Abstract GT42 was observed in representative sugarcane fields in Jinguang Farm at multiple sites for many years， so as to provide reference for its extension. The results showed that GT42 performed well in Jinguang Farm. Its sucrose content was slightly higher than ROC22； and the yield of new plant was equivalent to ROC22， and the yield of ratoon and average yield of new plant and ratoon were much higher than the CK， exhibiting remarkably yieldincreasing superiority， especially under high fertility. GT42 has high yield， high sugar， strong ratoon property， strong disease resistance and good comprehensive traits， and is suitable for plantation in Jinguang Farm and sugarcane areas of the same type.
　　Key words Sugarcane； GT42； Jinguang farm； Performance
　　Received： October 23， 2017 Accepted： January 16， 2018
　　Jinfan WEI （1982-）， male， P. R. China， agronomist， devoted to research about breeding and extension of new sugarcane varieties.
　　*Corresponding author. Email： dyxj_32@163.com
　　Cane sugar industry is a conventional pillar industry in Guangxi. The planting area of sugarcane， cane production and sugar production in Guangxi rank the first in China， and Guangxi Province is thus the largest sugar production base in China. Sugarcane variety is the core of cane sugar production， and always attracts attention in various cane sugar production countries， and the innovation of new varieties is the precondition for the stable development of cane sugar industry[1]. The introduction of new sugarcane variety is one of the important ways to obtain good sugarcane variety， improve sugarcane yield and improve variety structure in various sugarcanegrowing area[2-5]， while the key here is whether the introduced variety could adapt to local natural condition and farming level[6]. Though sugarcane has stronger adaptability to various types of soil， differences in fertility would cause great differences in yield of sugarcane. Therefore， various sugarcane varieties differ in most suitable planting area. Furthermore， differences in climate between different years also greatly affect yield of sugarcane. In the sugarcane areas of Guangxi Province， the local major sugarcane variety is ROC22， which is suffering from idioplasmatic degeneration， poor ratoon property and low yield of ratoon cane， and it is urgent to develop more better new sugarcane varieties. Guitang 42 （GT42） is a new sugarcane variety bred in 2013 with good comprehensive traits. In this study， GT42 was planted in representative soil at different fertility levels selected in Jinguang Farm， and its performance in multiple years were observed and evaluated， so as to provide reference for the extension of GT42 in Jinguang Farm and sugarcane areas of the same type. 　　Materials and Methods
　　Experimental materials
　　The tested varieties was GT42， which was bred by Sugarcane Research Institute， Guangxi Academy of Agricultural Sciences， with local dominant variety ROC22 as control （CK）. The tested soil was the dryland with red soil at different fertility levels in Guangxi National Jinguang Farm. The previous crop was sugarcane， and nutrient contents of the experimental fields were detected， as shown in Table 1.
　　Experimental methods
　　In 2013-2016， after the determination of soil nutrient contents， three pieces of representative land were selected in the farm every year， and were divided into three groups， i.e.， the high， medium and low fertility groups， according to fertility level （Table 2）. Each piece of land had an area of 0.33-0.40 hm2， and each group was designed with three replicates. After the new plant experiment， ratoon was reserved. The seeding rate for the new plant experiment was 114 000 buds/hm2； fertilization was performed according to conventional dosages， i.e.， compound fertilizer （N∶P2O5∶K2O=13∶9∶7， produced by the farm） 2 250 kg/hm2， urea 25 kg/hm2， 18% calciummagnesium phosphate fertilizer 100 kg/hm2， and potassium chloride 30 kg/hm2； and other field management was according to conventional methods. Sucrose content was determined in the middle of each month from November to February of the next year， and the actual yield was determined during harvesting.
　　Results and Analysis
　　Agronomic traits and resistance performance
　　It could be seen from Table 3 that for new plant， the germination rate of GT42 was higher than ROC22 as the CK under high fertility， and lower than the CK under medium and low fertility， but the differences were all not significant. Under high and medium fertility， there were more effective seedlings and effective stems than the CK， with significant differences， while under low fertility treatment， GT42 had effective seedlings and effective stems less than the CK， with nonsignificant differences. The plant height of GT42 was lower than that of the CK under different fertility， and there were significance differences under medium and low fertility. Under all the fertility conditions， GT42 had smaller stem diameter than the CK， without significant differences. As to disease resistance， except dead heat rate under low fertility， the dead hear rate and smut rate of GT42 were both higher that the CK， without significant differences. It was indicated that new plant of GT42 had the germination rate equivalent to the CK， but more effective seedlings and effective stems than the CK. Overall， it grew better under high fertility， which was reflected by high germination rate， more effective stems and high plants. 　　Table 1 Nutrient contents in experimental fieldsg/kg
　　YearpHOrganic matterTotal nitrogenAvailable phosphorousAvailable potassium
　　20135.836.22.625.1319.6
　　5.123.81.017.4233.4
　　5.515.40.77.7127.1
　　20146.129.82.028.8294.6
　　5.626.41.315.7287.3
　　5.211.80.811.4103.7
　　20155.533.91.631.6337.1
　　4.920.81.418.3202.5
　　5.514.30.68.8131.7
　　20165.633.82.228.1278.4
　　5.321.41.214.5198.3
　　5.213.10.46.397.2
　　Table 2 Reference values for division of fertility levelg/kg
　　FertilizerOrganic matterTotal nitrogenAvailable phosphorusRapidly available potassium
　　High30-401.5-2.520-30 200-300
　　Middle20-301.0-1.510-20 100-200
　　Low10-200.5-1.05-10 50-100
　　As to ratoon cane， the ratooning rate of GT42 was 74.40%-112.40%； the effective seedlings and effective stems were more than the CK， and except the effective seedlings of ratoon 1 under lower fertility， there were significant or very significant differences. Except ratoon 2 and ratoon 3 under low fertility， the plant height of GT42 was higher than that of the CK， but only the difference of ratoon 3 under high fertility was significant. The cane diameter of ratoon 1 of GT42 was smaller or equivalent to that of the CK， without a significant difference， the values of ratoon 2 and ratoon 3 were larger or equivalent to those of the CK， and the differences were significant for ratoon 2 and ratoon 3. In the aspect of disease resistance， except that the dead heart rate of ratoon 2 was lower than the CK under high fertility， with a significant difference， GT42 showed the dead heart rate equivalent to the CK， without significant differences； and the smut rate of GT42 was smaller than that of the CK under all conditions， and except ratoon 1 and ratoon 3 under high fertility and ratoon 3 under low fertility， the differences were all significant. It was indicated that GT42 had good ratoon property which was reflected by more effective stems， and was thus advantageous compared with the CK， and its performance was better under high and medium fertility than under low fertility； and its ratoon cane had stronger smut resistance than the CK.
　　Table 3 Agronomic traits and resistance performance of GT42 under different fertility conditions
　　FertilityPlant stageVarietyGermination rate orsprouting rate∥%Effective seedlings103 seedlings/hm2Plant heightcmStemdiameter∥cmEffective stem103 seedlings/hm2Dead heartrate∥%Smut rate% 　　HighNew plantGT4268.00±3.88126.7±5.2*318.7±7.32.59±0.0573.2±1.6**7.48±0.790.33±0.23
　　ROC2266.78±2.21112.3±3.3326.5±3.42.62±0.0663.4±0.86.09±1.030.27±0.14
　　Ratoon 1GT4296.70±3.3095.5±2.7*323.1±18.12.60±0.0762.4±2.4**5.77±0.5813.90±4.28
　　ROC2287.50±2.3784.9±3.3308.3±6.82.69±0.6651.6±1.09.37±1.7920.13±6.36
　　Ratoon 2GT4279.05±1.5596.6±8.5*314.5±4.02.75±0.0662.2±1.2**2.45±0.95*10.65±2.65*
　　ROC2283.30±3.1077.6±5.2313.5±2.92.60±0.1445.2±0.75.80±1.9020.45±1.36
　　Ratoon 3GT42112.40±21.8291.3±6.4*315.9±7.1*2.66±0.2448.5±0.8**6.20±1.6716.00±1.54
　　ROC2282.50±10.2675.8±5.8289.0±5.62.51±0.1337.1±0.74.57±1.3518.70±3.28
　　MediumNew plantGT4260.23±2.28114.9±6.0299.6±8.3**2.66±0.0268.5±0.7*9.18±1.560.41±0.23
　　ROC2260.28±1.07109.6±5.2333.5±3.52.70±0.0465.6±1.07.75±1.020.33±0.18
　　Ratoon 1GT4292.67±5.0291.2±4.9*312.7±7.92.64±0.0566.2±0.29**8.50±1.978.00±1.87*
　　ROC2285.77±2.9581.3±1.7308.3±4.62.68±0.0752.2±2.216.31±0.9517.93±2.47
　　（Continued）
　　（Table 3）
　　FertilityPlant stageVarietyGermination rate orsprouting rate∥%Effective seedlings103 seedlings/hm2Plant heightcmStemdiameter∥cmEffective stem103 seedlings/hm2Dead heartrate∥%Smut rate%
　　Ratoon 2GT4279.55±1.7586.2±2.9*332.3±12.22.82±0.01*57.7±2.4*6.95±4.7511.40±1.32*
　　ROC2280.35±5.7273.2±2.7316.5±5.52.50±0.0443.3±0.75.75±4.3514.30±1.08
　　Ratoon 3GT4282.20±7.8978.7±3.1*313.3±10.32.71±0.04*57.4±1.6**7.40±2.3610.50±2.01*
　　ROC2296.20±9.3266.4±2.3299.0±7.82.56±0.0439.8±1.97.75±2.4122.80±5.23
　　LowNew plantGT4257.33±2.12106.9±4.8288.9±7.7*2.58±0.0364.9±1.95.95±1.530.30±0.12
　　ROC2259.33±2.27108.6±3.6313.8±1.92.59±0.0565.8±2.77.77±1.810.25±0.10
　　Ratoon 1GT4285.20±5.2791.4±8.4302.4±8.92.70±0.0559.3±2.7*8.40±2.059.90±1.42*
　　ROC2276.97±2.6081.9±3.5291.0±3.52.58±0.0446.7±4.29.41±1.9718.03±4.09
　　Ratoon 2GT4274.40±6.9086.1±4.23*289.5±9.72.73±0.0857.7±3.2**9.45±3.118.40±2.20*
　　ROC2288.80±7.7073.9±2.12298.5±5.52.55±0.0541.3±1.47.86±2.3418.30±3.81
　　Ratoon 3GT4276.20±6.2476.8±2.01*282.8±6.52.61±0.0457.4±3.4**9.40±2.1412.70±2.03
　　ROC2285.80±7.2867.7±1.23290.0±6.82.63±0.0436.2±2.28.42±2.0313.83±2.11
　　* and ** indicate a difference at significant （P<0.05） or very significant （P<0.01） level. Similarly hereinafter.
　　Yield performance
　　It could be seen from Table 4 that for new plant， the cane yield and sugar yield of GT42 were not significantly different from the CK under high and low fertility， but significantly higher than the CK under medium fertility. For ratoon cane， the cane yield and sugar yield of GT42 were higher than those of the CK， with significant or very significant differences. Though for the mean of new plant and ratoon 1， the cane yield and sugar yield of GT42 were only significantly higher than the CK under high fertility， for the mean value of new plant and ratoon 1 and 2 and the mean value of new plant and ratoon 1， 2 and 3， the average cane yield and sugar yield of GT42 were both significantly or very significantly higher than those of the CK， i.e.， with the ratoon years growing， the yield increase between GT42 and the CK increased， exhibiting remarkable superiority， and especially under high fertility， the yield increase was the highest. It was indicated that the yield of GT42 was equivalent to that of the CK for new plant， but higher than that of the CK for ratoon cane， and thus had remarkable superiority， which might be due to that it had more ratoon plants and a higher effective stem rate than ROC22， and the effective stems of ratoon 3 still could reach 48 500-57 400 plants/hm2. 　　Agricultural Biotechnology2018
　　Table 4 Yield performance of GT42 under different fertility
　　FertilityItemVarietyNew plantt/hm2Ratoon 1t/hm2Ratoon 2t/hm2Ratoon 3t/hm2
　　Mean of new plantand ratoon 1
　　t/hm2±CK
　　Mean of new plant andratoon 1 and 2
　　t/hm2±CK
　　Mean of new plant andratoon 1， 2 and 3
　　t/hm2±CK
　　High YieldGT42108.49±5.8894.86±6.31*102.81±7.29**75.20±4.23**102.65±5.23*14.76102.69±4.17**21.7799.94±4.64**24.10
　　ROC2296.90±3.6379.53±5.9166.43±7.0946.23±2.4289.45±4.59-84.33±5.01-80.53±5.89-
　　Sugar yieldGT4216.30±0.7914.92±1.06*15.65±0.95**11.38±0.94**15.71±0.70*15.4315.69±0.56**22.2915.26±0.66**24.47
　　ROC2214.59±0.5112.31±0.8410.09±1.067.17±0.7113.61±0.62-12.83±0.73-12.26±0.86-
　　MediumYieldGT4299.59±3.28*100.39±7.09*106.16±8.26**91.6±6.23**99.93±3.462.10102.32±2.80*14.66100.34±2.69**17.10
　　ROC22111.56±3.1679.61±2.3559.06±2.4853.64±2.1497.87±6.73-89.24±4.68-85.69±7.74
　　Sugar yieldGT4214.87±0.52*14.94±0.92*15.75±1.23**14.50±1.24**14.90±0.443.1115.09±0.37*12.1115.03±0.34*16.33
　　ROC2216.81±0.9912.00±0.238.99±0.648.00±0.8114.45±1.01-13.46±0.74-12.92±0.86-
　　LowYieldGT4285.58±4.4390.23±5.22*85.33±7.81*73.25±5.24**87.57±3.227.1787.08±2.80*14.8785.69±2.86*17.08
　　ROC2296.18±5.4662.42±7.4655.15±2.3549.66±2.1481.71±7.94-75.81±2.22-73.19±4.97-
　　Sugar yieldGT4212.73±0.6513.67±0.94*13.47±1.01*11.08±0.97**13.13±0.538.5113.20±0.44*17.0212.99±0.45*19.07
　　ROC2214.10±1.499.44±1.148.42±0.717.60±0.8112.10±1.11-11.28±0.51-10.91±0.87-
　　Sucrose performance
　　It could be seen from Fig. 1 that the sucrose content of GT42 was higher or lower than that of ROC22 under different fertility and different plant stages， the differences were not significant. It was indicated that the sucrose content of GT42 was equivalent to that of ROC22. From the average value of sucrose content， overall， the sucrose content of GT42 was slightly higher than that of the CK.
　　Discussion and Conclusions
　　Sugarcane is an important sugar crop and bioenergy crop. Ratoon sugarcane not only could save planting cost and prolong growth period， but also could bring forward earlymaturing time and improve sucrose content. Not only seed cane could be saved， but also the expanding propagation of good new varieties and the extension conducted by sugar enterprises could be facilitated[7-9]. Ratoon sugarcane is of great significance in production， and main sucroseproducing countries all pay much attention to the breeding and extension of sugarcane varieties with good ratoon property[7，10]. In the sugarcane area of Jinguang Farm， compared with ROC22， GT42 had a high yield increase， strong ratoon property and long ratoon years， exhibiting remarkable superiority. 　　Fig. 1 Sucrose performance of GT42 under different fertility conditions
　　Overall， GT42 performed well in Jinguang Farm. Its sucrose content was slightly higher than ROC22； and the yield of new plant was equivalent to ROC22， and the yield of ratoon and average yield of new plant and ratoon were much higher than the CK， exhibiting remarkably yieldincreasing superiority. GT42 has strong ratoon property， and is suitable for plantation in Jinguang Farm， especially under high fertility. It is advised to properly improve the rate of fertilizer application in fields with medium and lower fertility. The data of this research were the results obtained from many years of tests at multiple sites after statistical analysis， and have certain references value for GT42 in Jinguang Farm and sugarcane areas of the same type.
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