选育依据和选育目的我州春季养蚕主要与桑叶开放的早晚和蚕成熟度的快慢程度有关。一般五月底和六月初催青、六月饲育,七月初收茧。春季若适当提早养蚕,既能避开农忙矛盾,又能相对地提高蚕茧的产量和质量。因此,要在一年养好两季蚕,增加蚕茧,提高收入,迫切需要解决早生优质桑品种。一些农村,特别是私人养蚕户,随着生产的发展,也都反映现行当家品种秋雨桑,发芽迟、叶片成熟不齐,叶质较差,特别不利于养春蚕,而且小蚕期稚蚕发育不齐,出现较多的小蚕等。针对这种情况,我们重点以早生丰产、抗病目标,选育出适合于本地区比秋雨桑优异的春蚕和稚蚕用新品种——延桑59。 Breeding basis and breeding purposes Spring sericulture in our country mainly with the mulberry leaf opening sooner or later and the degree of silkworm maturity degree of speed. General end of May and early June to promote youth, feeding in June, early cocoon closed in early July. If early spring sericulture appropriate, not only avoid contradictions but also relatively improve the yield and quality of cocoons. Therefore, it is necessary to raise two seasons of silkworms in one year, increase cocoons, and increase incomes. There is an urgent need to address the early generation of high quality mulberry varieties. In some rural areas, especially private sericulture households, with the development of production, they all reflect the current autumn varieties such as autumn mulberry, late germination, uneven leaf development, poor leaf quality, especially detrimental to spring silkworms, Alzheimer’s disease, there are more small silkworm and so on. In response to this situation, we focus on early harvest, disease resistance objectives, breeding for the region superior autumn mulberry silkworm and new varieties of silkworms - Yan Sang 59.