Torbat, a New Sugar Beet Monogerm Hybrid Variety Tolerant to Rhizomania Viral Agent and Suitable for Growing in Northeastern of Iran

Beet necrotic yellow vein virus (BNYVV) or rhizomania is one of the most important and destructive diseases of sugar beet (Beta vulgaris L.) in the world. This disease is considered as a limiting factor of sugar beet production in Iran such as Khorasan, Fars, West Azerbaijan, Isfahan and Kermanshah. In order to develop of resistant variety, as simple and easy methods for disease control, a germplasm carrying the Rhizomania resistant gene was incorporated into the selection program in 2002. At harvest, desirable single plants were selected and S1 seeds were produced from each individual plant under cage in 2003. In 2004, each S1 family was test-crossed with a monogerm male sterile female. In 2006, yield trials conducted in a disease nursery in Fars province showed that a hybrid SB37×SHR02-P.4 was superior. This hybrid, coded as SBSI006, was further evaluated in naturally infected fields for disease resistance and root yield during 2008-2012. Results of combined analysis showed that the above-mentioned hybrid with a root yield of 76.12 t/ha was significantly different from the susceptible (Jolgeh, 41.08 t/ha) and recently developed tolerant (Zarghan, 49.12 t/ha) check varieties. The relative superiority of this hybrid as compared to the domestic varieties Zarghan and Pars in yield trials conducted in the field of sugar factories as well as research-extension fields of Khorasan province and also the frequency of disease resistance genes in 70% of the plants of this hybrid makes the hybrid suitable for the northeastern part of the country, considering that the disease agent has a high genetic variation in Great Khorasan province. The hybrid is a diploid monogerm variety tolerant to Rhizomania disease and is suitable for spring sowing. The growing period of this variety is 180 days with the most suitable sowing date being late March. The optimum plant density of the variety is recommended to be 120000 plants per hectare.