , and Phillip S. Wharton3. 1 Bangladesh Agricultural Research Institute (BARI), Biotechnology Division Gazipur-1701, Bangladesh. 2 Michigan State University, USA. 3 University of Idaho, USA

Background:

Bangladesh is the seventh largest potato producer in the world and third in Asia after China and India. Late blight of potato caused by the fungus Phytophthora infestans is the most important disease in Bangladesh that can result into crop failures in a short period and consequently reduced the yield. The USAID Feed the Future Biotechnology Potato Partnership has developed bio-engineered potatoes with 3 R-gene late blight resistance. These genes are naturally found in several Solanum spp. To study the efficacy of this Rpi-gene stack (Rpi-blb2, Rpi-vnt1, and Rpi-mcq1) in the variety Diamant, a randomized complete block variety x fungicide, confined field trials (CFT) were carried out at two locations in Gazipur and Rangpur during the 2023-24 growing season. In these trials Diamant 3 R-gene late blight resistant lines were compared to non-genetically modified Diamant varieties in fungicide sprayed and non-sprayed plots. Late blight ratings began upon symptom appearance in non-sprayed control plots, continuing weekly until harvest. No late blight foliar infection was observed in 3 R-gene plots, indicating complete resistance to P. infestans strains in two trials. This data, combined with regulatory information, will be used for the development of dossiers to be submitted to the national biosafety authority in Bangladesh for commercial release of the 3 R-gene potato.

PARTNERS:

• Bangladesh Agricultural Research Institute (BARI): The BARI is a National Research Institute of agricultural crops in Bangladesh. All research activities under this projected implemented by the Scientists of BARI.
• Farming Future Bangladesh (FFB): The FFB is an International NGO and working with us for extension, knowledge and capacity building, media professionals and training.
• University of Idaho, USA: The University of Idaho also working with BARI Scientists for pathological research purpose and genotypic study of pathogen.
• Michigan State University (MSU): The MSU also working with BARI Scientists for research purpose, handled the minituber and also the fund from USAID.
• USAID (United States Agency for International Development): Donated fund for this project.

Results:
1) Evaluation of 3R gene LB events against late blight at CFT Gazipur

Artificial inoculation by Phytophthora infestans showed that the resistant events namely UB015 and UB255 were completely resistant to P. infestans (Fig. 1 a,b & c)). After 7 days of natural infection, the symptoms actively increased only on the check Diamant in non-fungicide spray plot and rapidly increased with time and at 30 days after incubation the whole canopy was almost 100% infected by late blight. Diamant in fungicide spray plot and UB015 and UB255 under both fungicide and non-fungicide spray plots were completely free of P. infestans infection. There was no significant difference in yields between the 3 R-gene lines and non-GM Diamant in sprayed plots. There was a significant difference between 3 R-gene lines and non-GM in the non-sprayed plots (Fig. 2).

 

 

 

 

2) Evaluation of 3R gene LB events against late blight under  at CFT Rangpur 

Results:

The 3R gene LB events namely UB015 and UB255 also performed better than the check Diamant against late blight under natural field conditions at CFT Rangpur. UB015 and UB255 showed complete resistance to Phytophthora infestans [Fig. 3 (a,b&c) ]. The planting date  was on 25 Nov., 2023 at Rangpur and the weather condition was favorable  for late blight initiation on Rangpur. The symptoms observed on 15 Jan.2024 only on the check Diamant in non-fungicide spray plots and gradually increased with time and at 30 days after infection the whole canopy of all tested lines was 96% destroyed by late blight, but UB015 and UB255 were completely free from the infection of  Phytophthora infestans under both fungicide spray and non-spray plots. There was no significant difference in yields between the 3 R-gene lines and non-GM Diamant in sprayed plots. There was a significant difference between 3 R-gene lines and non-GM in the non-sprayed plots (Fig. 4).

 

 

 

 

 

Lessons Learned: Late blight disease caused by Phytophthora infestans  is a major constraints for potato farmers in Bangladesh. To control late blight, farmers commonly use fungicides with high doses and frequencies and consequently reduce farmers family income and pose risk to humans and the environment pollution. The 3 R-gene stack was able to provide complete resistance to infection by the P. infestans strains present in Bangladesh. Therefore, UB015 and UB255 become popular start from the northern part of Bangladesh to farmers and seed potato growers to overcome losses due to disease and fungicide expenses and farmers exposers to harmful chemicals.