The resistance of grape germplasm resources to late frost damage

Abstract: 【Objective】Late frost is a natural disaster leading to extensive crop losses for fruit producersin the world. Although grapevine (Vitis vinifera L.) has a wide environmental adaptability, the late frostis a serious threat to grape production in frost-prone viticultural regions. Selection of grape cultivarswith strong resistance is a reliable method for avoiding late frost damage. The objective of this studywas to understand the resistance of different grape germplasm resources to late frost and to provide areference for breeding resistant variety and rootstock.【Methods】A severe late frost occurred on 6 and 7 April, 2018, causing damage to young shoots and swollen buds of grapevine in a large area of North-west China. During the cold wave, the daily minimum temperature fell to 0 degrees C in Yangling dis-trict of Shaanxi province which is located in the western part of Guanzhong plain. The occurance of thelate frost provided an opportunity for us to evaluate the resistant performance of grape germplasm re-sources to late frost. The field natural identification was employed to evaluate the resistance of grapegermplasm resources to late frost injury. The third day after late frost (9 April) , we carried out a identifi-cation of the late frost-resistance for 81 grape germplasm resources under field natural condition, includ-ing 56 accessions of 17 Chinese wild Vitis species or varieties and 8 accessions of 6 American wild Vitisspecies as well as 17 cultivars. All plants are above 5 years-old and are grown in the grape repository ofNorthwest A & F University, Yangling, Shaanxi, China. Three plants of each grape var. or acc. were in-vestigated. According to the proportion of damaged tender shoots and swollen buds to total germinatedbuds, the injury severity of each vine was recorded, and then the average injury severity of three vinesof the same var. or acc. was calculated. Finally, according to the average injury severity of each grapevar. or acc., the resistant level of the tested grape germplasm resources to late frost damage was dividedinto four classes: high resistance, resistance, susceptibility and high susceptibility.【Results】As a resultof late frost damage, lots of tender shoots of some grapevines showed varying degrees of water stain, wilting, browning and even blackness, but other grapevines had no changes or no sprouting, implyingthat the different grape germplasm resources had different resistance performance to the late frost.Among the Chinese wild Vitis species, V. quinquangularis, V. ficifolia, V. davidii var. cyanocarpa, and V.pseudoreticulata were frost-avoiding; V. yenshanensis, V. hancockii, and V. bashanica showed high resis-tance; V. thunbergii was highly resistant or resistant; V. shenxiensis, V. liubaensis, and V. hancockii wereresistant; There were resistance variation in intraspecies of V. amurensis, V. romanetii, V. piasezkii, V. davidii, and V. qinlingensis, in which the phenotypes wree from highly resistant to highly susceptible; V.davidii var. ningqiangensis was highly susceptible. For the American wild Vitis species, V. berlandieriwas frost-avoiding; V. labrusca and V. cinerea were highly resistant; V. riparia, V. orizonica and V. rupestris showed resistance. For the V. vinifera cvs., 'Thompson Seedless' had high resistance;'Zaomei-gui', 'Zaojinxiang', and'Cardinal'presented resistance;'Monukka''Xinyu'and'Jingxiu'showedsusceptibility. For the Euro-America hybrids, 'Kyoho'was highly resistant, 'Fujiminori''Wase Taka-sumi''Jingyou''Jupiter'and'Neptune'were resistant. For the hybrids of V. vinifera ×V. amrensis, 00-1-10 was frost-avoiding, 00-1-5 was highly resistant, 'Beichun'and'Zuoyouhong'were susceptible.【Conclusion】The resistance of Chinese wild Vitis and cultivars to late frost was complex. There werenot only highly resistant and resistant types, but also susceptible and highly susceptible types, while theAmerican wild Vitis species were highly resistant or resistant types. Among of them, V. quinquangula-ris, V. ficifolia, V. davidii var. cyanocarpa, V. pseudoreticulata, Vitis amurensis acc. Zuoshan-1, V. yen-shanensis, V. bashanica, V. baihensis, V. thunbergii, V. romanetii acc. Meixian-6, V. piasezkii acc. Guan-su-91, Liuba-8 and Liuba-6, V. davidii acc. Tangwei and Xuefeng, V. berlandieri, V. labrusca, V. cinereaas well as cultivars (or acc.) 'Thompson Seedless', 'Kyoho', 00-1-10, 00-1-5 were the important resis-tant germplasm resources to late frost damage. The resistance of grape germplasm resources to late frostwas not completely consistent with the tolerance to winter cold.