introduction of the first rhizomania resistant sugar beet monogerm hybrid variety (zarghan)

rhizomania (root madness) is caused by beet necrotic yellow vein virus (bnyvv). this disease was first reported fromitalyin 1959 and fromfars,iranin 1996. during the recent years, it has been increasingly developing across the country so that most beet production areas such as khorasan, fars, west azarbaijan,isfahanandkermanshahare now more or less affected by the disease. typically, the taproot remains small and weak and becomes turgid. also, a higher number of hairy roots appear at the end of or along the root. yield reduction due to the disease can be significant. as the cultural practices have proved to be ineffective economically and environmentally, breeding the disease resistant varieties has been paid attention to control the disease and sustain the beet production. the first step in improving the disease resistant varieties is to find the resistant resources among the cultivated and wild germplasms of sugar beet. breeding rhizomania resistant varieties has become a breeding objective of high priority at sugar beet seed institute (sbsi),karaj,iransince 1998. having studied the domestic and foreign germplasms of sugar beet during 1998-2000 at the infected fields of zarghan agricultural research station (fars), sbsi found the resistant resources. a pollinator population was found to be of a higher resistance compared with the other resources evaluated under natural and artificial (glasshouse) infections. therefore, by selecting resistant single plants from this population, the level of resistance increased to a greater extent and a new parent was derived which had, in addition to a high resistance, proper agronomic and technological characters. for this reason, it was selected as the pollinator parent. in 2000, 26 hybrids were derived from two breeding programs among which the above-mentioned tolerant pollinator as well as some other male parents was contained. the resulted hybrids were evaluated in multi-environment trials (met) under diseased and disease-free conditions. in addition to disease resistance of the hybrids, some other traits such as root yield, sugar content and technological characters were also studied in the met trials. the genetic combination of the new hybrid was found to be one of the most successful combinations. the hybrid was also studied in on-farm (demo) trials of the sugar factories during 2004-2006. considering all data obtained from the field replicated and demo trials, the new hybrid variety in infected fields was found to be superior to the all domestic monogerm hybrids such as rasoul, shirin, jolgeh and gadouk developed and released during the recent years. in some instances, its performance was even near to the foreign resistant varieties. taking the importance of rhizomania into account, the development and release of this hybrid will play an important role in gaining self-sufficiency and saving a large amount of money which otherwise has to be spent for importing foreign seeds.   genetic, morphological and agronomic characters of the cultivar zarghan (the first iranian rhizomania tolerant monogerm hybrid)   no character description 1 germity, ploidy and type monogerm, diploid and n-z 2 specific character tolerant to rhizomania 3 root morphology narrow root grooves 4 proper sowing time and growing areas cold areas (late march) and temperate areas (mid-late march) 5 proper harvesting time cold areas (late sept-early oct) and temperate areas (mid-late oct) 6 proper plant density 120000 and 100000 plants/ha in infected and non-infected fields, respectively 7 growing period 180 days 8 nutritional requirement (nitrogen fertilizer) similar to other cultivars in non-infected fields and %25-35 higher in infected fields