Modification of plant height via RNAi suppression of OsGA20ox2 gene in rice

GA 20-oxidase (GA20ox) is a regulatory enzyme for the syntheses of biologically active GAs in plants. The loss-of-function mutations in OsGA20ox2 of rice (Oryza sativa L.) generate the well-known Green Revolution gene sd-1, which cause the semi-dwarfism phenotype. In our present investigation, semi-dwarf plants were generated from a taller rice variety QX1 by RNAi suppression on the expression of OsGA20ox2. The 531bp-fragment of OsGA20ox2 was amplified by PCR from genomic DNA of QX1 and used to construct the hairpin RNAi vector pCQK2. The wild type QX1 was transformed with pCQK2 by Agrobacterium-mediated transformation and some independent transgenic RNAi lines exhibited semi-dwarfism. RT-PCR and Northern blot analyses showed that the expression of OsGA20ox2 was specifically suppressed in the RNAi semi-dwarf lines. Endogenous GA assays revealed that the contents of the GA20ox2-catalyzed products GA₁₉, GA₂₀ and the down-stream biologically active GA₁ were drastically reduced in the RNAi semi-dwarf lines. We further showed that the RNAi semi-dwarf lines could be restored to normal plant height by applying exogenous GA₃. The results indicated that the semi-dwarfism of the RNAi semi-dwarf lines was associated with the decreased expression of OsGA20ox2 gene and the reduced content of endogenous biologically active GA₁. Analyses of panicle length, seeds per panicle and 1000-grain weight suggested that the RNAi semi-dwarf lines showed stable grain yield compared with the wild type plants. It is demonstrated that the RNAi approach could be useful for plant breeding purposes in the future. Qing Yang, Chun-Lian Wang have contributed equally to this work.     

Field-specific variable rate fertilizer application based on rice growth diagnosis and soil testing for high quality rice production

This study was carried out to verify the applicability of variable rate fertilization (VRF) based on soil testing and diagnosis of rice plant growth for high quality rice production of var. Chucheongbyeo at the farm level. The field trials were conducted at Icheon in Gyeonggi province on a 10 ha farm consisting of 45 experimental fields. For comparative study, 15 field trials were carried out adopting fertilizer management (FPM) practices currently used by farmers. FPM fields were managed by each rice grower using current cultivation methods, but in each VRF field fertilizer application was prescribed using soil test results and the amount of N fertilizer for top-dressing at panicle initiation stage was calculated using rice growth value at that stage. In VRF fields, the total amount of N fertilizer application was less (72 kg ha⁻¹) than that in FPM fields (103 kg ha⁻¹). However, the amount of K₂O fertilizer application was more in VRF fields (60 kg ha⁻¹) than that in FPM fields (52 kg ha⁻¹). The amount of P₂O₅ fertilizer application was similar between the VRF and FPM fields. Plant height was significantly shorter and the number of tillers was significantly more at VRF fields than at the FPM fields. Coefficient of variation (CV) of each growth characteristic measured in VRF was lower than that of FPM fields at panicle initiation stage. There was no difference in culm and panicle length and panicle number between them at the grain filling stage, but CV of panicle numbers per m² decreased in VRF compared with that of the FPM fields. Rice yield was not different between VRF and FPM fields despite higher brown rice recovery and 1,000-grain weight in VRF fields. Under VRF management, head rice yield increased due to an increase in head rice ratio accompanied by a reduction in brown rice protein content and variation of quality characteristics. These results suggest that VRF application based on soil tests and measurement of rice growth value at panicle initiation stage has the potential for quality control and production of high quality rice through increasing uniformity of growth and reducing the variability in quality among individual fields.     

Effect of light on endogenous levels of gibberellin and abscisic acid in seed germination of photoblastic weedy rice (Oryza sativa L.)

The effect of red (R) and R/far-red (FR) lights on endogenous gibberellin (GA) and abscisic acid (ABA) content was first investigated during the germination of photoblastic black-hulled weedy rice (PBWR) seeds. The R light-treated PBWR seeds germinated after 36–48 h and germination was increased to 63% at 72 h. However, the FR light-treated seeds after R light treatment, suppressed the R light effect showing only 11% germination even at 72 h after the light treatment. The PBWR seed treated with R light rapidly increased the endogenous level of GA₁ to about 200 times at 12 h before seed germination as compared with R/FR (control) which suppressed the effect of R light. The contents of other GAs like GA₁₂, GA₅₃, GA₁₉, GA₂₀, and GA₈ were not affected by the R light irradiation. These results showed that the major biosynthetic pathway of GAs in PBWR seeds is the early 13-hydroxylation pathway leading to GA₁, which was suggested to be physiologically active in the PBWR seed germination. The decrease in the level of ABA in the R light-treated seeds was greater than the R/FR light-treated seeds, indicating that the balance of endogenous GA1 and ABA is responsible for the induction of germination in the PBWR seed.     

氮肥水平和栽插密度对杂交稻茎秆理化特性与抗倒伏性的影响

以杂交稻金优527为材料,分别在中低海拔地区雅安(600 m)和高海拔地区西昌(1 590 m)进行了以氮肥水平为主区,栽插密度为副区的田间裂区试验。结果表明,随施氮量和栽插密度的增加,茎秆基部节间变细长,茎壁变薄,秆型指数降低,茎鞘中淀粉、纤维素、木质素含量降低,充实度变差;氮肥水平和栽插密度还影响茎秆中氮、钾、硅、钙、镁、铁、锌、铜、锰等矿质元素的含量,从而影响茎秆的倒伏指数和抗倒伏能力。水稻基部茎秆的倒伏指数与株高、重心高度和基部各伸长节间的长度及氮、镁含量正相关,与茎粗、茎壁厚、比茎重、秆型指数及淀粉、纤维素、木质素和钾、钙含量负相关,与茎秆硅含量呈二次函数关系,适宜的硅含量为4.5~4.8 mg kg^-1。由于生态条件不同,两试点水稻茎秆抗倒能力和受氮肥水平与栽插密度影响的程度存在一定差异,高产、抗倒栽培要因地制宜。金优527基部节间的临界倒伏指数为200。     

IAA、GA3和ABA对稻根负向光性和生长的影响

为探明稻根负向光性与内源植物激素含量的关系,以及外源激素对水稻根系生长的影响,以扬稻6号(籼稻)、日本晴(粳稻)和中花11 (粳稻)的OsPIN1a超表达转基因水稻为材料,观察了根负向光性生长的过程,分析了负向光弯曲部位内源生长素(IAA)、赤霉素(GA₃)和脱落酸(ABA)的含量,以及外源激素对水稻根系形态和解剖结构的影响。结果表明, 扬稻6号和日本晴的根都具有负向光性,扬稻6号侧根和不定根的负向光性大于日本晴;2种材料中,IAA、GA₃和ABA在发生负向光弯曲过程中的含量变化基本一致。光照引起3种激素的含量下降;向光侧的含量低于背光侧。单侧光照和外施IAA共同促进了籼稻根毛的大量发生;与普通水稻相比,OsPIN1a超表达稻株的根负向光性角度增大。外源GA₃和ABA处理与稻根负向光性间无直接关系;外源ABA处理显著抑制了根的生长,单株根系总吸收表面积与根数均减少。10 µmol L^-1 ABA处理的水稻根尖生长异常,分生区和根冠发育不良,细胞伸长受抑,成熟区细胞变形使根局部膨胀,并改变了中央维管组织的发育。     

矮杆和半矮杆大豆突变体植株生长对外源GA3的响应

矮杆和半矮杆突变体是研究植物基因功能和培育高产作物新品种的重要材料。本研究以矮杆和半矮杆大豆突变体与各自野生型品种为材料, 利用外源赤霉素(GA₃)处理不同发育时期植株, 研究植株生长速率和成熟期株高性状发育对外源GA₃的响应及主茎纵向细胞的形态学变化, 分析两类突变体与各自野生型之间的内源赤霉素含量差异。结果表明, 外源GA₃(40 mg L^-1)对半矮杆和矮杆突变体的作用效果明显不同, GA₃处理后半矮杆突变体植株在不同测定时段的平均生长速率达到2.76 cm d^-1, 而矮杆突变体的平均生长速率仅为0.92 cm d^-1, 而且成熟期半矮杆突变体植株的平均高度、主茎平均节间长度与节间纵向细胞长度均显著超过对照, 外源GA₃能够恢复其正常的野生型株高表型; 而矮杆突变体较对照的上述3项增幅均明显小于半矮杆型, 外源GA₃不能恢复其正常的野生型株高表型。说明半矮杆突变体的植株生长对外源GA₃有明显响应, 为GA₃敏感型突变体; 而矮杆突变体仅在生育前期对外源GA₃有一定程度响应, 为GA₃钝感型突变体。半矮杆和矮杆突变体成熟期植株的内源GA₃₊₁含量均显著低于各自野生型品种, 这可能是二者表型矮化的生理原因。     

Role of Nitrogen and Gibberellin (GA3) in the Regulation of Enzyme Activities and in Osmoprotectant Accumulation in Brassica juncea L. under Salt Stress

Salt stress alters a wide array of plant metabolic mechanisms. Different strategies of the application of nutrients and phytohormones are required to overcome the adverse effects of salt stress. The main objective of the present study was to determine if added nitrogen (N) and gibberellin (GA₃) in growth medium could alleviate the adverse effects of salt stress on plant metabolism. Two‐week‐old plants were fed with: (i) 0 mm NaCl + 0 mg N kg^?1 sand + 0 m GA₃ (control), (ii) 100 mm NaCl + 0 mg N kg^?1 sand + 0 m GA₃, (iii) 0 mm NaCl + 40 mg N kg^?1 sand + 0 m GA₃, (iv) 0 mm NaCl + 0 mg N kg^?1 sand + 10^?5 m GA₃, (v) 100 mm NaCl + 40 mg N kg^?1 sand + 0 m GA₃, (vi) 100 mm NaCl + 0 mg N kg^?1 sand + 10^?5 m GA₃, (vii) 100 mm NaCl + 40 mg N kg^?1 sand + 10^?5 m GA₃. Growth and physio‐biochemical attributes i.e. shoot length, leaf area, fresh weight, dry weight, net photosynthetic rate, stomatal conductance, malondialdehyde concentration, electrolyte leakage, total chlorophyll concentration, nitrate reductase and carbonic anhydrase activities, proline and glycinebetaine concentration, leaf – N, potassium (K) and sodium (Na) concentration and K/Na ratio were affected by NaCl treatment. But application of N or GA₃ alone as well as in combination proved beneficial in alleviating the adverse effects of salt stress on these growth and physio‐biochemical parameters. However, N applied with GA₃ proved more effective than N and GA₃ applied alone. The results revealed that combined application of N and GA₃ may ameliorate most of the attributes and prove to be a physiological remedy to increase the tolerance against the ill effects of salt stress in Brassica.     

30%矮•烯微乳剂对水稻茎秆理化特性的调控

寒倒伏是限制地水稻高产潜力充分发挥的因素之一。试验以垦稻12为材料,于水稻拔节初期叶面喷施30%矮·烯微乳剂,研究其对水稻茎秆形态建成、物质积累及产量构成因素的调控作用。结果表明,30%矮·烯微乳剂1.2 L hm^-2处理,能够显著缩短茎秆基部第1、第2节间的长度,增加基部节间粗度;显著缩小茎秆细胞宽度,增强细胞排列紧实度;改善茎秆的抗折性,茎秆弯曲折断强度和径向压缩强度比对照分别提高152.4%和82.5%;显著提高水稻齐穗期茎秆基部节间的碳氮比和灌浆后期茎秆中纤维素、半纤维素和木质素含量,显著降低处于固定伸长期的第2节间GA₃含量;改善水稻产量构成因素,提高了产量。综上所述,30%矮·烯微乳剂有利于提高水稻茎秆的抗倒伏能力,增加水稻产量。     

壮秆剂及用量对水稻产量和抗倒伏能力的影响

以籼粳杂交稻品种甬优2640、超级稻南粳9108为供试材料,设置壮秆剂A(壮秧剂∶速效硅∶生物炭=1.0∶0.5∶1.0)5个处理(A-1:18.75 kg hm~(–2)、A-2:37.5 kg hm~(–2)、A-3:56.25 kg hm~(–2)、A-4:75 kg hm~(–2)、A-5:93.75 kg hm~(–2)),壮秆剂B("杰伟"牌水稻生长调节剂)5个处理(B-1:7.5 kg hm~(–2)、B-2:15 kg hm~(–2)、B-3:22.5 kg hm~(–2)、B-4:30 kg hm~(–2)、B-5:37.5 kg hm~(–2))。在齐穗后30 d观测水稻基部第1节间(N1)、第2节间(N2)、第3节间(N3)、第4节间(N4)抗倒伏能力和主要物理性状,比较研究壮秆剂不同用量对水稻产量及抗倒伏能力的影响。两年试验结果表明,壮秆剂A对水稻产量及抗倒伏能力的影响要优于壮秆剂B,随着壮秆剂用量的增加水稻产量呈先增后减的趋势,其中A-3处理产量最高,其原因在于每穗粒数、结实率、千粒重均有所增加,壮秆剂B中B-3产量最高,壮秆剂A增产效果优于B的原因在于千粒重的增加。随着壮秆剂用量的增加,各节间倒伏指数呈现先减后增趋势,其中A-3、A-4处理的N_2、N_3倒伏指数显著小于对照。进一步分析壮秆剂A与B抗倒伏能力增强的原因在于抗折力的增加,壮秆剂A主要是通过增加N_1、N_2、N_3节间茎秆粗度、茎壁厚度和节间充实度增强了抗倒伏能力,壮秆剂B主要是增加N_1、N_2、N_3节间茎壁厚度来增强抗倒伏能力,两者比较壮秆剂A效果更明显。     

偏高秆偏大穗杂交粳稻屉优418和 辽优5218的抗倒伏能力分析

文章对偏高秆、偏大穗杂交粳稻屉优418、辽优5218组合在随机区组三次重复、较高肥力条件下的抗倒伏能力进行了分析。研究认为偏高秆、偏大穗杂交粳稻屉优418、辽优5218组合具有抗倒伏能力强的理想茎秆物理形状：地上部第一伸长节间长度很短，地上部第二伸长节间长度也较短，基部茎秆截面椭圆长轴、短轴长和面积大，壁厚宽和茎壁截面积大，植株表现出抗倒伏能力强；在育种和栽培实践中，通过减少第一和第二伸长节间长度，适当加强茎秆基部物理性状的强度，降低穗位，增加穗长和穗颈长度等，可以提高杂交粳稻植株的抗倒性，使倒伏与株高和生物产量的矛盾在更高产水平上得到统一     

Alleviation of drought stress in maize by exogenous application of gibberellic acid and cytokinin

The study was conducted to investigate the ameliorative roles of GA₃ and CK on adverse effects of drought in maize. Drought stressed maize plants were applied with GA₃ and CK at 50, 100, and 150 mg L^?l as foliar spray at the vegetative and the reproductive stages. Plant height, internode length, stem diameter, leaf chlorophyll index, and dry matter production were significantly affected by drought. In most cases, GA₃ and CK significantly improved the depressed plant traits, but in varying degrees depending on the growth stage encountering hormones, and their types and concentrations. Both GA₃ and CK were found to be very effective in alleviating drought-imposed adverse effects on maize at the vegetative phase. Such alleviating effects varied depending on the concentration of the hormones. Application of CK at 150 mg L^?l was excellent resulting in a 106% yield advantage compared to drought stress and 79.9% increase relative to well-watered controls. Conversely, GA₃ at 50 mg L^?l performed well showing 78.8% increase in grain yield. However, both GA₃ and CK had very little effect on improving the depressed growth and yield attributes in maize at the reproductive phase. The relative yield advantages for the hormones were mainly attributed to improving the cob and seed-bearing capacity of drought-stressed maize plants.     

Physiological Analysis of Growth, Yield Development and Grain Quality of Some Deep-water Rice (Oryza sativa L.) Cultivars

A field experiment was conducted with 10 deep‐water rice varieties (nine traditional and one improved), viz. Amona, Maguri, Rangoli, Kakua, Panikakua, Deoribao, Moimonsingia, Duatkalam, Dalbao and PJNB‐96‐10, to study their physiological performance, grain‐quality characters and yield. Among the cultivars, significant variations were recorded in plant height, root length, number of internode, tiller number, number of ear‐bearing tillers, panicle length, panicle weight, number of spikelets per panicle and filled grain percentage. The highest number of spikelets per panicle (199), filled grain percentage (95 %) and grain yield (4.32 t ha^?1) were recorded in Maguribao. The highest grain length was recorded in PNJB‐96‐10 (9.5 mm), whereas highest grain thickness was observed in Duatkalam (2.8 mm). Glutelin was the most dominant fraction of protein in all the tested cultivars. Maguribao showed the highest glutelin content (26.7 mg g^?1 dry weight), whereas Panikakua showed the highest amylose (24.45 %) and crude fat (4.64 %) content. Differences were also recorded among cultivars in fibre, ash and iron content in grain. Maguribao was found to have superior physiological traits for growth and hence may be considered for inclusion in deep‐water rice breeding programmes.     

Quantification of endogenous gibberellins in two flax (Linum usitatissimum L.) cultivars during seed development

Eight gibberellins (GAs) were identified and quantified in extracts of seed of the flax, Linum usitatissimum L. cv. Hwanamama, Hwabaekama by GC-MS-SIM and Kovats retention indices. Four of these gibberellins are members of the early-C13-hydroxylation pathway (GA₅₃, GA₁₉, GA₂₀, and GA₁), and four are members of the non-C13-hydroxylation pathway (GA₁₂, GA₂₄, GA₉, and GA₄). Of these eight gibberellins, GA₂₄ was more abundant in yellow-seeded flax (cv. Hwanamama) than in brown-seeded flax (cv. Hwabaekama), whereas GA₉ was 8.3-fold more abundant in brown-seeded flax (cv. Hwabaekama) than in yellow-seeded flax (cv. Hwanamama). In both flax cultivars, non-C13-hydroxylation pathway was the main route leading to endogenous accumulation of GA₄ in the seed.     

Effects of Night Temperature,Spikelet Position and Salicylic Acid on Yield and Yield‐Related Parameters of Rice (Oryza sativa L.) Plants

Periodic episodes of heat stress and seasonally high night temperatures (HNT) are predicted to occur more frequently in the current changing weather environment. These events affect aspects of crop growth and development, including oxidative‐stress damage, reducing crop yield and quality. Salicylic acid (SA), a naturally occurring phenolic compound, associated with thermo‐tolerance, prevents oxidative damage by detoxifying superoxide radicals and altering antioxidant capacity in plants. A study was conducted to determine the effects of HNT and SA on multiple rice yield‐determining parameters with special emphasis on effects of HNT and SA at different spikelet positions in the panicle. Plants were grown under ambient night temperature (27 °C) or HNT (32 °C) in the greenhouse. They were subjected to HNT through use of continuously controlled infrared heaters, starting from 2000 h to 0600 h. The HNT did not affect productive tillers, main‐stem panicle length or number of primary branches per panicle; however, reduced yield resulted from significant negative effects on spikelet fertility (SF), grain length and width. The grains located at the base of the panicle showed decreased fertility, length and width. Application of SA increased antioxidant capacity, thereby preventing damage to membranes, hence increasing yield by predominantly affecting SF in rice plants.     

利用“02428h”的eui基因选育长穗颈不育系

为研究隐性长穗颈水稻“02428h”的长穗颈基因eui在减轻不育系包颈度中的利用价值,以02428h为父本,培矮64S为母本和轮回亲本,经过连续3次回交将02428h的eui基因导入培矮64S,转育成了具有长穗颈基因的“P8hS”。与培矮64S相比,P8hS的株高增加35.6 cm,主要是穗颈节和倒2节间长度增加所致。eui基因的导入不仅可使培矮64S的穗包颈得到彻底改善,而且对培矮64S及其杂种的主要经济性状具有改进作用。     

Genome‐wide association analysis reveals flowering‐related genes regulating rachis length in rice

Rachis length is correlated with panicle size in rice. Unveiling the genetic basis of rachis length is important for understanding the genetic regulation of panicle size. In this study, we performed a genomewide association study of rachis length using 529 rice accessions from two environments. In total, 20 loci were identified for rachis length and distributed across the 12 chromosomes except for chromosomes 2 and 5. Thirteen of the 20 loci were not linked to the cloned panicle size genes. Six flowering‐related genes, including the CCT domain‐containing genes Ghd7, Ghd7.1, Hd1, OsCCT1 and OsCO3 as well as Ehd1, were associated with rachis length in this study. These findings suggest that the network of these flowering‐related genes probably participates in the regulation of rachis length and thus affects panicle length and yield. Interestingly, haplotype analysis showed that OsCCT1 is a putative candidate gene which plays a key role in the variation of rachis length. Together, the genetic loci identified in this study could be used for rice breeding by marker‐assisted selection to improve grain yield.     

不同穗型的3个粳稻品种的抗倒性研究

试验选用不同穗型的3个粳稻品种为材料,分析其抗倒机理及与倒伏密切相关的各性状,并初步探讨穗型与倒伏之间的关系。结果表明:株高与倒伏指数呈极显著正相关;节间长、茎粗、穗部性状等均与倒伏指数存在显著相关;直立、半直立穗型品种较弯曲穗型品种倒伏指数小,株高偏矮,基部茎杆节间短且粗壮坚韧,穗短而穂颈角小,表现出较好的抗倒性能。     

Ideotype design for lodging-resistant wheat

The plant characteristics required to make wheat lodging-proof for the least investment of biomass are calculated using a validated model of the lodging process and information about the dry matter costs of altering lodging-associated characters. The plant characteristics required to give a crop yielding 8 t ha⁻¹ with 500 shoots m⁻² and 200 plants m⁻², a lodging return period of 25 years include a height of 0.7 m, a root plate spread of 57 mm, and for the bottom internode a wall width of 0.65 mm with a diameter/material strength combination ranging from a diameter of 5.86 mm with a material strength of 20 MPa to a diameter of 4.00 mm with a material strength of 50 MPa. It is estimated that this ideotype would require 7.9 t ha⁻¹ of stem biomass and would have a harvest index of 0.42. Observations of a wide range of varieties grown using crop management to maximise lodging resistance without reducing yield potential showed that the root plate of the best variety was 7 mm less than the ideotype target, the stem character targets were achieved but not all in one variety, and the height target was achievable with the use of plant growth regulators. Plant breeders must therefore focus on selecting for a wider root plate and combining the appropriate stem strength characteristics.     

~(15)N示踪的水稻氮肥利用率细分

以粳稻武运粳23和超级杂交籼稻Y两优2号为供试品种,应用15N示踪方法研究不同时期施肥对水稻不同阶段氮肥利用率的影响,以确定不同时期施肥的最佳阶段氮肥利用率。结果表明,基肥在基肥阶段(移栽后的8 d左右)的吸收利用较低,2012年水稻基肥氮(15N)吸收量不到5 kg hm–2,2013年最大为7.5 kg hm–2,回收利用率在1.5%~11.5%之间;基肥主要是在蘖肥阶段(分蘖肥与穗肥之间)被吸收,其回收利用率在6.6%~24.9%之间,平均为15.6%;穗肥阶段(穗肥后到成熟)基本不再吸收基肥。基肥氮的总体恢复利用效率不高,在9.1%~22.8%之间,品种及氮肥运筹对基肥氮的总体恢复利用效率影响不显著。蘖肥主要在蘖肥阶段发生作用,施穗肥后水稻基本不再吸收蘖肥。蘖肥的总体恢复吸收利用率和基肥相当,在17%~34%之间,Y两优2号高于武运粳23。穗肥的回收效率最高,在54.0%~82.1%之间,武运粳23低于Y两优2号。水稻在整个生育期的总体氮肥恢复效率随氮肥用量的增加而下降,变化在32%~64%之间。水稻一生中吸收积累的氮素中,基肥的贡献占4.13%~10.59%(平均6.92%),蘖肥占3.98%~11.75%(平均7.58%),穗肥占13.32%~37.56%(平均26.02%),土壤的贡献在45.71%~70.83%(平均59.91%)之间。基蘖肥用量越大,其损失也越大,总体氮肥利用率也越低。研究结果证明,在水稻氮肥管理中必须考虑水稻各阶段对不同时期施肥的吸收利用情况,从而提高水稻氮肥利用效率,保证产量的同时减少不必要的损失。     

Indentification of true genetic dwarfing sources in foxtail millet (Setaria italica Beauv.)

Summary True genetic dwarfs hither-to not reported have been located in foxtail millet. The dwarfs as a group distinguished themselves from the talls in having altered constellation of characters. The morphological differences were highly significant for plant height, internodal length, and tillering potential. The talls had elongated internodes compared to dwarfs while there was no difference for node number on the main stem suggesting that short internodal length was primarily responsible for dwarfism. The dwarfs also showed slightly higher leaf number per plant, leaf area and harvest index compared to talls. The dwarfs were insensitive to exogenous GA₃ application indicating that GA₃ synthesis is not impaired. This suggests that dwarfing gene sources presently identified are true genetic dwarfs and their behaviour is similar to dwarfs derived from Norin 10 in wheat and Dee-geo-woo-gen in rice. The superior morphological frame makes these dwarfs ideal as far as plant type is concerned and offers immense potentialities in breeding high yielding foxtail millets.