Studies On Comparison Of Cold-Resistance In Different Culitivars Citrus Fruits

Low temperature is an important factor that limits plant growth and distribution. Citrus is subtropical plants, and suffers low temperature damage frequectly. China, original homeland of citrus, owns most citrus germplasm in the world and can selects cold-resistant varieties to be cultivated. But systemic examination of citrus cold resistance had not been reported up to date. To realize the cold-resistance of most varieties in China, we tested most of citrus germplasm planted in the National Citrus germplasm (Chongqing) and Huazhong Agricultural University (Wuhan) by the method of electronic leakage.The main results are as follows:1. The average of semilethal temperature of mandarin is -7.83℃. Among 28 Mandarin varieties testd, Owari wase is the most chilling-resistance (-10.9℃), Xiangci No. 43 is the weakest one (-3.7℃). As a whole, the cold-resistance of mandarins planted in Huazhong Agricultural University is slightly weak than that planted in Chongqing.2. The average of semilethal temperature of tangerine is -8.52℃. Among 40 Tangerine varieties tested, Wanmi No.3 is the most chilling-resistance(-12℃). the cold-resistance of tangerines planted in Huazhong Agricultural University is basically the same with that planted in Chongqing.3. Among 38 Hybird varieties tested. The average of semilethal temperature of tangerine is -9.54℃. It is the most chilling-resistance except Trifoliate Orange, Murcott is the weakest one (-5.5℃). As a whole, the cold-resistance of tangerines planted in Huazhong Agricultural University is slightly strong than that planted in Chongqing.4. The average of semilethal temperature of orange is -8.6℃. Among 45 Orange varieties tested, the cold-resistance of Cutter Valencia orange and Jincheng is weaker than the other Orange cultivars. As a whole, the cold-resistance of oranges planted in Huazhong Agricultural University is slightly strong than that planted in Chongqing.5. The average of semilethal temperature of pummelo is -6.26℃. Among 34 Pummelo varieties tested, Shatianyou is the weakest chilling-resistance(-4.3℃). As a whole, the cold-resistance of pummelos planted in Huazhong Agricultural University is slightly weak than that planted in Chongqing.6. Among 5 Lemon varieties tested, the cold-resistance of them is weak.(-5.68℃), the cold-resistance of Eureka Lemon planted in Huazhong Agricultural University is slightly strong than that planted in Chongqing. 7. The average of semilethal temperature of kumquat is -6.75℃. Among 6 Kumquat varieties tested, Changshou jingan is the most chilling-resistance(-8.9℃). As a whole, the cold-resistance of kumquats planted in Huazhong Agricultural University is basically the same with that planted in Chongqing.