Breeding report of a new avocado cultivar Tenglong

Persea americana Mill. is an important tropical and subtropical economic crop with high nutritional value, widely and globally cultivated. At present, avocado cultivation in China is mainly concentrated in Guangdong, Guangxi, Yunnan and other provinces, but the main cultivars are single (mostly Hass), and the cultivation performance varies in different producing areas. The development of the avocado industry is in urgent need of excellent cultivars suitable for local conditions. Thus, domestic scientific research institutions have strengthened avocado breeding, and a number of local-adapted cultivars have been selected. Tenglong, a new avocado cultivar with high yield, stable production and good quality, was bred by Guangxi South Subtropical Agricultural Science Research Institute, which performed excellently in regional trials of avocado producing areas in Guangxi. As early as 1956, Guangxi South Subtropical Agricultural Science Research Institute introduced a batch of Guatemalan race avocado seedlings for trial planting in its research base. After years of observation on the propagation and cultivation of these seedlings through multiple generations, the Tenglong strain was initially screened from the offspring of multi- generational propagated seedlings in 1986. In 2016, the grafted seedlings of Tenglong were planted in the avocado orchard of the institute with a spacing of 5 m×6 m (22 plants per mu), using 5- plant plots with 5 replicates. Through 3 generations of continuous observation on the growth and fruiting habits of the grafted seedlings, Tenglong showed stable economic traits, high-yield perfor-mance and good fruit quality. Its genetic independence was confirmed by Simple Sequence Repeat (SSR) molecular marker analysis. In 2019, yield measurement was conducted, and the single-plant yield ranged from 22 kg to 38 kg. In 2020, field identification was carried out, with an average single-plant yield of 22.8 kg. In February 2022, an application for new plant variety rights was filed with the name Tenglong. In December 2024, it passed the certification of improved forest tree varieties by the Forest and Grass Variety Certification Committee of Guangxi Zhuang Autonomous Region, with the certification number Guir-SC-PA-022-2024. Tenglong is a mid-maturing avocado cultivar for fresh consumption. It has vigorous tree vigor, a tall tree shape and luxuriant branches and leaves. The leaves are elliptical, with a length to width ratio of 2.5 and a shape factor of 0.528 0. It has type A flowers, and the flowering period is in early March. The fruit development period is 162-172 days, which ensures sufficient nutrient accumulation. The fruits ripen in early September; when ripe, the fruit stalks become yellow and the peel is smooth and green. Grafted seedlings can bloom and bear fruit in the 3rd year after planting, and enter the full fruiting period in the 4th-5th year, with a yield of about 501.6 kg per 666.7 m² during the full fruiting period. The fruits of Tenglong are elliptical, with a fruit shape index of 1.44. The average single fruit weight at maturity is 511.9 g, the peel thickness is 0.81 mm, and the edible rate is 78.6%. The soluble solid content is 5.6%, the dry matter content is 19.39%, the protein content is 0.84 g·100 g-1 , the vitamin C content is 9.23 mg·100 g-1 , the total sugar content is 1.54 g·100 g-1 , and the fat content is 14.6 g·100 g-1 . The peel of fresh fruits is medium olive green and smooth, while that of ripe fruits turns yellowish- green. The flesh is delicate and soft. Compared with the control cultivar Guikenda 2, Tenglong has larger fruits, higher edible rate, significantly lower astringency (not obvious in avocado), better taste, more stable yield and better commercial quality. Tenglong has strong adaptability and is easy to cultivate and manage. It is suitable for cultivation in areas with an annual average temperature of 21- 23 ℃, a minimum temperature of ≥13.5 ℃ in the coldest month, an extreme low temperature of ≥0 ℃, an annual rainfall of 1000-2000 mm and little typhoon impact. The suitable soil is sandy loam with a depth of more than 1.0 m, a groundwater level below 1.5 m and a pH value of 4.5-6.0. Due to its excellent economic traits, early fruiting, as well as high and stable yield, Tenglong is suitable for promotion and cultivation in Chongzuo area of Guangxi and other ecological areas with similar conditions.