Rachis Internode Research Articles

Genome analysis of Thinopyrum bessarabicum and T. elongatum

Thinopyrum bessarabicum (2n = 14; JJ) was successfully crossed with T. elongatum (2n = 14; EE) but the reciprocal cross failed. Five of the 19 F1 plants headed in a greenhouse without being vernalized. Spikes of F1 hybrids were intermediate to those of the parents for number of florets per spike, glume length, and the first rachis internode length, but similar to those of T. bessarabicum and T. elongatum for spike length and number of spikelets per spike, respectively. Karyotypes of mitotic chromosomes in the parental species revealed that three of the seven chromosomes in the J and E genomes were similar in length and arm ratio. Meiosis in the F1 hybrids substantiated the conclusion from karyotype analysis that the other four chromosomes had undergone some structural rearrangements such as reciprocal translocation. Metaphase-I cells in hybrid plants averaged 2.68 I, 4.68 II, 0.27 III, 0.27 IV, and 0.01 V. Although 10% of the pollen grains were stainable with I2–KI, F1 plants of T. bessarabicum × T. elongatum did not set seed upon selfing. It is concluded that the J and E genomes are so closely related that the E genome designation should be changed to Je. The evidence reported here supports the transfer of Lophopyrum elongatum to the genus Thinopyrum. Wheat breeders should be able to utilize the genes in T. bessarabicum as readily as those in T. elongatum.Key words: Genome, mitosis, meiosis, karyotype, idiogram, hybrid.

A New Species of Rhytachne (Poaceae: Andropogoneae) from Northern South America

Rhytachne gonzalezii is described and illustrated. It ranges from Apure, Venezuela to Para, Brazil. It is the third annual species known in this tropical African-American genus. Previously it had been confounded with the perennialR. rottboellioides from which it differs in its habit, branching culms, smaller sessile spikelets and rachis internodes, and awned upper glume.

Evaluation of Alien Chromosome Addition and Recombinant Isolines of Wheat1

Chromosome addition isolines (2n=44) and a recombinant isoline (2n=42) of common wheat (Triticum aestivum L.) were developed by selection of hemizygous or heterozygous plants having a blue aleurone (BA) gene from Elytrigia pontica (Podp.) Holub (syn. Agropyron elongatum (Host) P.B.) for 12 generations. This method of producing spontaneous interspecific chromosome recombination was simple to apply and had the advantage of simultaneously producing isolines. The BA isolines were compared to their nonblue aleurone (NBA) counterparts in field experiments. Protein and lysine percentage in the grain was enhanced by 15 to 20% in the 2n=44 BA addition lines, but no enhancement was found in the 2n=42 BA recombinant line. The enhanced protein in the addition lines was associated with lower fertility, grain yield, and kernel weight while these defects were not found in the BA recombinant line. Increased spikelet number, spike length, and rachis internode length, were expressed in BA recombinant and addition lines. Thus, those characters were intiuenced by the Elytrigia chromosome, but the enhanced protein effect was largely attributed to effects of aneuploidy. Reduced fertility in the BA addition isolines was believed to be the primary cause for lower grain yield and higher grain protein concentration than in NBA (2n=42) lines.

Melhoramento do trigo: V. Estimativas da herdabilidade e correlações entre altura, produção de grãos e outros caracteres agronômicos em trigo

Visando estimar a herdabilidade para várias características da planta do trigo (altura, produção de grãos, número de espigas por planta, de espiguetas por espiga, número de grãos por espiga e por espigueta, peso de cem grãos, comprimento da espiga e comprimento do internódio da raque), bem como as correlações entre elas, foram efetuados cruzamentos entre o cultivar IAC-5, de porte alto com 'Tordo', 'Vican-71' e 'Olesen', de plantas anãs, e com 'Siete Cerros', de porte semi-anão. Plantas representando os pais e as gerações F1 e F2 e os retrocruzamentos para ambos os pais foram estudadas em um ensaio em blocos ao acaso, com quatro repetições, na Estação Experimental de Itararé. Os dados de altura, produção de grãos e outros caracteres agronômicos foram obtidos na base de plantas individuais. Os cultivares escolhidos representaram um largo espectro de diversidade genética para altura das plantas, número de espiguetas por espiga, comprimento do internódio da raque e da espiga, número de espigas por planta e de grãos por espigueta e por espiga. A herdabilidade no sentido amplo para altura foi 0,8783, enquanto para número de espiguetas por espiga, comprimento do internódio da raque, número de grãos por espigueta e de espigas por planta, número de grãos por espiga e peso de cem grãos, os valores observados variaram de 0,3423 a 0,5073. As estimativas obtidas da herdabilidade no sentido amplo para produção de grãos e comprimento da espiga foram 0,2034 e 0,2963 respectivamente. Os valores da herdabilidade no sentido restrito para altura foram 0,8155 e 0,9290 dependendo do método empregado nas suas estimativas, e de 0,2232 a 0,3822 para os demais caracteres estudados; grande parte, porém, da variação genética total encontrada nas populações, para os diferentes caracteres em estudo, foi associada a uma ação aditiva de genes. Nas populações estudadas a característica porte alto foi correlacionada significativamente com maior produção de grãos por planta, de espigas por planta, de espiguetas por espiga, de grãos por espiga, grãos mais pesados e espigas mais longas. Nas populações F2 dos cruzamentos IAC-5 x Olesen e IAC-5 x Tordo, planta alta não se associou significativamente com maior número de grãos por espigueta, o mesmo se observando no F2 dos cruzamentos IAC-5 x Vican-71 e IAC-5 x Olesen para essa característica em relação ao maior comprimento do internódio da raque. Os resultados mostraram também que para a obtenção de plantas de porte médio com alto potencial de produção, qualquer uma das fontes de nanismo estudadas poderia ser utilizada, desde que grandes populações F2 fossem plantadas para assegurar maior freqüência de recombinantes desejáveis.

F1 monosomic of Triticum macha

By means of F1 monosomic analysis, genes governing several morphological traits were located in a strain of Triticum macha (2n=42). T. macha was crossed with all the 21 monosomic lines of PbC 591 (T. aestivum) and with a disome of PbC 591. Critical lines possessing the following recessive characters of T. macha were identified by comparing the monosomic F1's with the control cross. (1) The gene which controls compactness of the spike of T.macha is located on chromosome 6B. A gene symbol Cm is proposed for this character to distinguish it from C gene of T.compactum, which is located on 2D. (2) The glabrous nature of the outer glume is controlled by chromosomes 1A, 1B, 6B and 5D. (3) Genes on 6B, 3D and 5D govern the closed nature of spikelet at maturity. (4) The flat nature of the rachis internode of T.macha, in contrast to the swollen rachis of PbC 591, is under the control of chromosomes 2A, 1B, 6B and 6D. (5) Winter growth habit is controlled by genes on 5A, 2B, 6B and 5D; 5D being the most potent in inducing lateness.

Genetic Variation for Canopy Architecture and its Use in Wheat Breeding1

Genetic studies showed that two genes control the dense spike (short rachis internodes) of PI 190982 (Triticum aestivum L., sphaerococcum group), a tall wheat cultivar from Spain that has erect and short leaves. Few genes, most likely two or three, controlled most observed differences in flag leaf angle and length. Selection allowed the isolation of erect‐leaved types that yielded about 45% more grain than PI 190982 but about 20% less grain than standard cultivars. Erect and nonerect derived lines did not differ in yields between row spacings of 15 and 30 cm in field experiments in 2 years. PI 190982 appears to be a useful germplasm source for modifying canopy architecture, but the role of leaf erectness in reaching new high yield levels requires additional study.

Response of Barley Shoot Apices to Application of Gibberellic Acid and Abscisic Acid: Dependence on Tissue Sensitivity

Stimulation by gibberellic acid of rachis internode elongation in barley grown in short days was dependent on either the timing of application or on the amount applied in a dose at day 10. There was no immediate rachis internode elongation in response to gibberellic acid treatment until floret initials appeared and then only if sufficient gibberellic acid was present in the shoot apices of the barley plants grown in short days. Applications of gibberellic acid promoted the growth of the double-ridge meristem (upper ridge only) and this resulted in a group of abnormal spikelets being formed on the lower six nodes of the inflorescence, all of which were characterized by enhanced growth of the rachilla apical meristem. In a 2 × 2 factorial experiment with gibberellic acid, abscisic acid was found to slightly reduce the growth rate of the vegetative barley apex between days 10 and 14. Abrupt cessation of primordium formation, coincident with the appearance of stamen initials, was observed following continued application of both gibberellic acid and abscisic acid whereas neither hormone alone had this effect. Enhanced growth of the rachilla apical meristem of the basal six spikelets following application of gibberellic acid resulted in the formation of branched inflorescences, and this result was not altered by the addition of abscisic acid to the treatment.

On macroscopic traces of food plants in southwestern Asia (with some reference to pollen data)

By about 6000 B.C. a fairly large number of crop plants were already present: 3 wheat species, 3 barley species, 4 leguminous species, and linseed. For a reconstruction of the history of early agriculture in the Near East the botanical information is still insufficient. The origin of Triticum dicoccum has recently been questioned. The evidence from Çanyönü pleads in favour of the opinion that Triticum dicoccoides is the wild ancestor. The carbonized remains of free-threshing wheat constitutes a problem. Neither the grains nor the rachis internodes seem to provide clues for distinguishing between Triticum aestivum and Triticum durum . The evidence from Ramad suggests that linseed cultivation must have started in the second half of the seventh millennium B.C., if not earlier. Pollen analysis has already provided valuable information on prehistoric environments in southwestern Asia. In the Near East, the prospects to demonstrate palynologically the activity of Neolithic farmers seem to be less favourable than in Europe. In the pollen diagram prepared for a sediment core from Lake Beyşehir an early- historic land occupation phase could be demonstrated.

Characteristics and inheritance of radiation-induced mutations in barley II. Two short-awned mutations

Two mutations were obtained in a two-rowed, spring-type barley variety, Asahi No. 5. KM 114 was obtained in the X2 population of X-irradiated dormant seeds (15 Kr) and KM 218 was found in X2 of gamma-irradiated seeds (15 Kr). KM 114 had very short awns, short plant height, almost normal spike size, and narrow and thinner seeds with pointed tip. The mutant gene is Mendelian recessive. KM 218 plants were normal or slightly taller, had somewhat larger spike, with somewhat longer rachis internodes, medium-long awn, and slightly longer, narrower and thinner kernel than those of the parental variety. At maturity, grains are exposed in many seeds (semi-naked kernels). This mutant also has a conspicuous diagnostic trait; the abnormal development of rachilla into extra florets, some of which set seeds. This mutant gene is also Mendelian recessive. Genes for these two mutants are not allelic and are inherited independently as indicated in F2 and F3 analyses. Genes of these two mutations will serve as good marker genes in genetic and linkage studies in barley, because their character expression is consistent and the recessive homozygotes are viable and fertile.

Inflorescence development of semidwarf and standard height wheat cultivars in different photoperiod and nitrogen treatments

A comparative study was made of the growth and development of the shoot apex/inflorescence in two contrasting spring wheat (Triticum aestivum L.) cultivars: Marquis—a standard height, day-length-sensitive type; and Pitic 62—a semidwarf, Norin 10 derivative with relatively low day-length sensitivity. The effects of 8-, 12-, 16-, 20-, and 24-h photoperiods and of two nitrogen levels in 12 and 20 h on both cultivars were determined, as well as those of two phosphorus levels on Marquis in 20 h.Apical primordium production continued for a longer duration in Pitic than in Marquis, and the initiation of spikelet primordia was delayed. Spikelet development was more synchronous in Pitic than in Marquis in all treatments. Apical spikelet formation always coincided in both cultivars with the initiation of rachis internode extension. Inflorescence development after termination of spikelet primordia formation was as fast in Pitic as in Marquis (or faster in short photoperiods).In general, increasing N increased the rate and duration of primordium production (apical spikelet formation occurring later at high N), and delayed inflorescence development and extension. These effects were more pronounced in Pitic, resulting in much greater N responses for spikelet and grain numbers per spike, and for grain yields per spike. Effects of high P were similar to those of high N. Increasing photoperiod increased the rate, but decreased the duration of primordium production, and accelerated the development and the extension growth of the inflorescence.The results are discussed in relation to a postulated involvement of endogenous gibberellins and inhibitors in the regulation of inflorescence growth and development.

Inheritance of Sterile Brachytic in an Infraspecific Cross of Arachis hypogaea L.1

Twenty F2 progenies from reciprocal infraspecific crosses between Arachis hypogaea L. cultivars ‘Argentine’ and ‘Early Runner’ were grown in field plantings. At 4 to 8 weeks 10,167 seedlings (x̄ = 508/F1 plant) were classified for brachytic vs. normal growth. Brachytic plants have a reduced leaf rachis, shorter petioles, and stem internodes and are male and female sterile. F2 data tested by chi‐square were found to fit a phenotypic ratio of 243 normal:13 brachytic. All 29 possible chisquares were nonsignificant (P<0.05). No differences occurred between reciprocal crosses.Results indicate that the two parental cultivars differ at four unlinked loci, involving two sets of factors with cotnplementary‐duplicate action, to condition the brachytic character. Gene symbols Bs1, Bs2, Bs3, and Bs4 are proposed. Two dominant alleles, one at each of any two loci, will result in normal plants. Plants homozygous recessive at any three loci or at all four loci are brachytic. Normal is completely dominant.The efficacy of this gene model in interpreting results from investigations by previous researchers is shown by the lower chi‐squares and higher P‐values when their data are tested to the 243:13 ratio vs. the 15:1 ratio previously postulated.

NATURAL SELECTION IN A COMPOSITE CROSS OF BARLEY

A composite of 105 crosses involving 15 parental barley varieties was grown for 5 years at nine stations of widely different latitudes in Canada, U.S.A. and Norway. A resulting sample of seed was recovered from each station and grown with original seed in comparative studies at Edmonton. Significant differences were observed among plants from different stations for heading date, maturity period, yield, spike type, and awn type. Little difference was observed for plant height and seed size. There was little or no effect on collar type, neck shape, neck length, leaf width or shape of basal rachis internode. Natural selection acted strongly against black kernel, the elimination of which was probably due to genetic linkage with a character of low competitive capacity. In general, the shift in the gene pool was consistent with plant breeding objectives.

Effect of Soil Fertility and Plant Competition on Grain Sorghum Panicle Morphology and Panicle Weight Components1

AbstractPanicle weight components (i.e., number of branch whorls per panicle, number of branches per whorl, number of grains per branch and grain weight) and rachis morphology were analyzed under different soil fertility and plant population treatments.High soil fertility and low plant competition increased the 1000‐grain weight and number of grains per panicle. The latter component was affected by soil fertility through the number of branches per whorl and the number of grains per branch, and by plant competition through the number of whorls per panicle and the number of grains per branch. Higher soil fertility and lower plant competition promoted a longer panicle through the increase in rachis internode length and number of internodes, respectively. The degree of contribution of some components to the number of grains per panicle was not always equal throughout the length of the panicle.A negative correlation, which became stronger as the number of grains per panicle increased, was found between weight of grain and number of grains per branch. Intra‐panicle competition between these components was suggested.

Inheritance of Plant Height, Yield of Grain, and Other Plant and Seed Characteristics in A Cross of Hard Red Winter Wheat, Triticum aestivum L.1

The inheritance mechanisms of seven plant and seed characters were studied in the F1, backcrosses and segregating generations from the cross of two winter wheat varieties differing in plant height and other characteristics.Evidence for the control of plant height by three major gene pairs was obtained. Additive gene action accounted for most of the plant height variance. Maturity was controlled by a single dominant gene pair for earliness. A bimodal F2 frequency distribution for kernel weight indicated operation of a relatively few genes. Heterosis for high yield was evident. The 4380‐pounds‐per‐acre yield of the F1 exceeded the most productive parent by 12.9%. Heavy kernel weight and, to a lesser extent, number of spikes per plant contributed to the high yield of the F1. The genetic expression of spike length and number of rachis internodes was completely additive.Heritability percentages for plant height, spike length, maturity, and kernel weight were sufficiently high to indicate that selection in the F2 for these traits could be effective. Selection for number of rachis internodes, number of tillers, or grain yield would be ineffective. Plant height was significantly correlated with kernel weight, spike length, maturity, grain yield, number of spikes per plant, and number of rachis internodes.