小麦抗倒性研究进展

倒伏是严重影响小麦子粒产量和品质的一个重要因素。本文系统阐述了小麦茎秆形态和结构特性、茎秆化学成分与抗倒伏关系以及抗倒性的遗传和分子标记等方面的最新研究进展。株高、基部节间长度与抗倒性呈负相关;而基部节间粗度、秆壁厚、单位长度干重与抗倒性呈正相关。茎秆机械组织细胞层数、厚度,维管束数目、面积以及髓腔大小与抗倒性密切相关。茎秆化学成分中纤维素、木质素以及碳水化合物含量和硅、钾元素含量与抗倒性呈正相关。小麦抗倒性呈数量性状遗传特征,除受多对主基因控制外,可能还受微效修饰基因作用。采用分子标记技术已将抗倒性以及与抗倒性相关的茎秆形态性状进行了QTL定位。     

Quantitative trait loci for lodging resistance in a segregating wheat×spelt population

 Lodging can strongly affect both the grain yield and the quality of wheat. Lodging represents a quantitative trait and is difficult to assess on a phenotypic basis. Marker-assisted selection (MAS) could therefore become an important tool in breeding for lodging resistance. In this study, we mapped and characterised quantitative trait loci (QTLs) for lodging resistance, as well as morphological traits correlated with lodging, in a segregating population of 226 recombinant inbred lines derived from the cross of the lodging-resistant wheat variety Forno with the susceptible spelt variety Oberkulmer. Lodging, plant height, leaf width, leaf-growth habit, culm stiffness, culm swinging, culm thickness, days to ear emergence and days to flowering were assessed in field trials at two locations in 1996 and at one location in 1997. Additionally, at one location weight and length parameters were also assessed. Plant height and culm stiffness explained 77% of the phenotypic variance of lodging in a multiple regression model over all three environments. QTL analysis of lodging and morphological parameters was based on a genetic map containing 230 loci with 23 linkage groups (2469 cM). With the method of composite interval mapping nine QTLs for lodging resistance were detected, explaining 63% of the phenotypic variance in a simultaneous fit. Seven of these QTLs coincided with QTLs for morphological traits, reflecting the correlations between these traits and lodging. In our population the most efficient way to improve lodging resistance would be by a combination of indirect selection on plant height and culm stiffness together with MAS on the two QTLs for lodging resistance which did not coincide with QTLs for morphological traits. Received: 3 August 1998 / Accepted: 28 November 1998     

不同小麦品种茎秆特性及其与抗倒性的关系

以黄淮麦区优良品种矮抗58、周麦18、豫麦49、百农418为研究对象,采用田间试验与实验室分析相结合的方法,对不同小麦品种在不同生育时期的抗倒伏性状进行研究.结果表明: 茎秆机械强度在开花期至花后20 d处于较高水平,在花后30 d明显下降;倒伏指数在开花期最小,花后30 d最大,其余两个时期处于中间水平.相关分析表明,开花期机械强度与重心高度呈显著负相关,与纤维素、木质素含量呈显著正相关,倒伏指数与节长、株高、重心高度呈显著正相关,与纤维素、木质素含量呈显著负相关;花后10 d和花后20 d机械强度与节长、株高、重心高度呈显著负相关,与茎粗、纤维素、半纤维素、木质素含量呈显著正相关,倒伏指数这段时期正好与之相反;花后30 d机械强度与株高、重心高度呈显著负相关,倒伏指数与株高、重心高度呈显著正相关,与木质素含量呈显著负相关.因此,明确各个生育时期与抗倒性相关的茎秆特性,可为黄淮麦区高产抗倒性品种的选育提供依据.     

Response of Fine Root Carbohydrate Content to Soil Nitrogen Addition and Its Relationship with Soil Factors in a Schrenk (Picea schrenkiana) Forest

Fine roots are vital for water and nutrient uptake in plants. Understanding the responses of metabolic traits to changing environmental conditions is critical, but little is known. In this study, the carbohydrate content of fine roots was characterized for six soil layers and three diameter classes in a Schrenk spruce (Picea schrenkiana) forest on the Tianshan Mountains of China. Soil nitrogen addition can influence carbohydrate content, but the degree is related to soil layer and fine root diameter. Specifically, as nitrogen (N) levels increased, the soluble sugar, cellulose, lignin and structural carbohydrate content (SC) all increased and then decreased; the starch and non-structural carbohydrate content (NSC) decreased gradually. In addition, N addition had significant effects on starch and cellulose content, as well as total carbohydrates. The interaction between root diameter and N addition also influenced soluble sugars, cellulose and NSC, while the three-way interaction among N addition, soil layer and diameter only affected cellulose content and NSC/SC. In the control treatment (no nitrogen addition), the following soil factors influenced fine root metabolism in order of decreasing importance: C:N, C:P, N:P, C, N, water content, bulk density, pH, conductivity, and P. In the N addition treatments, the soil conductivity, pH, and N content were strongly correlated with root metabolic characteristics.

     

套作大豆苗期茎秆纤维素合成代谢与抗倒性的关系

为从茎秆强度的角度研究套作大豆苗期对荫蔽胁迫的响应及耐荫抗倒机制,采用耐荫性不同的3个大豆材料,在玉米大豆套作和单作两种种植模式下,对茎秆的纤维素、可溶性糖、蔗糖、淀粉含量及蔗糖代谢中关键酶活性以及茎秆抗折力、抗倒伏指数等进行测定,研究它们与套作大豆苗期倒伏的关系.套作大豆苗期倒伏严重,茎秆抗折力、抗倒伏指数、纤维素、可溶性糖、蔗糖、淀粉含量和相关酶活性均显著低于单作.不同大豆材料受套作荫蔽影响程度不同,强耐荫性大豆南豆12茎秆抗折力降低幅度最小,在套作环境下其茎秆抗折力、抗倒伏指数大,纤维素、可溶性糖、蔗糖、淀粉含量高,酶活性强.相关分析表明： 套作大豆苗期茎秆糖含量均与抗折力呈极显著正相关,与倒伏率呈极显著负相关;蔗糖含量与蔗糖磷酸合酶(SPS)、蔗糖合酶(SS)、中性转化酶(NI)活性呈极显著正相关,与酸性转化酶(AI)活性相关性不显著;纤维素含量与SPS、SS呈极显著正相关,与NI呈显著正相关,与AI相关性不显著.套作环境下,强耐荫性大豆苗期茎秆中较高的SPS、SS活性是其维持高蔗糖和纤维素含量的酶学基础,而高纤维素含量有利于提高茎秆强度,进而增强其抗倒伏能力.本研究应用玉米大豆套作种植系统,从苗期抗倒角度,探明了光环境对不同基因型大豆茎秆纤维素代谢的影响机制,为下一步筛选耐荫抗倒大豆品种提供了理论依据.     

QTL analysis of lodging resistance and related traits in Italian ryegrass (<Emphasis Type="Italic">Lolium multiflorum</Emphasis> Lam.)

Italian ryegrass (Lolium multiflorum Lam.) is the most widely cultivated annual forage grass in Japan. Lodging damage reduces both harvested yield and forage quality. To identify the chromosomal regions controlling lodging resistance in Italian ryegrass, we analyzed seven quantitative characters—heading date, plant height, culm weight, culm diameter, culm strength, tiller number, and culm pushing resistance—and evaluated lodging scores in the field in a two-way pseudo-testcross F₁ population. Significant correlations between most combinations of the traits examined were found. Seventeen QTLs for all traits except culm weight were detected on six of seven linkage groups by simple interval mapping using cross-pollination (CP) algorithm, and 33 independent QTLs were also detected by composite interval mapping from both male and female parental linkage maps. In addition, up to 18 QTLs for lodging scores evaluated at nine different times were detected on all linkage groups. The flanking markers of those QTLs will serve as a useful tool for marker-assisted selection of lodging resistance in Italian ryegrass.     

Culm strength of barley : correlation among maximum bending stress, cell wall dimensions, and cellulose content

Grass culms are known to differ in breaking strength, but there is little physicochemical data to explain the response. The fourth internode of four brittle and two nonbrittle barley (Hordeum vulgare L.) strains were used for physical and chemical studies of culm strength. Inner and outer culm diameters of brittle strains (3.6 ± 0.2 and 5.0 ± 0.1 millimeters) were not significantly different from those of nonbrittle strains (3.9 ± 0.2 and 5.2 ± 0.2 millimeters). Maximum bending stress, at which the culm was broken, was 192 ± 34 g/mm² for brittle and 490 ± 38 g/mm² for nonbrittle strains. Wall thickness and cell dimensions of epidermal, sclerenchyma, and parenchyma cells were measured in culm cross sections. The area of cell wall per unit cell area for each tissue was significantly correlated with the maximum bending stress (r = 0.93 for epidermis, 0.90 for sclerenchyma, and 0.84 for parenchyma). Cell walls of brittle culms had 6 to 64% as much cellulose content as those of nonbrittle culms. Maximum bending stress correlated significantly with cellulose content of the cell walls (r = 0.93), but not with the contents of noncellulosic compounds. The lower cellulose content of the brittle culm was significantly correlated with brittleness.     

小麦种质抗倒性的评价和抗倒性状的相关与通径分析

对９６份小麦种质资源的抗倒性进行了鉴定评价,筛选出高抗型材料９份,其中４份是丰源,表明抗倒性能够与丰产性状很好地协调结合。对抗倒性状的相关分析表明,在株高相差较大的情况下,株高和重心高度对抗倒性十分重要。但在对株高相差不大的情况下,茎秆的机械强度是主要决定因素,对于株高较高的材料,重心高度对抗倒性有较大影响;对于较矮的材料,基部第一节间长度则较为重要。通径分析结果进一步表明,茎秆机械强度对抗倒性的     

Association of lignin and <Emphasis Type="Italic">FLEXIBLE CULM 1 (FC1)</Emphasis> ortholog in imparting culm strength and lodging resistance in kodo millet (<Emphasis Type="Italic">Paspalum scrobiculatum</Emphasis> L.)

To understand the lodging behavior in kodo millet (Paspalum scrobiculatum L.) at morphological, biochemical, and molecular levels, 22 germplasm accessions selected based on previous trials were characterized for culm strength-related morphological traits such as pulling force, culm weight per unit length, culm diameter, recovery angle after bending and degree of lodging, and biochemical traits such as cellulose, hemicellulose, and lignin content of the culm. Correlation among traits and path analysis with degree of lodging showed that only lignin content per unit length of the culm had a very high negative effect on degree of lodging, followed by culm diameter, which means that higher the lignin content and culm diameter, the lesser will be the degree of lodging. Hence, it was concluded that any improvement for lodging resistance in kodo millet can be achieved through improving the lignin content (mg/cm of the dry culm) and culm diameter. Gene expression studies in kodo millet for FLEXIBLE CULM 1 (FC1), a gene implicated in lignin biosynthetic pathway and lodging resistance in rice, suggests the role of FC1 gene ortholog in lignin accumulation in kodo millet as well. Accordingly, the highest gene expression was recorded in strong culm line “Adari” a land race and the lowest expression in “Aamo 10,” a weak culm line.     

Isolation,expression, and evolution analysis of the type 2C protein phosphatase gene <Emphasis Type="Italic">BcABI1</Emphasis> involved in abiotic and biotic stress in <Emphasis Type="Italic">Brassica campestris</Emphasis> ssp. <Emphasis Type="Italic">chinensis</Emphasis>

Dense plant cultivation is an efficient approach to utilize the maximum inputs for increasing maize production. However, dense plant populations may prone to lodging as it results in increased plant height and reduced culm diameter; therefore, we hypothesized that weaker stems may be responsible for maize lodging. In this study, we examined the regulatory effects of paclobutrazol under two commonly used application methods (seed-soaking and seed-dressing). Seed-soaking with paclobutrazol at the rate of 0 (CK1), 200 (S1), 300 (S2), and 400 (S3) mg L^?1, while seed-dressing at the rate of 0 (CK2), 1.5 (D1), 2.5 (D2), and 3.5 (D3) g kg^?1 were used. Results showed that paclobutrazol improved the culm physical strength by increasing the rind penetration strength, stalk breaking strength, culm diameter, wall thickness, and dry weight per unit length of basal third internode, compared to control plants. Moreover, paclobutrazol reduced the internode length, plant height, ear height, center of gravity height and lodging rate in both growing seasons. In addition, more lignin was accumulated in the basal internode and the activities of phenylalanine ammonia-lyase (PAL), peroxidase (POD), cinnamyl alcohol dehydrogenase (CAD) and 4-coumarate: CoA ligase (4CL) increased with paclobutrazol, and their maximum values were observed in the S2 and D3 treatments, resulting in strong lodging resistance. Lignin content was positively and significantly correlated with the rind penetration strength, breaking strength of internode, and activities of PAL, 4CL, POD, and CAD, while significantly and negatively correlated with lodging percentage. The present findings suggested that 300 mg L^?1 and 3.5 g kg^?1 of paclobutrazol may efficiently be utilized to minimize the risk of lodging, not only by manipulating plant height but also by enhancing culm physical strength and lignin accumulation in basal internodes.     

Sucrose Utilization via Invertase and Sucrose Synthase with Respect to Accumulation of Cellulose and Callose Synthesis in Wheat Roots under Oxygen Deficiency

The sucrose cleavage by sucrose synthase (SuSy) and neutral invertase was studied in wheat roots (Triticum aestivum L.) subjected to hypoxia or anoxia for 4 days. By in situ activity staining, increased SuSy activity was observed in the tip region and stele of root axes while the activity of invertase decreased. Cellulose content significantly increased in hypoxically treated roots. The cellulose deposition was correlated with regions of high SuSy activity, being mainly located in the pericycle and endodermis. Invertase activity was distributed along the root without clear difference between cortex and stele. Under root hypoxia, a significant increase in the structural carbohydrates, callose and especially cellulose, was shown. Increasing levels of soluble carbohydrates were partially used to synthesize cellulose for secondary wall thickening and callose to counteract the tissue injury following low-oxygen stress. Under strict anoxia, the roots were much more injured but sustained a high level of cellulose and callose while the soluble carbohydrates almost disappeared.     

水稻脆秆突变体bc-s1的表型分析和基因定位

茎秆机械强度影响植株抗倒伏能力, 是备受关注的重要农艺性状之一。与野生型相比, 水稻(Oryza sativa)脆秆隐性突变体bc-s1茎秆抗折力和抗张力分别降低31.1%和67.2%, 茎秆纤维素和木质素含量分别降低24.97%和增高38.82%。细胞学分析显示, bc-s1茎秆厚壁细胞发生不规则变化, 次生壁增厚受阻。通过图位克隆和测序分析, 初步确定bc-s1突变体中纤维素合成酶催化亚基Os09g25490/OsCesA9基因第1外显子的第28个碱基G突变为A。该等位突变体的获得为进一步揭示OsCesA9调控细胞壁建成的生物学功能提供了新的研究材料。     

小麦抗倒性状的基因效应及杂种优势分析

采用Ｈａｙｍａｎ双列分析较为系统地研究了抗倒性状的基因效应,并进行了杂种优势分析。结果表明,小麦抗倒性状的遗传以效应和显微效应为主,且以显著性效较为重要。     

DiSC (direct saccharification of culms) process for bioethanol production from rice straw

A simple process (the direct-saccharification-of-culms (DiSC) process) to produce ethanol from rice straw culms, accumulating significant amounts of soft carbohydrates (SCs: glucose, fructose, sucrose, starch and β-1,3-1,4-glucan) was developed. This study focused on fully mature culms of cv. Leafstar, containing 69.2% (w/w of dried culms) hexoses from SCs and cellulose. Commercially-available wind-separation equipment successfully prepared a culm-rich fraction with a SC recovery of 83.1% (w/w) from rice straw flakes (54.1% of total weight of rice straw). The fraction was suspended in water (20%, w/w) for starch liquefaction, and the suspension was subjected to a simultaneous saccharification and fermentation with yeast, yielding 5.6% (w/v) ethanol (86% of the theoretical yield from whole hexoses in the fraction) after 24 h fermentation. Thus, the DiSC process produced highly-concentrated ethanol from rice straw in a one vat process without any harsh thermo-chemical pretreatments.     

作物抗倒伏相关性状及其信号转导调控机理的研究进展

倒伏是影响作物品种选育和产业化推广的重要限制因子,会使作物籽粒与秸秆的产量和品质显著降低且易引发病虫害,不利于机械化收割使作物经济效益显著降低.株高、茎秆强度、壁厚、分蘖数、分蘖夹角等性状同作物茎秆抗倒伏特性密切相关.倒伏主要分为为根倒伏和茎倒伏,茎倒伏与茎秆特性相关,其中株高与分蘖数分别受赤霉素信号转导和独脚金内酯信...     

Intrinsic morphology and spatial distribution of non-structural carbohydrates contribute to drought resistance of two mulberry cultivars

• Drought is one of the most adverse environmental stresses limiting plant growth and productivity. However, the underlying mechanisms regarding metabolism of non-structural carbohydrates (NSC) in source and sink organs are still not fully elucidated in woody trees.
• Saplings of mulberry cv Zhongshen1 and Wubu were subjected to a 15-day progressive drought stress. NSC levels and gene expression involved in NSC metabolism were investigated in roots and leaves. Growth performance and photosynthesis, leaf stomatal morphology, and other physiological parameters were also analysed.
• Under well-watered conditions, Wubu had a higher R/S, with higher NSC in leaves than in roots; Zhongshen1 had a lower R/S with higher NSC in roots than leaves. Under drought stress, Zhongshen1 showed decreased productivity and increased proline, abscisic acid, ROS content and activity of antioxidant enzymes, while Wubu sustained comparable productivity and photosynthesis. Interestingly, drought resulted in decreased starch and slightly increased soluble sugars in leaves of Wubu, accompanied by notable downregulation of starch-synthesizing genes and upregulation of starch-degrading genes. Similar patterns in NSC levels and relevant gene expression were also observed in roots of Zhongshen1. Concurrently, soluble sugars decreased and starch was unchanged in roots of Wubu and leaves of Zhongshen1. However, gene expression of starch metabolism in roots of Wubu was unaltered, but in leaves of Zhongshen1 starch metabolism was more activated.
• These findings revealed that intrinsic R/S and spatial distribution of NSC in roots and leaves concomitantly contribute to drought resistance in mulberry.

     

Locus prl5 improves lodging resistance of rice by delaying senescence and increasing carbohydrate reaccumulation.

We investigated the reason for carbohydrate retention in the stem of rice (Oryza sativa L.) at full-ripe stage in a near-isogenic line (NIL63) carrying prl5, which confers lodging resistance without yield loss. NIL63 showed higher lodging resistance than Nipponbare (control) without reduced yield. At heading, the carbohydrate content in the NIL63 stem (culm and leaf sheathes) was the same as in Nipponbare. At 2 weeks after heading, the carbohydrate content in NIL63 was significantly higher than in Nipponbare. At 4 weeks after heading, the carbohydrate content in NIL63 had decreased to near the level in Nipponbare. At 6 weeks after heading, NIL63 showed higher carbohydrate reaccumulation. Chlorophyll degradation in the leaf blades of NIL63 was slower, and the chlorophyll content at 6 weeks after heading was higher than in Nipponbare. These results suggest that the delay in leaf senescence by prl5 results in carbohydrate reaccumulation in the stem after grain filling, increasing lodging resistance.     

Activities of fructan- and sucrose-metabolizing enzymes in wheat stems subjected to water stress during grain filling

This study investigated if a controlled water deficit during grain filling of wheat (Triticum aestivum L.) could accelerate grain filling by facilitating the remobilization of carbon reserves in the stem through regulating the enzymes involved in fructan and sucrose metabolism. Two high lodging-resistant wheat cultivars were grown in pots and treated with either a normal (NN) or high amount of nitrogen (HN) at heading time. Plants were either well-watered (WW) or water-stressed (WS) from 9 days post anthesis until maturity. Leaf water potentials markedly decreased at midday as a result of water stress but completely recovered by early morning. Photosynthetic rate and zeatin + zeatin riboside concentrations in the flag leaves declined faster in WS plants than in WW plants, and they decreased more slowly with HN than with NN when soil water potential was the same, indicating that the water deficit enhanced, whereas HN delayed, senescence. Water stress, both at NN and HN, facilitated the reduction in concentration of total nonstructural carbohydrates (NSC) and fructans in the stems but increased the sucrose level there, promoted the re-allocation of pre-fixed ¹⁴C from the stems to grains, shortened the grain-filling period, and accelerated the grain-filling rate. Grain weight and grain yield were increased under the controlled water deficit when HN was applied. Fructan exohydrolase (FEH; EC 3.2.1.80) and sucrose phosphate synthase (SPS; EC 2.4.1.14) activities were substantially enhanced by water stress and positively correlated with the total NSC and fructan remobilization from the stems. Acid invertase (EC 3.2.1.26) activity was also enhanced by the water stress and associated with the change in fructan concentration, but not correlated with the total NSC remobilization and ¹⁴C increase in the grains. Sucrose:sucrose fructosyltransferase (EC 2.4.1.99) activity was inhibited by the water stress and negatively correlated with the remobilization of carbon reserves. Sucrose synthase (EC 2.4.1.13) activity in the stems decreased sharply during grain filling and showed no significant difference between WW and WS treatments. Abscisic acid (ABA) concentration in the stem was remarkably enhanced by water stress and significantly correlated with SPS and FEH activities. Application of ABA to WW plants yielded similar results to those for WS plants. The results suggest that the increased remobilization of carbon reserves by water stress is attributable to the enhanced FEH and SPS activities in wheat stems, and that ABA plays a vital role in the regulation of the key enzymes involved in fructan and sucrose metabolism.Abbreviations ABA Abscisic acid - DAS Days after sowing - DPA Days post anthesis - ESC Ethanol-soluble carbohydrate - FEH Fructan exohydrolase - HN High amount of nitrogen - INV Invertase - NN Normal amount of nitrogen - NSC Nonstructural carbohydrate - _leaf Leaf water potential - _soil Soil water potential - Pr Photosynthetic rate - SPS Sucrose phosphate synthase - SS Sucrose synthase - SST Sucrose:sucrose fructosyltransferase - V_limit Limiting substrate - V_max Saturated substrate - WS Water stressed - WSC Water-soluble carbohydrate - WW Well watered - Z Zeatin - ZR Zeatin riboside     

Response of sugar metabolism in the cotyledons and roots of Ricinus communis subjected to salt stress

• Ricinus communis is an important oilseed crop worldwide and is also considered one of the best potential plants for salt-affected soil improvement in northeast China. However, little is known about photosynthesis and carbohydrate metabolism in this plant, nor the distribution of carbohydrates in cotyledons and roots under salinity stress.
• In the present study, seedling growth, gas exchange parameters (P_N, E, g_s and C_i), carbohydrate (fructose, sucrose, glucose, soluble sugar and starch) metabolism and related enzymes and genes were measured in Ricinus plants.
• Under salt stress, P_N of cotyledons decreased significantly (P < 0.05), resulting in weak photosynthetic capacity. Furthermore, salt stress increased sucrose and glucose content in cotyledons, but decreased soluble sugar and starch content. However, sucrose increased and starch decreased in roots. This may be correlated with the increasing sugar metabolism under salinity, including notable changes in sugar-related enzyme activities (SPS, SuSy, α-amylase and β-amylase) and gene expression of RcINV, RcSUS, RcAmY, RcBAM and RcGBE1.
• The results suggest that salinity reduces photosynthesis of cotyledons, alters carbohydrate allocation between cotyledons and roots and also promotes starch utilization in cotyledons and starch biosynthesis in roots, leading to a functional imbalance between cotyledons and roots. Together, these findings provide insights into the crucial role of sugar metabolism in improving salt-tolerance of Ricinus during the early seedling growth stage.

     

Improvement of lodging resistance with QTLs for stem diameter in rice (Oryza sativa L.)

Varietal differences among ten rice cultivars showed that stem diameter is a key factor in lodging resistance (measured in terms of pushing resistance). Two near-isogenic lines (NILs) were selected from a series of chromosome segment substitution lines developed between cultivars Nipponbar and Kasalath, one containing a single stem diameter QTL (sdm8; NIL114), and another with four stem diameter QTLs (sdm1, sdm7, sdm8, sdm12; NIL28). Compared with the Nipponbare control, stem diameters were larger in NIL114 and NIL28 by about 7 and 39%, respectively. Pushing resistance in NIL28 was significantly greater than in Nipponbare, but NIL114 was similar to Nipponbare. The two NILs had greater weight of lower stem and culm wall thickness than Nipponbare. NIL28 had higher plant height, which is a negative effect on lodging resistance, than Nipponbare. The non-structural carbohydrate contents of NIL stems were higher than that of Nipponbare, whereas the silicon contents were lower in the NILs, and cellulose contents were lower only in NIL28. The basal internodes of the two NILs were significantly stiffer than those of Nipponbare. These results suggest that increasing stem diameter in rice breeding programs would improve lodging resistance, although the combination of multiple QTLs would be necessary to produce thicker stems with higher pushing resistance, whereas the higher plant height could also result from the combination of multiple QTLs.