Introduction of BLYV resistance to 3-way crossed F1 generation by resistant pollen parent.

Abstract

Beet leaf yellowing virus (BLYV) causes yellowing of sugar beet leaves and decrease about 30% of sugar yield in severe case. The virus incubates in weeds and green peach aphid (GPA) spread the virus to sugar beet. It is difficult that extermination of the virus and the vector, so utilization of the resistance to BLYV is attracting attention. It is known that Beet western yellows virus (BWYV) resistant genetic resources which were published by USDA also have resistant to BLYV. Our group doing breeding of pollen parents and seed parents using the genetic resources.

Sugar beet cultivar is generally 3-way crossed F1 generation, so their half of genetic background is derived from pollen parent. If the resistance has dominant effect, we can easily introduce BLYV resistance to cultivar from pollen parent. In this research, we report the resistance test result of 3-way crossed F1 materials whose pollen parent is BLYV resistant.  In 2021, we tested 6 standard materials and 16 3-way crossed F1 materials which were derived from 2 BLYV resistant pollen parents. In 2022, we tested 6 standard materials and 17 3-way crossed F1 materials which were derived from 7 BLYV resistant pollen parents. The virus was inoculated to sugar beet seedlings by GPA. The seedlings transplanted in the field. The field design consisted of 4 replication whose plant number was 5. In 2021, non-inoculated field also made as same design. In 2021, we evaluated yellowing symptom of inoculated plants and compared yield between inoculated plots and non-inoculated plots. In 2022, we evaluated yellowing symptom of inoculated plants.  For evaluation of yellowing symptom, we defined 10-level Yellowing Index (YI). YI 0.0 means no-symptom, YI 3.0 means the severest symptom. For evaluation of decrease of yield, the weight of root and crown, Brix were measured.  Yellowing evaluation was done at 2021/8/31, 2022/8/17, harvest day was 2021/10/25.  In 2021, YI, reduction rate of root and crown weight and Brix of the “Strong” resistant standard lines were 0.0-0.1, 6.2-6.6%, 1.1-5.3%, those of the “Medium” resistant standard lines were 0.0-0.1, 6.2-6.6%, 1.1-5.3%, those of the “Weak” resistant standard lines were 2.1-2.7, 43.7-58.9%, 13.4-13.9%, those of 3-way crossed lines were 0.1-0.6. 20.5-36.9%, 5.8-9.8%. In 2022, YI of the “Strong” resistant standard lines were 0.4-0.2, those of “Medium” resistant standard lines were 1.1, those of “Weak” resistant standard lines were 1.9-2.2, those of 3-way crossed lines were 0.4-0.9.  From this research, using BLYV resistant pollen parent, introduce of resistance to 3-way crossed generation and reduction of yield decrease were succeeded. The resistance shows dominant effect, so introduction of BLYV resistance by resistant pollen parent can be promising methods.  This research was supported by the research program on development of innovative technology grants from the Project of the Bio-oriented Technology Research Advancement Institution (BRAIN).