Zazao, a new early-maturing and high-quality chestnut cultivar

Zazao 2 is a new early-maturing and high-quality chestnut cultivar bred by crossing Yang 5 with Yanshanzaofeng at Changli Institute of Pomology, Hebei Academy of Agricultural and Forestry Sciences. Artificial hybridization was carried out in 2002, and seedlings obtained in 2003. From 2005 to 2007, one of the seedlings was identified as a key superior plant in the evaluation process. Since 2008, regional tests have been carried out in Kuancheng County, Xinglong County, Qianxi County of Hebei Province with grafted plants. The test confirmed that the agronomic traits of early maturity, good nut quality and strong stress resistance of this cultivar are genetically stable. The cultivar is a deciduous tree, with medium plant growth potential, upright tree posture and compact crown. The germination rate of biennial bearing branch was 60.1% and the proportion of bearing branches was 45.3%. The bearing branch with few hairs is long branch type, with an average length of 40.16 cm, a diameter of 0.77 cm, and an internode length of 1.62 cm. The average number of bearing shoots on each biennial bearing branch is 2.35, and each bearing branch bears an average of 2.65 burs; the average bur weight is 58.56 g; each bur contains 2.75 nuts; the average single nut weight is 8.22 g. It began to bear fruit in the second year after grafting, and entered the full production period in the fourth year, with average yield of 4030 kg · hm- 2 . The leaf is medium in size, with an average length of 18.16 cm. It is dark green, oval, with acuminate leaf tip, wedge- shaped leaf base, yellow- green petiole, serrated leaf margin, and outward serrated. The length of catkin is about 18.02 cm, and the numbers of catkin on each biennial bearing branch is 11.6. The burs is ellipsoid, with densely and large angled bur spines; the bur is green when mature and the cracking mode is a glyph crack or petal crack. The nut is ellipsoid, purple brown, and bright, and the average single nut weight is 8.22 g. The kernel is yellow, fine, containing 47.83% water, 0.86% fat, 22.96% total sugars, 52.15% starch 7.22% protein and 32.15 mg∙100 g-1 vitamin C; the quali- ty of nuts is excellent. Zazao 2 matures in late August. The tree has strong resistance to chestnut red spider, chestnut borer and chestnut blight, as well as to drought, cold and low fertility. Therefore, it is suitable for planting in barren river beaches, plain sandy soils and mountains (with gneiss, shale and granite soils). The plant spacing recommended is 4 m × 4 m. The appropriate pollinizers include Yanshanzaofeng, Yanjin, Yanguang, and Bailuxiang. The cultivar is suitable for training the natural open center system. The new branches of young trees grow vigorously, and branch bending and bud carving, which can achieve early bearing and high yield is highly recommended. For mature trees, attention should be paid on the cultivation and rejuvenation of the bearing branch group, and adopt the technology of alternate renewal and crown control pruning.