不同木薯品种(系)农艺性状分析及高产品种(系)筛选
Analysis of Agronomic Characteristics of Different Cassava Varieties (Lines) and Screening of High-Yielding Varieties (Lines)
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收稿日期: 2021-05-11 修回日期: 2021-07-3 网络出版日期: 2022-04-07
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Received: 2021-05-11 Revised: 2021-07-3 Online: 2022-04-07
作者简介 About authors
肖明昆,研究方向为热带作物栽培与资源开发利用,E-mail:
为了解影响木薯产量的主要因素,筛选高产木薯品种(系),通过主成分分析对10个品种(系)的9个主要农艺性状指标进行量化对比分析。结果表明,10个木薯品种(系)的农艺性状除落叶高度和块根粗无显著差异外(P>0.05),其余农艺性状间均具有显著差异(P<0.05),品种(系)SC9、SC124和58-7的农艺性状变异较大,农艺性状中又以单株产量、地上鲜重、鲜薯个数和主茎粗的变异系数最大。鲜薯个数、块根长和块根粗是影响单株产量的关键因子。通过主成分分析提取了2个主成分,累积方差贡献率达88.1%,反映了农艺性状指标的基本信息,其中,鲜薯个数是第1主成分的主导变量,块根长是第2主成分的主导变量。10个木薯品种(系)中,SG-9的综合得分最高,GMT和SC9的产量优势明显,可作为种植推广的品种。
关键词:
In order to explore the main factors affecting the yield of cassava, and screen high-yielding cassava varieties (lines), nine main agronomic traits of ten cassava varieties (lines) were compared and analyzed by using principal component analysis. The results showed that the agronomic traits of ten cassava varieties (lines) had significant differences (P < 0.05) except deciduous height and root thick (P > 0.05). The agronomic traits of SC9, SC124 and 58-7 had great variation. Among agronomic traits, the variation coefficients of yield per plant, aboveground fresh weight, number of fresh tubers and stem diameter were the largest. The number of fresh tubers, root length and thick were the key influencing factors of yield per plant. Two principal components were extracted by principal component analysis, and the cumulative variance contribution rate reached 88.1%, which reflected the basic information of agronomic traits. Among them, the number of fresh tubers was the dominant variable of the first principal component, and root length was the dominant variable of the second principal component. Among the ten cassava varieties (lines), SG-9 had the highest comprehensive score, GMT and SC9 had obvious yield advantages and could be used as planting and extension varieties.
Keywords:
本文引用格式
肖明昆, 刘光华, 宋记明, 刘倩, 段春芳, 姜太玲, 张林辉, 严炜, 沈绍斌, 周迎春, 熊贤坤, 罗鑫, 白丽娜, 李月仙.
Xiao Mingkun, Liu Guanghua, Song Jiming, Liu Qian, Duan Chunfang, Jiang Tailing, Zhang Linhui, Yan Wei, Shen Shaobin, Zhou Yingchun, Xiong Xiankun, Luo Xin, Bai Lina, Li Yuexian.
木薯(Manihot esculenta Crantz)为大戟科木薯属植物,是世界三大薯类作物之一,也是全球第六大粮食作物[1],主要种植于非洲、亚洲和拉丁美洲的热带和亚热带地区[2]。在一些非洲国家,每天约25%的能量摄入是由木薯提供[3]。19世纪20年代,为缓解粮食危机、保障粮食安全而引入中国,起初主要种植于广东、广西和海南,现在已逐步扩大到云南、福建、贵州、湖南和江西等省份[4]。云南省作为木薯种植的主要产区之一,不但具有毗邻越南、泰国等木薯主产国的区位优势,同时也具备土壤条件好、日照充足和适种区域较为广阔的自然优势条件,因此发展前景广阔[5]。但目前云南推广种植的木薯品种均从海南、广西等地引进,品种数量少[6]。经多年连作,现有品种产量下降,抗病虫害能力减退,品种退化严重。因此,筛选适宜本区域种植的高产优质木薯新品种(系)颇为重要。
1 材料与方法
1.1 试验材料及试验地区概况
以10个不同木薯品种(系)(表1)为试验材料。试验在云南省农业科学院热带亚热带经济作物研究所潞江坝基地(98°52′53″ E,24°58′52″ N)进行,海拔704m,属低纬度准热带季风雨林偏干热河谷过渡类型气候,年均气温21.5℃,年均降雨量755.3mm,年蒸发量2111.5mm,≥10℃活动积温7800℃,年日照时数2325.75h,相对湿度70%。土地相对平坦,水利条件优越,土壤为冲积母质发育的沙壤土,有机质1.3%、pH 6.6、全氮1.09g/kg、全磷0.038%、全钾2.5%、镉含量0.11mg/kg、汞含量<0.01mg/kg。
表1 试验材料及来源
Table 1
品种(系) Variety (line) | 来源 Source |
---|---|
277 | 中国热带农业科学院环境与植物保护研究所 |
43-3 | 中国热带农业科学院热带生物技术研究所 |
58-7 | 中国热带农业科学院热带生物技术研究所 |
GMT | 中国热带农业科学院热带生物技术研究所 |
GR891 | 广西壮族自治区亚热带作物研究所 |
SC-1 | 云南省农业科学院热带亚热带经济作物研究所 |
SC124 | 中国热带农业科学院热带作物品种资源研究所 |
SC205 | 中国热带农业科学院热带作物品种资源研究所 |
SC9 | 中国热带农业科学院热带作物品种资源研究所 |
SG-9 | 云南省农业科学院热带亚热带经济作物研究所 |
1.2 试验设计
2019年3月起垄种植,采用完全随机区组设计,设置10个处理,每个处理种植30株,重复3次。每个小区面积16m2,试验区两边各设置1垄保护行。半高垄双行栽培,垄高25cm,东西方向定植,行间距1.0m×0.8m。用40%啶虫脒可溶性粉剂1500倍和5.7%甲氨基阿维菌素苯甲酸盐水分散粒剂2000倍混合液浸泡木薯种茎10min后种植。在植株封行前,统一追施钾肥450kg/hm2,其他田间管理按常规栽培技术进行,各处理田间管理措施一致。
1.3 测定项目与方法
于2020年3月中旬采收,每个品种(系)随机从各小区选取10株进行调查,重复3次,共计300株。基于《引进农作物种质资源试种鉴定技术规程》(NY/T 1737-2009)[14]中种质资源植物学特性鉴定要求和方法,分别调查株高、主茎粗、第1分枝高、落叶高度、地上鲜重、鲜薯个数、块根长、块根粗和单株产量9个主要农艺性状指标。
1.4 数据处理
利用SPSS 21.0计算平均值及标准差等,对不同品种(系)的木薯各农艺性状进行ANOVA分析及Pearson分析,分析不同木薯品种(系)农艺性状的差异及相关性。用R语言和SPSS软件进行主成分分析(principal component analysis,PCA),使用Origin 2021和Excel 2010绘制图表。
2 结果与分析
2.1 各木薯品种(系)农艺性状分析
由表2可知,除落叶高度和块根粗无显著差异外(P>0.05),其余的农艺性状各品种(系)间存在显著差异(P<0.05)。株高、落叶高度、第1分枝高、地上鲜重和鲜薯个数最大的品种(系)分别为SG-9、GMT、SG-9、SC-1和GMT,最小均为SC9。主茎粗和块根粗最大均为SC124,最小均为SG-9,GMT的块根长与单株产量最大,GR891最小。综合看来,GMT具有较大的单株产量。
表2 不同品种(系)木薯各农艺性状比较
Table 2
品种(系) Variety (line) | 株高Plant height (cm) | 主茎粗Stem diameter (mm) | 第1分枝高First branch height (cm) | |||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
M±SD | CV (%) | M±SD | CV (%) | M±SD | CV (%) | |||||||||||||||||||||
277 | 213.43±44.65ab | 20.92 | 25.93±7.93a | 30.60 | 102.20±24.58abc | 24.05 | ||||||||||||||||||||
43-3 | 209.10±55.63ab | 26.60 | 24.97±9.11a | 36.47 | 92.73±33.62bc | 36.26 | ||||||||||||||||||||
58-7 | 218.80±59.16ab | 27.04 | 25.59±9.64a | 37.69 | 98.17±40.20abc | 40.95 | ||||||||||||||||||||
GMT | 224.23±45.10a | 20.11 | 23.84±13.05ab | 54.74 | 109.70±37.37ab | 34.07 | ||||||||||||||||||||
GR891 | 235.10±51.10a | 21.73 | 25.86±8.81a | 34.08 | 101.57±34.84abc | 34.30 | ||||||||||||||||||||
SC-1 | 223.43±59.49a | 26.62 | 26.54±8.94a | 33.69 | 107.37±37.38ab | 34.82 | ||||||||||||||||||||
SC124 | 227.67±58.98a | 25.91 | 26.63±9.15a | 34.35 | 103.17±39.74abc | 38.51 | ||||||||||||||||||||
SC205 | 212.47±60.36ab | 28.41 | 24.71±9.37ab | 37.93 | 92.87±39.44bc | 42.46 | ||||||||||||||||||||
SC9 | 201.93±61.99b | 30.70 | 24.12±9.46ab | 39.24 | 86.80±37.89c | 43.65 | ||||||||||||||||||||
SG-9 | 231.03±69.68a | 30.16 | 23.65±4.71b | 19.92 | 115.30±39.61a | 34.36 | ||||||||||||||||||||
平均Average | - | 25.82 | - | 35.87 | - | 36.34 | ||||||||||||||||||||
品种(系) Variety (line) | 株高Plant height (cm) | 主茎粗Stem diameter (mm) | 第1分枝高First branch height (cm) | |||||||||||||||||||||||
M±SD | CV (%) | M±SD | CV (%) | M±SD | CV (%) | |||||||||||||||||||||
平均Average | - | 25.82 | - | 35.87 | - | 36.34 | ||||||||||||||||||||
277 | 146.93±49.71a | 33.83 | 2.35±1.06b | 45.11 | 5.50±2.33ab | 42.36 | ||||||||||||||||||||
43-3 | 139.90±58.60a | 41.89 | 2.85±1.79ab | 62.95 | 5.67±3.00ab | 52.87 | ||||||||||||||||||||
58-7 | 145.10±66.39a | 45.75 | 2.99±2.57ab | 86.09 | 5.97±3.98ab | 66.63 | ||||||||||||||||||||
GMT | 154.87±63.40a | 40.93 | 2.83±2.06ab | 72.69 | 6.80±4.37a | 64.21 | ||||||||||||||||||||
GR891 | 147.47±59.13a | 40.10 | 2.93±1.65ab | 56.18 | 6.03±2.75ab | 45.57 | ||||||||||||||||||||
SC-1 | 152.90±63.31a | 41.41 | 3.51±2.08a | 59.29 | 5.93±3.11ab | 52.39 | ||||||||||||||||||||
SC124 | 148.60±64.46a | 43.38 | 3.21±2.01ab | 62.62 | 6.23±3.76ab | 60.30 | ||||||||||||||||||||
SC205 | 142.27±63.81a | 44.85 | 2.72±1.81ab | 66.51 | 5.50±3.09ab | 56.24 | ||||||||||||||||||||
SC9 | 129.90±65.12a | 50.13 | 2.13±1.77b | 82.91 | 4.83±3.08b | 63.66 | ||||||||||||||||||||
SG-9 | 154.33±61.65a | 39.95 | 2.42±1.58ab | 65.41 | 5.67±2.50ab | 44.02 | ||||||||||||||||||||
平均Average | 42.22 | 65.98 | 54.83 | |||||||||||||||||||||||
品种(系) Variety (line) | 株高Plant height (cm) | 主茎粗Stem diameter (mm) | 第1分枝高First branch height (cm) | |||||||||||||||||||||||
M±SD | CV (%) | M±SD | CV (%) | M±SD | CV (%) | |||||||||||||||||||||
277 | 31.13±10.23b | 32.87 | 37.53±8.09a | 21.57 | 1.89±0.90ab | 47.57 | ||||||||||||||||||||
43-3 | 29.43±6.96b | 23.65 | 36.56±9.68a | 26.47 | 1.72±0.97b | 56.57 | ||||||||||||||||||||
58-7 | 34.43±12.29ab | 35.70 | 37.19±9.76a | 26.25 | 2.22±1.87ab | 84.19 | ||||||||||||||||||||
GMT | 38.87±14.52a | 37.37 | 35.27±14.63a | 41.49 | 2.67±1.96a | 73.56 | ||||||||||||||||||||
GR891 | 29.30±9.00b | 30.72 | 37.46±9.40a | 25.10 | 1.71±1.17b | 68.42 | ||||||||||||||||||||
SC-1 | 31.10±9.39b | 30.18 | 38.13±9.83a | 25.77 | 1.89±1.43ab | 75.87 | ||||||||||||||||||||
SC124 | 33.90±14.58ab | 43.01 | 38.23±9.82a | 25.69 | 2.17±2.00ab | 92.17 | ||||||||||||||||||||
SC205 | 31.20±6.76b | 21.66 | 36.31±9.86a | 27.16 | 1.90±1.16ab | 61.21 | ||||||||||||||||||||
SC9 | 34.30±12.25ab | 35.71 | 35.72±9.77a | 27.34 | 2.20±1.85ab | 83.76 | ||||||||||||||||||||
SG-9 | 34.23±10.48ab | 30.63 | 35.25±7.82a | 22.18 | 2.21±1.09ab | 49.55 | ||||||||||||||||||||
平均Average | 32.15 | 26.90 | 69.29 |
M±SD为平均值±标准差,CV为变异系数,不同小写字母表示在0.05水平差异显著,下同
M±SD is mean ± standard deviation, CV is the coefficient of variation, different lowercase letters indicate significant difference at the level of 0.05, the same below
不同性状平均变异系数(表2)表明,单株产量>地上鲜重>鲜薯个数>落叶高度>第1分枝高>主茎粗>块根长>块根粗>株高。从不同品种(系)来看,277、SG-9和GR891农艺性状的变异较小,SC9、58-7和GMT的变异较大。
2.2 木薯农艺性状的相关性分析
表3 木薯农艺性状的相关性分析
Table 3
性状 Trait | 株高 Plant height | 主茎粗 Stem diameter | 第1分枝高 First branch height | 落叶高度 Deciduous height | 地上鲜重 Aboveground fresh weight | 鲜薯个数 Number of fresh cassava | 块根长 Roots length | 块根粗 Roots thick | 单株产量 Yield per plant |
---|---|---|---|---|---|---|---|---|---|
株高Plant height | 1.000 | ||||||||
主茎粗Stem diameter | 0.852** | 1.000 | |||||||
第1分枝高 First branch height | 0.901** | 0.806** | 1.000 | ||||||
落叶高度Deciduous height | 0.909** | 0.884** | 0.930** | 1.000 | |||||
地上鲜重 Aboveground fresh weight | 0.736** | 0.773** | 0.724** | 0.782** | 1.000 | ||||
鲜薯个数 Number of fresh cassava | 0.818** | 0.874** | 0.818** | 0.866** | 0.769** | 1.000 | |||
块根长Root length | 0.422** | 0.432** | 0.470** | 0.449** | 0.454** | 0.521** | 1.000 | ||
块根粗Root thick | 0.856** | 0.866** | 0.815** | 0.821** | 0.695** | 0.798** | 0.449** | 1.000 | |
单株产量Yield per plant | 0.691** | 0.739** | 0.704** | 0.753** | 0.669** | 0.897** | 0.891** | 0.884** | 1.000 |
“**”表示在0.01水平上极显著相关
“**”indicates extremely significant correlation at the level of 0.01
2.3 不同木薯品种(系)农艺性状的主成分分析
对不同木薯品种(系)的株高(X1)、主茎粗(X2)、第1分枝高(X3)、落叶高度(X4)、地上鲜重(X5)、鲜薯个数(X6)、块根长(X7)、块根粗(X8)和单株产量(X9)9个农艺性状进行主成分分析。结果(图1)显示,提取的2个主成分的累积方差贡献率达88.1%(图1a),表明提取的2个主成分可以代表测定的9个农艺性状指标的绝大部分信息,因此,可将9个性状综合成2个主成分。第1主成分解释了方差变异的77.0%,各农艺性状与PC1均呈正相关关系,第1主成分主要与鲜薯个数、地上鲜重和第1分枝高等有关,其中,鲜薯个数是第1主成分的主导变量。可将第1主成分称为生长因子。第2主成分解释了方差变异的11.1%,主要与块根长、单株产量等有关,其中,块根长是第2主成分的主导变量。第2主成分集中反映了产量状况,将第2主成分称为产量因子。
图1
图1
不同品种(系)木薯农艺性状PCA分析
Fig.1
PCA analysis of agronomic traits of different cassava varieties (lines)
主成分分析可以将多组数据的差异反映在二维坐标图中。由图1b可知,SG-9、GMT与SC9大部分位于第1、2象限,277和43-3大部分位于第2象限,58-7、GR891、SC-1、SC124和SC205分布在第3和4象限,各品种(系)间的农艺性状具有一定差异,也具有一定相似性。总体看来,GMT与其余品种的差异较大。综上所述,高产木薯品种(系)选育时应着重考察块根性状。
2.4 得分方程建立
根据主成分与特征向量之间的关系,分别得到2个主成分的表达式:
Y1=0.35X1+0.35X2+0.35X3+0.36X4+0.32X5+0.35X6+0.24X7+0.34X8+0.33X9Y2=-0.21X1-0.16X2-0.15X3-0.16X4-0.07X5-0.05X6+0.77X7-0.18X8+0.49X9
式中,Y1、Y2是单个主成分得分值;X1~X9是每个木薯农艺性状指标的标准化处理的数值。将每个木薯农艺性状指标的标准化处理数据代入方程式计算出Y1、Y2,再根据Y1、Y2各自的方差贡献率与2个成分累计贡献率的比值为权重系数,建立综合评分模型为Y=0.8737Y1+0.1263Y2,计算出10个不同木薯品种(系)的综合得分并排序,得到表4。
表4 10个木薯品种(系)主成分因子得分及排名
Table 4
品种 (系) Variety (line) | 主成分因子得分 Principal component factor score | 综合得分 Composite scores | 排名 Ranking | ||
---|---|---|---|---|---|
Y1 | Y2 | Y | |||
SG-9 | 13.492 | 0.097 | 11.800 | 1 | |
GMT | 8.573 | 0.577 | 7.563 | 2 | |
SC-1 | 6.240 | -0.306 | 5.414 | 3 | |
SC124 | 2.389 | -0.005 | 2.087 | 4 | |
277 | 0.984 | -0.158 | 0.840 | 5 | |
GR891 | 0.593 | -0.450 | 0.461 | 6 | |
58-7 | -2.521 | 0.160 | -2.182 | 7 | |
SC205 | -7.876 | -0.068 | -6.890 | 8 | |
43-3 | -8.056 | -0.246 | -7.070 | 9 | |
SC9 | -13.818 | 0.396 | -12.023 | 10 |
由表4可知,参试的10个木薯品种(系)中,综合得分排名前3的分别是SG-9、GMT和SC-1,得分依次为11.800、7.563和5.414。277和GR891排名居中,58-7、SC205、43-3和SC9的综合得分较低。综合看来,SG-9的综合得分最高,GMT和SC9的产量优势明显。
2.5 不同木薯品种(系)农艺性状聚类分析
图2
图2
木薯品种(系)农艺性状聚类分析图
Fig.2
Cluster analysis diagram of agronomic traits of cassava varieties (lines)
表5 3个类群木薯的农艺性状特征表
Table 5
性状 Trait | 类群ⅠGroupⅠ | 类群ⅡGroupⅡ | 类群ⅢGroup Ⅲ | |||||
---|---|---|---|---|---|---|---|---|
M±SD | CV (%) | M±SD | CV (%) | M±SD | CV (%) | |||
株高Plant height (cm) | 220.00±55.75ab | 25.34 | 227.63±58.29a | 25.61 | 201.93±61.99b | 30.70 | ||
主茎粗Stem diameter (mm) | 25.75±8.90a | 34.57 | 23.75±9.73a | 40.96 | 24.12±9.46a | 39.24 | ||
第1分枝高First branch height (cm) | 99.72±35.89ab | 35.99 | 112.50±38.29a | 34.03 | 86.80±37.89b | 43.65 | ||
落叶高度Deciduous height (cm) | 146.17±60.25ab | 41.22 | 154.60±62.00a | 40.10 | 129.90±65.12b | 50.13 | ||
地上鲜重Aboveground fresh weight (kg) | 2.94±1.91a | 64.80 | 2.63±1.83ab | 69.62 | 2.13±1.77b | 82.91 | ||
鲜薯个数Number of fresh cassava | 5.83±3.15ab | 54.08 | 6.23±3.57a | 57.34 | 4.83±3.08b | 63.66 | ||
块根长Root length (cm) | 31.50±10.24b | 32.52 | 36.55±12.77a | 34.95 | 34.30±12.25ab | 35.71 | ||
块根粗Root thick (mm) | 37.34±9.40a | 25.17 | 35.26±11.63a | 32.99 | 35.72±9.77a | 27.34 | ||
单株产量Yield per plant (kg) | 1.93±1.41b | 72.90 | 2.44±1.59a | 65.25 | 2.21±1.85ab | 83.76 |
3 讨论
主成分分析是利用降维的思想,把多个指标转化为少数几个综合指标,用较少的几项综合性指标对目标对象进行综合评价。本文通过对不同木薯品种(系)的主要农艺性状指标进行主成分分析,最终得到2个主成分,鲜薯个数是第1主成分的主导变量,块根长是第2主成分的主导变量。谢向誉等[24]在木薯单株产量与主要农艺性状的相关性研究中也指出,单株产量主要由块根数、最长薯长、生物产量等决定,与本文存在不同程度的一致性。
通过评分模型,得到各木薯品种(系)的综合得分,发现SG-9的综合得分最高,GMT和SC9的产量优势明显。进一步进行聚类分析,在欧氏距离为15时,参试木薯可分成3个类群,类群Ⅰ(低产群体)主要特点为主茎粗、块根粗、地上鲜重大。类群Ⅱ(高产群体)主要特点为具有较高的株高、第1分枝高、落叶高,鲜薯个数多、块根长、产量高,可优先作为推广种植品种。类群Ⅲ(中产群体)主要特点为高度矮,主茎粗、块根长与粗适中,单株产量较高,可作为推广种植的备选品种。
4 结论
参试的10个不同木薯品种(系)中,SG-9的综合得分最高,GMT和SC9的产量优势明显,可作为种植推广的品种(系)。单株产量与鲜薯个数、块根长、块根粗相关性最强,是选育高产品种首要考虑指标。单株产量、地上鲜重和鲜薯个数的变异系数均较大,在品种遗传改良时可作为优先考虑的农艺性状指标。
参考文献
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Cassava biology and physiology
,Cassava or manioc (Manihot esculenta Crantz), a perennial shrub of the New World, currently is the sixth world food crop for more than 500 million people in tropical and sub-tropical Africa, Asia and Latin America. It is cultivated mainly by resource-limited small farmers for its starchy roots, which are used as human food either fresh when low in cyanogens or in many processed forms and products, mostly starch, flour, and for animal feed. Because of its inherent tolerance to stressful environments, where other food crops would fail, it is often considered a food-security source against famine, requiring minimal care. Under optimal environmental conditions, it compares favorably in production of energy with most other major staple food crops due to its high yield potential. Recent research at the Centro Internacional de Agricultura Tropical (CIAT) in Colombia has demonstrated the ability of cassava to assimilate carbon at very high rates under high levels of humidity, temperature and solar radiation,which correlates with productivity across all environments whether dry or humid. When grown on very poor soils under prolonged drought for more than 6 months, the crop reduce both its leaf canopy and transpiration water loss, but its attached leaves remain photosynthetically active, though at greatly reduced rates. The main physiological mechanism underlying such a remarkable tolerance to drought was rapid stomatal closure under both atmospheric and edaphic water stress, protecting the leaf against dehydration while the plant depletes available soil water slowly during long dry periods. This drought tolerance mechanism leads to high crop water use efficiency values. Although the cassava fine root system is sparse, compared to other crops, it can penetrate below 2 m soil,thus enabling the crop to exploit deep water if available. Leaves of cassava and wild Manihot possess elevated activities of the C4 enzyme PEP carboxylase but lack the leaf Kranz anatomy typical of C4 species, pointing to the need for further research on cultivated and wild Manihot to further improve its photosynthetic potential and yield,particularly under stressful environments. Moreover, a wide range in values of Km (CO2) for the C3 photosynthetic enzyme Rubisco was found among cassava cultivars indicating the possibility of selection for higher affinity to CO2, and consequently higher leaf photosynthesis. Several plant traits that may be of value in crop breeding and improvement have been identified, such as an extensive fine root system, long leaf life, strong root sink and high leaf photosynthesis. Selection of parental materials for tolerance to drought and infertile soils under representative field conditions have resulted in developing improved cultivars that have high yields in favorable environments while producing reasonable and stable yields under stress.
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Contents 50 I. 50 II. 52 III. 54 IV. 55 V. 57 VI. 57 VII. 59 60 References 61 SUMMARY: As a consequence of an increase in world population, food demand is expected to grow by up to 110% in the next 30-35 yr. The population of sub-Saharan Africa is projected to increase by > 120%. In this region, cassava (Manihot esculenta) is the second most important source of calories and contributes c. 30% of the daily calorie requirements per person. Despite its importance, the average yield of cassava in Africa has not increased significantly since 1961. An evaluation of modern cultivars of cassava showed that the interception efficiency (ɛ ) of photosynthetically active radiation (PAR) and the efficiency of conversion of that intercepted PAR (ɛ ) are major opportunities for genetic improvement of the yield potential. This review examines what is known of the physiological processes underlying productivity in cassava and seeks to provide some strategies and directions toward yield improvement through genetic alterations to physiology to increase ɛ and ɛ. Possible physiological limitations, as well as environmental constraints, are discussed.© 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.
Information resoureces for cassava research and breeding
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International research on cassava photosynthesis,productivity,eco-physiology,and responses to environmental streses in the tropics
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