Evaluation of the juice brix of wild sugarcanes (Saccharum spontaneum) indigenous to Japan

Modern sugarcane cultivars are derived from the interspecific crossing between Saccharum officinarum and wild sugarcane, Saccharum spontaneum. The introgression of valuable characteristics from wild sugarcane is recognized as extremely important, but this process typically requires long-term effort over multiple generations of backcrosses owing to the low sugar content of the initial interspecific hybrids. In this study, we aimed to identify Japanese wild sugarcanes with high juice brix in order to promote effective interspecific crossing of sugarcane. Sixty-four accessions from the Nansei Islands and 70 accessions from the Honshu were evaluated for juice brix. Wild sugarcanes with high juice brix were demonstrated to exist among wild sugarcanes indigenous to the Honshu. A significant difference was observed between the median juice brix values of wild sugarcanes of the Nansei Islands and those of the Honshu. The relationship between juice brix and stem traits was then examined in 20 wild sugarcanes, 10 each from the Nansei Islands and the Honshu. The reproducibility of juice brix value in both experiments was confirmed. In contrast to juice brix, stem traits, such as length, diameter, and volume, were typically smaller in wild sugarcanes from the Honshu. Moreover, a negative correlation was observed between the index of stem volume and juice brix. In this study, we identified outstanding wild sugarcanes with high juice brix. Using germplasms from the identified wild sugarcanes in interspecific crossing could contribute to the increases in both yield and sugar content.     

桂糖甘蔗新品系黑穗病抗性鉴定及结果分析

防治甘蔗黑穗病最有效的途径是种植抗病品种,而评价甘蔗抗黑穗病是抗病品种选育过程中重要程序。本研究对广西农科院甘蔗研究所选育的8个桂糖甘蔗新品系进行人工浸渍接种甘蔗鞭黑粉菌混合冬孢子悬浮液,同时调查大田自然发病情况,收集一新一宿黑穗病发病情况。 ROC22号为对照品种,综合评价桂糖甘蔗新品系对黑穗病的抗性。结果表明：抗性类型为抗病的品系有2个,分别为桂糖12-765和桂糖12-2262。抗性类型为中抗的品系有2个,分别为桂糖12-2476和桂糖12-2004。抗性类型为中感的品系有1个,为桂糖12-162。抗性类型为感病的品系有3个,分别为桂糖12-762、桂糖12-2425和桂糖12-917。对照品种ROC22的综合抗性类型为感病。对比人工接种和自然发病结果,人工接种黑穗病更准确评价甘蔗品种抗黑穗病的水平,为选育高产高糖高抗黑穗病甘蔗品种提供依据。     

与甘蔗抗黑穗病基因连锁的SSR标记筛选

黑穗病是世界各植蔗区最普遍、最主要的一种气传真菌性病害。为筛选与甘蔗抗黑穗病基因连锁的分子标记,利用高抗和感病亲本杂交的后代群体为材料,分别应用浸渍法和针刺法进行人工接种,通过一年新植一年宿根的抗病性鉴定,采用混合分组分析法（Bulked Segregant Analysis,BSA）构建了抗感池,并结合SSR（Simple Sequence Repeat）分子标记技术筛选出一个与甘蔗抗黑穗病性基因连锁的SSR标记,该标记在甘蔗抗黑穗病育种的辅助选择中具有应用潜力。     

Fibre digestion potential in sugarcane across the harvesting window

The objectives of this study were to determine the proportion of indigestible neutral detergent fibre (iNDF) in the neutral detergent fibre (NDF) fraction of sugarcane, to estimate changes in NDF digestibility (NDFD) during the harvesting window and to predict sugarcane digestibility based on its fibre fractions. Whole plants of the IAC86‐2480 and IAC93‐3046 varieties were collected during the harvesting windows in 2007 and 2009, respectively. The in vitro true dry matter digestibility (IVTDMD) and fibre contents (NDF, iNDF, acid detergent fibre) were determined by near infrared reflectance spectroscopy (NIRS). The NDFD and potentially digestible NDF digestibility (pdNDFD) were estimated, and the fractional digestion rate of pdNDF was calculated. There was no relationship between growing days and iNDF as a proportion of NDF (P = 0·28) or with the fractional digestion rate of pdNDF (P = 0·30). Therefore, NDFD (mean = 335 g kg^?1) and pdNDFD (mean = 657 g kg^?1) remained almost constant during the harvesting window (P = 0·70 and P = 0·32 respectively). Acid detergent fibre and NDF were the best predictors of sugarcane dry matter (DM) digestibility. In conclusion, NDFD seems to be unchanged during crop growth. The point at which to harvest sugarcane as a forage source should therefore be decided based on NDF concentration, which is greatly influenced by sucrose accumulation.     

美国引进甘蔗品种对黑穗病的抗性鉴定与初步评价

为筛选出抗甘蔗黑穗病的优异亲本材料,采用人工浸渍接种法对27个甘蔗品种进行1年新植试验的黑穗病抗性鉴定。通过潜育期(LP)、持续发病期(SDD)、累计丛发病率(IP)、累计茎发病率(IS)和病情进展曲线下的面积(AUDPC)这5个病情参数,结合标准对照种的抗性表现,综合评价参试品种的抗性,并采用系统聚类分析进行验证。结果表明:5个病情参数之间的相关性均达到极显著水平,是甘蔗黑穗病抗性鉴定与评价的重要指标。参试品种中,未发病品种6个,占22.22%;高抗(HR)品种5个,占18.52%;抗病(R)品种10个,占37.04%;中抗(MR)品种1个,占3.70%;中感(MS)品种2个,占7.41%;感病(S)品种3个,占11.11%。系统聚类分析的结果与参试甘蔗品种的抗性表现一致。     

玉米抗瘤黑粉病生理生化特性及基因表达分析

采用盆栽试验，以玉米高抗瘤黑粉病自交系齐319和高感自交系掖478为材料，采用注射法接种瘤黑粉菌，从生理生化及防御酶和相关抗病基因转录表达等方面，分析不同抗性玉米种质对瘤黑粉病的抗病特征。结果表明，接种后，2个自交系的苯丙氨酸解氨酶(PAL)、超氧化物歧化酶(SOD)和多酚氧化酶(PPO)活性增强，可溶性糖和脯氨酸(Pro)含量增加，而可溶性糖(SS)含量降低。利用RT-PCR对SOD、PAL、PR-l、PR-2a、COI1和LOX基因的相对表达量分析表明，接种瘤黑粉病菌后，不同抗性材料中抗病相关基因的转录水平均显著提高，抗病材料中的表达时间基本均早于感病材料，基因的转录水平均随着接种时间的增加而上升。在接菌后期，感病材料中防御酶基因和抗病相关基因的表达量大于抗病材料。     

室内人工接种玉米丝黑穗病抗性分级标准的建立

以40份已知抗性级别的玉米自交系为试材,采用优化的苗期室内接种技术接种丝黑穗病菌并检测,将侵染率与历年田间平均发病率进行回归分析,进而确定该评价方法的抗性分级标准,最终组装形成完整的评价技术体系。结果表明,苗期室内接种病菌后40份玉米自交系的侵染率与历年平均田间接种发病率之间存在极显著正相关,相关系数r=0.857 0,回归方程为y=0.000 4x~3-0.066 7x~2+3.813 7x+17.494。抗性分级标准:侵染率0~20.0%为高抗,20.1%~40.0%为抗病,40.1%~50.0%为中抗,50.1%~90.0%为感病,90.1%~100%为高感。     

高抗黑穗病甘蔗新品种‘中糖2号’的选育

本文详细阐述了高抗黑穗病、高产高糖的‘中糖2号’甘蔗新品种的选育过程,并就其蔗茎产量、抗黑穗病鉴定、特征特性等进行综合分析。‘中糖2号’（ZT2）是中国热带农业科学院热带生物技术研究所从‘热引1号’ב新台糖22号’（ROC22）杂交组合后代中选育出的甘蔗优良新品种,2019年获得农业农村部认定的非主要农作物新品种登记[编号：GPD甘蔗（2018）460029]。该品种表现为出芽整齐均匀、直立、易脱叶、抗倒伏、适宜机械化,高抗黑穗病。在海南临高的试验结果表明,‘中糖2号’1 a新植2 a宿根连续种植3 a平均蔗茎产量（117 080 kg/hm²）比对照‘新台糖22号’（96 330 kg/hm²）增产21.54%,其中宿根1 a和宿根2 a宿根甘蔗的蔗茎产量分别是112 875 kg/hm²和110 625 kg/hm²,分别比对照‘新台糖22号’增产27.82%和34.73%。‘中糖2号’1 a新植2 a宿根连续种植3 a单位面积平均含糖量（14 756 kg/hm²）比对照‘新台糖22号’增18.61%,其中宿根1 a和宿根2 a的宿根甘蔗的含糖量分别为14 516 kg/hm²和13 874 kg/hm²,分别比对照‘新台糖22号’增25.29%和29.17%。多年的黑穗病自然发病调查结果显示,‘中糖2号’对黑穗病表现为高抗,人工接种结果也表明其为高抗。‘中糖2号’为高抗黑穗病的高产高糖新品种,既为甘蔗育种提供抗病的亲本材料,也为甘蔗生产提供抗病的生产用种。     

Yield of sugarcane varieties and their sugar quality grown in different soil types and inoculated with a diazotrophic bacteria consortium

Sugarcane is a crop of great economic, social, and environmental relevance in Brazil. The country is the largest sugar producer and the second largest bioethanol producer in the world. The goal of this study was to evaluate the efficiency of a sugarcane inoculant composed of five diazotrophic bacterial strains, as well as nitrogen fertilization of two sugarcane varieties. Two experiments were carried out on two varieties using an experimental design composed of complete randomized blocks in a factorial of two varieties and three treatments with four replicates. The treatments can be described as: inoculation with the consortium of five diazotrophic strains, or N fertilization with 120 kg ha^?1, and one control treatment. The following parameters were then evaluated: stem yield, accumulation of total dry matter, nitrogen content, quality of the sugarcane juice, and ¹⁵N natural abundance on flag-leaves. Inoculation and N fertilization on the Sapucaia plantation promoted increases of stem yield equivalent to 22.3 and 26.5 Mg ha^?1 in the RB867515 variety, in comparison to the control, respectively. Inoculation and N fertilizer used for the Coruripe plantation increased stem yield of 38.0 and 42.4 Mg ha^?1, respectively, with the RB867515 variety, while RB72454 showed increases of 16.7 and 37.5 Mg ha^?1, both compared to the control. Biological nitrogen fixation was not affected by the treatments, however, both treatments increased the total recoverable sugar yield. Benefits from inoculation appeared to promote plant growth due to the plant–bacteria interaction.     

Methylotrophic yeast,lactic acid bacteria and glycerine as additives for sugarcane silage

The ensiling of sugarcane results in high dry‐matter (DM) loss, but the addition of glycerine may compensate for the loss during ensiling. Methanol is the most undesirable contaminant of crude glycerine destined for animal feeding. The aim of this study was to evaluate the ability of the yeast strain Pichia methanolica NCYC 1381 to reduce the methanol concentration in sugarcane silage inoculated with Lactobacillus hilgardii CCMA 0170 + glycerine. A randomized design consisted of four dose rates of glycerine (0, 4, 8 and 12% of fresh forage), three periods of silage fermentation (11, 34 and 68 d) and three combinations of microbial additives [L. hilgardii (LH), L. hilgardii plus P. methanolica (LH + PM) and without microbial additive (WI)]. The DM of the fresh sugarcane was 275 g kg^?1. The linear reduction in neutral detergent fibre caused by glycerine inclusion was probably due to a dilution effect. The LH treatment increased the concentrations of the succinic, acetic and propionic acids, and 1,2‐propanediol, and reduced the yeast population. The LH + PM treatment increased DM loss of sugarcane silage with 12% glycerine and L. hilgardii CCMA 0170 (6·1 log cfu g^?1 of FM) reduced the DM loss when compared to the silage without additives. Under the conditions of the experiment, the P. methanolica treatment did not reduce the methanol concentration in silage.     

Effects of Lactobacillus buchneri isolated from tropical maize silage on fermentation and aerobic stability of maize and sugarcane silages

This study was aimed to perform a screening of Lactobacillus buchneri strains from maize silage and use them as inoculant in maize and sugarcane silages. In all, 151 lactic acid bacteria (LAB) strains were isolated from whole‐plant maize silage, and their identification was based on the sequence analysis of 16S rDNA. In total, 15 strains were categorized to the L. buchneri group and eight of these were selected based on growth rate and fermentation pattern. The selected strains were evaluated on fermentation and aerobic stability of maize and sugarcane silages. For maize, the inoculated silages had lower pH and higher LAB population, but lower acetic acid concentration in comparison with the untreated control silage. For sugarcane silage, the strains 56.1, 56.4 and 40788 resulted in highest dry‐matter (DM) content and lowest DM losses. However, only the strain 40788 showed lowest counts of yeasts and moulds. Sugarcane silages inoculated with the strains 56.9, 56.26 and the untreated control silage showed highest concentrations of lactic acid and ethanol, besides the great DM losses. Even so, for both crops, the aerobic stability was not affected by inoculation. After air exposure, all silages increased temperature and had high population of yeast and moulds. Nevertheless, the strains 56.1 and 56.4 are promising for use as a silage inoculant.     

Evaluation of resistance to Sorghum mosaic virus (SrMV) in 49 new elite sugarcane varieties/clones in China

Mosaic disease is a systemic, seed-cane transmitted disease in sugarcane. Selective breeding and planting of resistant varieties is the most economical and effective measure for controlling this disease. In this study, resistance to Sorghum mosaic virus (SrMV-HH, GenBank accession number DQ530434), the predominant pathogen of mosaic disease in the Chinese cane-growing regions, was evaluated in 49 new elite sugarcane varieties/clones. Resistance ratings were determined as disease incidence after a stalk-cutting inoculation and RT-PCR detection in 2011 and 2012. Disease incidence under natural conditions was also used as a reference for resistance rating. The results demonstrated that of the 49 varieties/clones tested, 31 (63%) were scored between highly resistant (Grade 1) to moderately resistant (Grade 3). Of these, nine (18%; Yuegan 40, Yuegan 42, Yuetang 55, Yunzhe 03-194, Yunzhe 99-596, Yunrui 06-189, Guitang 30, Dezhe 03-83, and Mintang 01-77) were highly resistant (Grade 1), and seven (14%; Funong 0335, Liucheng 05-129, Yuetang 96-86, Yunzhe 01-1413, Yunzhe 03-258, Yunzhe 06-80, and Guitang 02-351) were resistant (Grade 2). These results may facilitate future efforts to breed varieties with further improved resistance to SrMV and may provide elite resistance resources and a reference for selecting and planting elite resistant varieties to control sugarcane mosaic disease effectively.     

Fibre digestibility and its relationships with chemical and morphological traits in thirty‐two sugarcane varieties

The objectives of this study were to determine the range of neutral detergent fibre (NDF) digestibility across sugarcane varieties and predict dry‐matter (DM) and NDF digestibility based on morphological and chemical composition. Whole plants of thirty‐two commercial varieties were collected after 12 months regrowth (second cut) and evaluated for morphological traits, chemical composition, in situ digestibility of NDF (NDFD) and of DM (DMD), in vitro NDFD (IVNDFD) and gas production dynamics from isolated NDF. The content of NDF ranged from 404 to 547 g kg^?1 DM, DMD was between 593 and 739 g kg^?1 and NDFD varied from 270 to 363 g kg^?1. Cluster and discriminant analyses for NDFD agglomerated sugarcane genotypes into three groups (high, medium and low NDFD). The contents of NDF and lignin were the best univariate predictors of sugarcane DMD and NDFD respectively. Therefore, associating NDF and lignin improved the accuracy of DMD prediction. Associating lignin concentration with the number of dry leaves and stalk length significantly improved the goodness of fit of NDFD prediction. Contrary to expectations, silicon concentration was not related to NDFD. The principal component analysis patterned the content of neutral detergent solubles, NDFD and variables related to DM yield in different components. Hence, these characteristics would coexist in the same variety. Based on Lucas test and kinetics of gas production from NDF, sugarcane potentially digestible NDF (pdNDF) can be considered almost uniform (pdNDF digestibility = 677 g kg^?1). In conclusion, associating chemical composition and morphological traits can successfully improve the screening of sugarcane genotypes for animal nutrition.     

Simulation of seasonal stalk water content and fresh weight yield of sugarcane

Stalk water content is an important variable for a sugarcane simulation model as sugar industries in many countries use cane yield and sucrose content on a wet mass basis for payment and yield reports. The prime objective was to develop a stalk water content module (SWCM) that can be incorporated into a sugarcane simulation model. SWCM starts from consideration of the dynamics of water concentration (ρ, g water g⁻¹ dry matter) along stalks and through seasons. The quantities of stalk water were modelled separately for the top and basal sections of the millable stalks. Field observations showed that the stalk water concentration (ρ) declined from 7.8 to 11.8 in the top internodes to 1.6–2.9 g water g⁻¹ dry matter in bottom internodes. In the basal section, ρ ranged from 1.98 in winter to 2.83 g water g⁻¹ stalk dry matter in summer. A two-parameter equation was used to model ρ and resulted in a range of coefficients of determination from 0.8 to 0.97 for six varieties. The SWCM was developed to simulate both the effects of seasonal variation and the age of internodes on the quantity of stalk water. The module was incorporated into a process oriented model of sugarcane growth for validation against field observations in tropical and subtropical areas of Australia and Hawaii, USA. Comparison of observed yields with cane yield simulated by the model that included the SWCM, gave an average of R² of 0.95, compared with the average of R² of 0.97 for simulation of stalk dry matter. The average relative root mean squared error (RMSE) was 15.2% in simulation of cane yield and 15.1% for simulation of cane dry weight. The module can be readily incorporated into a model that simulates sugarcane dry matter so that commercial crop yield can be estimated.     

甘蔗间作不同豆科作物对甘蔗植株内生细菌多样性的影响

解析甘蔗间作不同豆科作物对甘蔗植株内生细菌多样性的影响,旨在评价甘蔗间作不同豆科作物对甘蔗植株健康状况及抗性的作用效果。结果发现,与单作的甘蔗（CK）相比,甘蔗间作黄豆显著提高甘蔗内生细菌的多样性和丰富度;间作绿豆虽然有助于提升甘蔗植株内生细菌多样性与丰富度,但与CK之间无显著差异;间作花生导致甘蔗植株内生细菌多样性与丰富度显著降低。门分类水平,与CK相比,间作处理甘蔗植株中变形杆菌门（Proteobacteria）内生细菌丰度占比急剧下降,放线菌门（Actinobacteria）以及属于其他（others）分类的内生细菌丰度占比上升;属分类水平,与CK相比,间作处理甘蔗植株中泛菌属（Pantoea）和Burkholderia-Paraburkholderia属丰度占比下降,红球菌属（Rhodococcus）内生细菌丰度占比上升;另一方面,unclassified_f__Micrococcaceae和Pseudarthrobacter是间作甘蔗植株中特有的内生细菌优势属,但同时草螺菌属（Herbaspirillum）和Williamsia属内生细菌缺失。此外,Rubrobacter、norank_f__MSB-1E8、类诺卡氏菌属（Nocardioides）、norank_c__Actinobacteria、norank_f__Euzebyaceae、Gaiella、Defluviicoccus、norank_f__Elev-16S-1332、norank_o__Acidimicrobiales、norank_f__Propionibacteriaceae、norank_o__Gaiellales、norank_f__Gemmatimonadaceae是甘蔗/黄豆间作（A）处理中甘蔗植株特有的内生细菌优势属;链霉菌属（Streptomyces）、马赛菌属（Massilia）、分枝杆菌属（Mycobacterium）、甲基杆菌属（Methylobacterium）、Sinomonas、罗思河小杆菌属（Rhodanobacter）、金黄色杆菌属（Chryseobacterium）、根霉菌属（Rhizomicrobium）是甘蔗/绿豆间作（B）处理中甘蔗特有的内生细菌优势属。甘蔗/花生间作模式下,甘蔗植株根系中不存在特有的内生细菌优势属;而草螺菌属（Herbaspirillum）和Williamsia是甘蔗单作模式下甘蔗植株根系中特有的内生细菌优势属。甘蔗间作黄豆和绿豆不仅有助于提升甘蔗植株根系内生细菌的多样性与丰富度,而且改善了甘蔗植株根系内生细菌群落结构组成,尤其间作黄豆效果更佳;与之相反,甘蔗间作花生无助于提高甘蔗植株根系内生细菌的多样性与丰富度,亦不利于改善甘蔗植株根系内生细菌群落结构组成。     

Effect of chitosan on the preservation quality of sugarcane silage

We aimed to evaluate the effects of chitosan and microbial inoculant addition to sugarcane silage fermentation, gas and effluent losses, chemical composition, in situ dry matter (DM), neutral detergent fibre (NDF) degradation and aerobic stability. A completely randomized design with four treatments (n = 40) was performed. It was arranged in a 2 × 2 factorial scheme with chitosan [0 and 6 g/kg of sugarcane DM—1.66 g/kg of natural matter (NM)] and microbial inoculant (0 and 8 mg/kg on NM). Each g of inoculant contained 3.9 × 10¹⁰ UFC/g of Pediococcus acidilactici and 3.75 × 10¹⁰ UFC/g of Propionibacterium acidicipropionici. The addition of microbial inoculant increased lactic acid concentration in silos treated with chitosan. Furthermore, chitosan increased pH and tended to increase acetic acid of silage. In contrast, the inoculant decreased pH and acetic acid, besides increasing ethanol concentration. As chitosan addition increased DM recovery, inoculant addition decreased it. Chitosan decreased NDF and acid detergent fibre (ADF) level and increased DM degradation, while inoculant decreased DM content, DM and NDF degradation. In addition, chitosan improved the aerobic stability only in non‐inoculated silos. Thus, chitosan has a positive effect on silage fermentation, reducing fermentative losses, and improving silage chemical composition and degradation. Conversely, the addition of microbial inoculant negatively affected silage DM recovery, chemical composition, and its association with chitosan decreased the aerobic stability when compared to the exclusive use of chitosan.     

PCR detection of ratoon stunting disease pathogen and natural resistance analysis in sugarcane core germplasms

Exploring and utilizing resistant germplasm resources plays a pivotal role in breeding for disease resistance, while screening resistant germplasm is important for selecting and breeding varieties resistant to disease. In the present study, we used PCR to detect the ratoon stunting disease (RSD) bacterium Leifsonia xyli subsp. xyli (Lxx) in 137 sugarcane core germplasms from the National Nursery of Sugarcane Germplasm Resources (NNSGR, Kaiyuan, China) in 2009, 2010 and 2011. A total of 21 germplasms that tested negative for Lxx in 2009 and 2010 were selected for further Lxx detection after being subjected to artificial inoculation in 2011 and 2012. The 21 core germplasms that were negative for Lxx after natural infection and artificial inoculation can provide elite resistance source materials and reference frames for the effective breeding of RSD-resistant sugarcane varieties. Under natural conditions, 116 (84.67%) and 21 (15.33%) out of 137 germplasms were positive and negative for Lxx, respectively, as determined by PCR detection, which suggests that a relatively high ratio of sugarcane core germplasms was sensitive to RSD, while few were resistant to RSD. The sequencing and analysis of 30 randomly selected PCR products showed that all 30 sequences were identical or highly homologous to the corresponding Lxx genome region published in GenBank (99.54–100% similarity). Lxx can be detected effectively and precisely by PCR. We therefore recommend PCR as a rapid, low cost and simple procedure to score sugarcane core germplasms for RSD resistance.     

取食番茄、辣椒和人工饲料对斜纹夜蛾生长发育和繁殖力的影响

分别用番茄果实、辣椒果实和人工饲料饲养斜纹夜蛾,观察不同食料对斜纹夜蛾(Spodoptera litura Fabricius)的生长发育、存活、不同龄期幼虫的粪便重量、成虫产卵量的影响,组建相应食料下的斜纹夜蛾实验种群生命表.结果表明:喂饲辣椒果实的斜纹夜蛾幼虫发育历期和全世代显著长于喂饲番茄和人工饲料,喂饲人工饲料的斜纹夜蛾不同龄期幼虫的粪便重量显著重于喂饲辣椒果实;种群趋势指数(Ⅰ)均大于1, 内禀增长力(rm)均大于0,斜纹夜蛾种群呈增长趋势.     

Nitrogen use efficiency and drought tolerant ability of various sugarcane varieties under drought stress at early growth stage

ABSTRACT

The experiment was conducted under glasshouse conditions to evaluate nitrogen use efficiency and drought tolerant ability of the five different sugarcane varieties (including NiF3, Ni9, Ni17, Ni21 and Ni22) under early growth stage from 60 to 120 days after transplanting. The results showed drought stress reduced the photosynthetic rate, growth parameters including plant height, leaf area; partial and total dry weights; and nitrogen use efficiency (NUE) traits including photosynthetic NUE, nitrogen utilization efficiency and biomass NUE of measured sugarcane varieties. The significant differences were found among varieties in growth parameters, dry weights, NUE traits and drought tolerant index (DTI). The significant positive correlations among NUE traits and DTI suggested higher NUEs could support better a tolerant ability to drought stress at the early growth stage. Because of larger contributions, DTIs for aboveground and stalk dry weight could be used as the important DTIs to evaluate drought tolerant ability in sugarcane varieties.     

Effect of Stubble Shaving after High-Level Cutting on the Growth and Yield of Forage Sugarcane,KRFo93-1, under Multiple Ratooning Cultivation

Abstract

In the production of sugarcane, stubble shaving that cuts the residual stubble of the previous crop is carried out to promote ratoon crop growth. On the other hand, in the production of feed crops, it is generally considered that high-level cutting increases the yield of the regrowth crop. In this study, the growth and yield of the forage sugarcane subjected to high-level cutting without stubble shaving (HC) were compared with those of the plants subjected to stubble shaving (Control) to clarify the necessity of stubble shaving in the cultivation of a forage sugarcane variety, KRFo93-1. The influence of high-level cutting on the growth and yield of ratoon crop was evaluated from the first ratoon crop (RC1) to sixth ratoon crop (RC6). Tiller number in the Control plot was not different from that in the HC plots in all ratoon crops from RC1 to RC6. Stem length was significantly larger in HC than in the Control plot in all ratoon crops at the initial stage of regrowth, and in RC1, RC3, RC5 and RC6 around the harvest time. Dry matter yield was significantly higher in HC than in the Control plot in RC1, RC3, RC5, RC6 and in the sum of the ratoon crops. Although no significant difference was observed in RC2 or RC4, the dry matter yield of HC exceeded that of Control plot. The increase in the dry matter yield of HC was due to an enhancement of stem growth, since the single stem dry weight were larger in HC than in Control plot. Thus, cultivation management without stubble shaving is recommended in KRFo93-1.