Direct differentiation of ears and tassels from cultured shoot apices of maize

In vitro morphogenesis of inflorescences from the cultured corn seedling shoot tips was obtained on modified Murashige and Skoog (MS) medium in complete darkness. Some shoot tip meristems excised from seedlings of inbred line 515, inbred line 8112 and their filial generations would directly give rise to florets on modified MS medium supplemented with 2.0 mg/L N6-bezyladenine (6-BA) in five or six weeks. On the medium with 1.0 mg/L 6-BA and 0. 2 mg/L 2, 4-dichlorophenoxy acetic acid (2, 4-D), the explants swelled first, and produced multiple shoot clumps, then the culture of the shoot tips from all of the six inbred lines in experiment would ultimately initiate to develop ears and tassels accompanied by multiple shoot clumps developing on the medium with 1.0 mg/L 6-BA and 0. 2 mg/Lin-dole-3-butyric acid (IBA). The developmental patterns of the corn inflorescences were similar to the controls of normal plants in the field, but the number of the ears was much more than that of the tassels in vitro. It seem     

Development of the mixed inflorescence in Zea diploperennis litis, Doebley & Guzman (Poaceae)

Development of the mixed inflorescence in Zea diploperennis Iltis, Doebley & Guzman (Poaceae) Mixed inflorescences of diploperennial teosinte, which terminate the main branches of the plant, arise in the same fashion as tassel spikes. The apical meristem produces bracts in a decussate arrangement. A single axillary bud primordium is initiated in the axil of each bract. Growth of the bract is retarded as the bud enlarges and divides longitudinally into two separate spikelet primordia. The paired spikelets running in two ranks on either side of the inflorescence primordium produce the four-rowed condition typical of teosinte tasselS. In the transition region between male and female portions of the inflorescence, development of the pedicellate spikelet of each spikelet pair is arrested at an early ontogenetic stage. Continued growth of the sessile spikelet and associated rachis flaps destroy the remnants of the arrested spikelet in basal portions of the inflorescence. A similar abortion of the lower floret of the sessile spikelet results in a single pistillate floret per node at anthesis. These results provide further support for the hypothesis that a tassel-like mixed inflorescence of teosinte is ancestral to the maize ear.     

Growing degree days – Ecosystem indicator for changing diurnal temperatures and their impact on corn growth stages in Kansas

Understanding how climate change will affect plant phenology (shifts in the timing of plant activity) is central to many ecological and biogeochemical studies. This aspect of plant ecology often has been overlooked, but addressing the consequences of climate change for adaptive/mitigative management is now high on the list of priorities for funding agencies. This study is innovative because it uses growing degree days (GDD), which has existed since the 1730s, as an ecosystem indicator to study changing diurnal temperatures; their effects on different plant growth stages in the last century; and as a basis for development of future adaptive management strategies. Our results show the most recent time period (1980–2009) had the earliest emergence and the least variability among stations in the day at which the crop stage occurred for most stages except emergence and physiological maturity. 100 year linear trends in the stations indicated all seven crop stages except tassel initiation occurred earlier by one day per decade during the study period. The number of stations with significant decreases varied from 11 to 17 stations out of 23 stations in Kansas. Tassel initiation stage occurred later by one day per decade during the study period. The most recent time period (1980–2009) had the highest variability among stations and 30 year time periods. The variability in trends is higher in western Kansas when compared to eastern Kansas. This knowledge has transformative potential to improve our understanding of the occurrence and duration of the different plant growth stages, add local precision to earlier findings for changes in overall GDD that encompassed larger areas, and help explain the differences in trends from some earlier studies. These shifts in the phenology of agricultural plants as a result of climate change have implications on food production increases required to feed the growing population.     

两个相关基因表达量和SNP与玉米雄穗大小相关

玉米雄穗通常较发达,散粉量大于授粉需要,过量消耗能量会影响光合产物向果穗的分配,过于发达的雄穗还会影响群体透光性、降低光合效率。生产实践和育种研究证明,由于雄穗大小与玉米籽粒产量负相关,因此成为品种选育的间接选择指标。该研究根据前人的报道,从11个雄穗大小不同的玉米自交系中扩增角蛋白相关蛋白基因KAP5-4和受体样蛋白激酶基因CLV1的基因组序列,多重比较后用以分析其开放阅读框、保守结构和单核苷酸多态性,用荧光实时定量PCR检测其在雄穗原基中的差异表达,并与雄穗分枝数和雄穗干重两个度量雄穗小的指标进行了相关分析。结果表明:KAP5-4基因的相对表达量与雄穗分枝数(r=0.77,P0.01)和雄穗干重正相关(r=0.83,P0.01)。11个自交系的CLV1基因开放框在2 104 bp存在单核苷酸多态性,其中5个自交系的2 014~2 016 bp核苷酸组成密码子GAC,编码受体样蛋白第702位酸性的天冬氨酸,另6个自交系的2 014~2 016 bp核苷酸组成密码子AAC,编码受体样蛋白第702位极性天冬氨酰胺。在前5个自交系中,CLV1基因的相对表达量与雄穗分枝数(r=-0.92,P0.01)和雄穗干重(r=-0.91,P0.05)负相关;而在后6个自交系中,仅与雄穗干重负相关(r=-0.91,P0.05)。综上所述,KAP5-4和CLV1基因的表达和单核苷酸多态性与玉米雄穗大小关系密切,可开发功能性的DNA标记用于玉米育种的分子标记辅助选择。     

Morphological traits defining species differences in wild relatives of maize are controlled by multiple quantitative trait loci

We analyzed the genetic basis of morphological differences between two wild species of teosinte (Zea diploperennis and Z. mays ssp. parviglumis), which are relatives of maize. These two species differ in a number of taxonomically important traits including the structure of the tassel (male inflorescence), which is the focus of this report. To investigate the genetic inheritance of six tassel traits, quantitative trait locus (QTL) mapping with 95 RFLP markers was employed on a population of 425 F2 plants. Each trait was analyzed by interval mapping (IM) and composite interval mapping (CIM) to identify and characterize the QTL controlling the differences in tassel morphology. We detected two to eight QTL for each trait. In total, 30 QTL with IM and 33 QTL with CIM were found for tassel morphology. QTL for several of the traits mapped near each other, suggesting pleiotropy and/or linkage of QTL. The QTL showed small to moderate magnitudes of effect. No QTL of exceptionally large effect were found as seen under domestication and in the case of some other natural species. Thus, the model involving major QTL of large effect seems not to apply to the traits and species analyzed. A mixture of QTL with positive and negative allelic effects was found for most tassel traits and may suggest a history of periodic changes in the direction of selection during the divergence of Z. diploperennis and Z. mays ssp. parviglumis or fixation of QTL alleles by random genetic drift rather than selection.     

Environmental effects on the early stages of tassel morphogenesis in maize (Zea mays L.)

The effects of various environmental conditions on the initiation of tassel branches (NTB) and spikelet‐pairs (NSP) were examined in the stress‐sensitive maize inbred F53. Chilling induced the most important effect, with a dramatic decrease in both NTB and NSP, provided it was applied at the end of the vegetative phase and start of the floral transition phase. The primary cause of chilling‐induced abortion of the tassel branches could be oxidative stress in the leaves, since lowering light irradiance during chilling greatly reduced the effect of cold. The comparison of inbreds F53 and F2 revealed that both genotypes exhibited a similar period of cold sensitivity at the floral transition phase, although F2 was considered from field observations as a stress‐insensitive genotype (at least for tassel development). However, our results also showed a chilling acclimation response in inbred F2 but not in inbred F53. The similarities with the work by Lejeune & Bernier (1996 Plant, Cell and Environment 19, 217–224.) concerning the effect of chilling on ear initiation in the sensitive inbred, B22, are emphasized.     

控制玉米雄穗分枝数目和雄穗重的主效QTL的定位

利用2套具有共同亲本黄早四且分别含有230个及235个家系的F_2:3群体, 结合2年多点的表型鉴定, 运用完备复合区间作图方法对不同生态环境下(2007-北京、2008-北京、2007-河南、2008-河南、2007-新疆以及2008-新疆)的玉米雄穗分枝数和雄穗重进行QTL定位。同时, 利用基于混合线性模型的QTLNetwork-2.0软件进行基因×环境互作及上位性分析。6个环境下2个群体共检测到51个与雄穗分枝数和雄穗重相关的QTL(Q/H群体32个, Y/H群体19个), 其中包括7个主效QTL, 并在Q/H群体中确定了2个重要的QTL, 即位于7.01bin的Qqtpbn7-1和位于7.02bin的Qqtw7-2。对比2个群体的定位结果, 共挖掘到3个在不同遗传背景下的“一致性”QTL, 这些在不同环境及不同遗传背景下能够稳定存在的QTL可为玉米雄穗相关性状的生产应用以及精细定位提供有价值的参考。     

The sterols of normal and male-sterile maize tassels during development

The steroids of normal and male-sterile (Texas type) genotypes of maize were investigated during tassel development. A bioassay for estrogen activity of the normal meiotic and postmeiotic tassels was negative, indicating estrogen activity (estrone equivalent) much less than one ng/g of plant tissue. The sterols found were cholesterol, campesterol, stigmasterol, sitosterol, and probably isofucosterol, stigmast-7-enol, and 24-methylenecholesterol. In the premeiotic, meiotic, and postmeiotic stages of both genotypes between 300 and 400 μg of C₂₈ and C₂₉ free sterols per g tassels (wet wt) were found, the proportions of the sterols being ca 45% sitosterol, 30% stigmasterol, and 13% campesterol, with less than 5% each of the remaining sterols. In all three stages before saponification more free sterols were found in the normal than in the male-sterile tassels. The differences were significant at the 95% level in the meiotic and post-meiotic stages. The amounts of these sterols derived from esters decreased from approximately 140 μg/g in the premeiotic stage to 50 μg/g in the meiotic stage, and to an undetectable amount in the postmeiotic stage. After application of cholesterol-[4-¹⁴C] to the normal and male-sterile maize leaves for 3 days at meiosis, the label was found in the free sterols and steryl esters of the leaves but only in the free sterols of the tassels.     

控制玉米雄穗分枝数目和雄穗重的主效QTL的定位

利用2套具有共同亲本黄早四且分别含有230个及235个家系的F2：3群体,结合2年多点的表型鉴定,运用完备复合区间作图方法对不同生态环境下（2007-北京、2008-北京、2007-河南、2008-河南、2007-新疆以及2008-新疆）的玉米雄穗分枝数和雄穗重进行QTL定位。同时,利用基于混合线性模型的QTLNetwork-2.0软件进行基因×环境互作及上位性分析。6个环境下2个群体共检测到51个与雄穗分枝数和雄穗重相关的QTL（Q/H群体32个,Y/H群体19个）,其中包括7个主效QTL,并在Q/H群体中确定了2个重要的QTL,即位于7.01bin的Qqtpbn7-1和位于7.02bin的Qqtw7-2。对比2个群体的定位结果,共挖掘到3个在不同遗传背景下的＂一致性＂QTL,这些在不同环境及不同遗传背景下能够稳定存在的QTL可为玉米雄穗相关性状的生产应用以及精细定位提供有价值的参考。