Semi-dwarf Genotypes Research Articles

Energy Optimization in Different Production Technologies of Winter Triticale Grain

This article presents the results of a field experiment investigating the energy efficiency of grain produced by a semi-dwarf genotype of winter triticale at different levels of agricultural inputs. The energy efficiency of winter triticale grain production was evaluated in two low-input and two high-input cultivation practices that differed in the rate of nitrogen fertilizer (split application) and disease control. The energy inputs associated with the production of winter triticale grain at low levels of agricultural inputs were determined to be 14.5 to 14.7 GJ ha−1. Higher levels of agricultural inputs increased the demand for energy in grain production by 25% on average. The energy output of grain peaked (163.3 GJ ha−1) in response to a fertilizer rate of 120 kg ha−1 applied in a split ratio of 50:50 (BBCH 27/32) and two fungicide treatments (BBCH 31 and 39). The energy output of grain from the remaining cultivation regimes was 3–13% lower. The energy efficiency ratio was highest in the low-input cultivation regime with a nitrogen rate of 90 kg ha−1 split into two applications (60 and 30 kg ha−1 for BBCH 27 and 32, respectively), seed dressing with fungicide (thiram and tebuconazole) and one fungicide treatment (azoxystrobin) (BBCH 39).

Integrating marker-assisted selection and doubled haploidy for rapid introgression of semi-dwarfing and blast resistance genes into a Basmati rice variety ‘Ranbir Basmati’

Ranbir Basmati, an early maturing pure line selection of traditional Basmati 370, is widely cultivated Basmati variety in the Indian state of Jammu and Kashmir. The variety is tall statured, prone to lodging and highly susceptible to rice blast. The present study was carried out for genetic improvement of Ranbir Basmati for semi dwarf stature and resistance to blast by introgressing semi-dwarfing gene, sd1, and blast resistance gene, Pi9 from an improved Basmati rice variety, Pusa Basmati 1637 (PB 1637).The selfed progenies of two superior BC2F1 recombinants of the cross Ranbir Basmati/PB 1637 showing maximum recovery of recurrent parent genome and phenome were analyzed with gene-based markers to select plants homozygous for both Pi9 and sd1. These plants were processed via anther culture to produce homozygous doubled haploid (DH) lines. All the anther culture derived DH plants were short-statured compared to Ranbir Basmati and exhibited high level of resistance to blast. The analysis of yield and its component traits revealed the presence of superior transgressive segregants for various traits namely, effective tillers, grains per panicle and yield per plant. Combined use of marker-assisted selection and anther culture ensured speedy conversion of Ranbir Basmati into semi-dwarf genotypes with in-built resistance to rice blast. The study demonstrated the utility of anther culture as an adjunct to marker-assisted backcross breeding schemes for instant elimination of the residual background heterozygosity of the selected recombinants.

Stability and plasticity of grain weight per spike, 1000-kernel weight and yield of mid-high and semi-dwarf genotypes of winter bread wheat

Aim. To determine the stability and plasticity of the grain weight per spike, 1000-kernel weight and yield of mid-high and semi-dwarf winter bread wheat accessions. Results and Discussion. We determined the stability and plasticity of the grain weight per spike, 1000-kernel weight and yield of mid-high and semi-dwarf winter bread wheat accessions. The meteorological conditions during the vegetation periods in 2015-2018 made it possible to differentiate winter bread wheat accessions by stability and plasticity of the grain weight per spike, 1000-kernel weight and yield. The best winter bread wheat accessions of the NCPGRU’s collection, which were distinguished by grain weight per spike, 1000-kernel weight and yield, were evaluated for their stability degree (Sd) and plasticity level by regression coefficient. It was found that the proportion of accessions with high homeostaticity (bi <1) for the traits under investigation, which was most typical for mid-genotypes, was 70.6% for the yield, 64.7% for the 1000-kernel weight and 58.8% for the grain weight per spike, which is important for breeding for adaptability. Sources of high homeostaticity with a regression coefficient of <1 for the grain weight per spike (Zorepad Bilotserkovskyi, Anatoliia (UKR)); 1000-kernel weight (Krasa Laniv (UKR); Ilona (SVK)); yield (Pochaina, Krasa Laniv (UKR); Adel, Kazachka (RUS); OR2070011 (USA); Ilona (SVK), Darunok Podillia (UKR)) were singled out. In addition, we selected accessions with a wide environmental response (bi> 1), which can best fulfill their yield capacity under improved growing conditions or on an increased soil fertility, for the grain weight per spike (Zorepad Bilotserkovskiy, Anatoliia (UKR)); 1000-kernel weight (Harmonika, Prynada (UKR), Moskvich (RUS), Aran (AZE)); yield (Biloretskovskyi Zorepad, Prynada (UKR), Morozko, Vid (RUS)). Conclusions. The study of collection material of different eco- geographical origin enabled us to identify new sources of grain weight per spike, 1000-kernel weight and yield with increased environmental plasticity and stability, the use of which in breeding programs will contribute to the development of new highly productive and more valuable genotypes. Sources of high homeostaticity in winter bread wheat are valuable starting material to develop new highly adaptive varieties.

The Influence of Climatic Variations on the Stability of Wheat Plant Height

Abstract The decrease of variability sources and the genotypes instability as a result of climate changes from the last years were issues addressed in the breeding programs. For breeders the stability of some parameters like plant height is very important in selection process, therefore the influence of climatic variations it is aimed to be reduced by genetic response of the genotypes. Semi-dwarf genotypes are preferred by breeders because in this way is avoided the lodging risk. A set of 307 mutant and mutant/recombinant wheat DH lines, along with parental genotypes, was analyzed in three different years for plant height and the semi-dwarf selected lines were evaluated for stability of this parameter. The material was also analyzed for the presence of Lr34, or genes and 1A/1R translocation. In our study the reduced plant height and its stability was not associated with any of the genetic background

Morphological Variability of Colored Dry Bean (Phaseolus vulgaris L.) Germplasm From Artvin Province

In this study, 74 villages were selected and a total of 279 samples were taken from those villages according to the progressive sampling system. Regarding the seed size and color of the materials, 400 genotypes were grouped. These genotypes were sown in Samsun. Description of the genotypes was performed according to morphologic description criteria developed by IBPGR and EU-CPVO. A total of 68 observations were performed by adding some important agronomic traits. Description data for the rest colored genotypes were mentioned in the text. Of all colored seed producing genotypes, it was determined that 54 genotypes were dwarf, 15s genotypes were semi-dwarf and 78s genotypes were climbing. To determine the morphologic variability of local bean varieties of Artvin province, the collected material was divided into two groups as white and colored seeds. 145 white seeded and 147 colored seeded genotypes were subjected to Cluster analysis and dendogrames were formed. As a result of the cluster analysis it was established that bean genotypes having colored seed formed 26 subgroups. All the data obtained shows that this material has a rich variation and could be used for both new cultivars developing as dry and fresh consumption and different breeding purpose.

Analysis of early vigour in twenty modern cultivars of bread wheat (Triticum aestivum L.)

Fast development of seedling leaf area is a relevant trait in order to increase early resource acquisition. The use of semi-dwarf genotypes of wheat has decreased early vigour of modern cultivars. We studied early vigour of 20 cultivars cropped in Argentina, and our main objectives were: (i) to analyse the genotypic variability in early vigour; (ii) to study morphological traits that can be good indicators of early vigour, such as seed mass, leaf width, and specific leaf area; and (iii) to determine whether increased dry mass allocation to roots impacts negatively on early vigour. Experiments with non-size-selected and size-selected seeds were carried out in a greenhouse. A field trial was also conducted in order to test the reliability of the greenhouse results. Seeds mass was the main parameter related to early vigour. However, results from the experiment with seeds selected by size (45–50 mg seed–1) showed that seed mass per se only partially explains early vigour, since a significant coefficient of determination was observed between the seedling leaf area of each cultivar in both experiments (i.e. with randomly chosen or size-selected seeds). We observed a high coefficient of determination between net assimilation rate and changes in the ranking of early vigour of the cultivars with time after transplant. Root biomass was positively correlated with leaf area, indicating that the traits were not mutually exclusive. We built simple models by multiple regression to predict early vigour, including some parameters that were easy to measure. Seed mass and leaf width taken together showed better fit than seed mass or leaf width alone. We found a significant coefficient of determination between early vigour in greenhouse and field experiments; thus, screening for early vigour under semi-controlled conditions may be feasible.

The 1BL/1RS translocation decreases grain yield of spring wheat germplasm in low yield environments of north-eastern Australia

Wheat (Triticum aestivum L.) lines containing the 1BL/1RS chromosome translocation yield up to 20% more than established wheat cultivars in some Queensland environments. However, 1BL/1RS germplasm possesses a quality defect known as ‘sticky dough’, which is incompatible with the high-speed dough-mixing processes used for bread production in Australia. Therefore, we investigated whether the 1BL/1RS translocation conveyed a yield advantage to locally adapted germplasm across a wide range of environments that was sufficient to justify attempting to overcome the ‘sticky dough’ defect either through plant breeding or by altering the mixing processes. Three sets of recombinant inbred lines (RILs) that segregated for the presence or absence of the 1BL/1RS translocation were developed from crosses between 1BL/1RS germplasm (Seri and Genaro) and established local cultivars (Hartog and Banks), and grown in 11 environments representing six sites across southern Queensland and northern New South Wales and two years. The effect of the 1BL/1RS translocation on grain yield depended on environment and genetic background. In semi-dwarf genotypes of the Hartog/Seri and Hartog/Genaro crosses, the 1BL/1RS RILs had lower grain yield than the 1B RILs in the three lowest yielding environments. This effect was associated with changes in grain number per unit area, suggesting that the negative yield effect of the translocation is expressed before, or at, anthesis. In the higher yielding environments, the 1BL/1RS translocation conveyed a yield advantage in semi-dwarf genotypes of the Banks/Seri cross, but had no consistent effect on yield in semi-dwarf genotypes of the Hartog/Seri and Hartog/Genaro crosses. The 1BL/1RS translocation was also associated with decreased yield in the double-dwarf genotypes of the Hartog/Seri cross across all environments. We conclude that the 1BL/1RS translocation is not useful for local breeding programs, as it decreased yield among the more advanced, semi-dwarf germplasm in low-yielding environments that potentially represent up to 85% of the target population of environments, and had no consistent positive effect on yield in this germplasm in higher yielding environments.

Bean pod mottle virus Spread in Insect-Feeding-Resistant Soybean.

Bean pod mottle virus (BPMV) infection reduces yield and seed quality in soybean. To test the hypothesis that virus incidence and movement within plots would be reduced in soybean with resistance to feeding by the virus' bean leaf beetle (Cerotoma trifurcata) vector, BPMV spread was evaluated in five soybean genotypes at two inoculum levels over 2 years at two locations in Ohio. Soybean genotypes included two insect-feeding-susceptible genotypes (Williams 82 and Resnik), two insect-feeding-resistant, semidwarf genotypes (HC95-15 and HC95-24), and an insect-feeding-susceptible, semidwarf genotype (Troll). BPMV incidence was assessed in individual plants at growth stages R5/R6 and R7/R8 using enzyme-linked immunosorbent assay. Beetle feeding was visually assessed in 2004. Data for infection of individual plants were analyzed using a generalized linear mixed model, with a binomial distribution and logit-link. Within plots, BPMV incidence was highest in Resnik and Williams 82 and significantly lower in Troll. Incidence in HC95-15 was not significantly different than in Williams 82 and Resnik but incidence in HC95-24 was lower than in Resnik. BPMV incidence was also significantly (P < 0.05) affected by year, location, inoculum level and sampling date, with increasing incidence over time and higher incidence at the higher inoculum level. Beetle feeding damage was affected by the interaction of location-genotype. Significant spatial aggregation of infected plants was found for most plots but aggregation was independent of host genotype and inoculum level. Although the results indicate that BPMV infection varied by genotype, they do not support the hypothesis that insect-feeding resistance is sufficient to reduce the incidence and spread of BPMV.

Genetics of late maturity α-amylase in a doubled haploid wheat population

Late maturity α-amylase (LMA) in wheat is a defect where high-isoelectric point (pI) α-amylase accumulates in the ripening grain. Wheat genotypes vary in expression from zero to high levels of α-amylase, the latter with detrimental consequences on their use for value-added end products. Expression in each genotype is characterised by varying numbers of grains affected and different levels in each grain. Analysis of a doubled haploid (DH) population (188 lines) from WW1842 × Whistler has identified significant QTL on chromosomes 2DL, 3A, 3B, 3D, 4B, 4D, 5DS and 5BL. The 4B LMA allele (P &lt; 0.0001) from Whistler is closely linked to the QTL for the ‘tall’ allele (P &lt; 0.0001) of the Rht-B1 gene. The 4D LMA QTL (P &lt; 0.0001) in WW1842 co-locates with the QTL for the ‘tall’ allele (P &lt; 0.0001) of the Rht-D1 gene. This study has shown for the first time that a DH cross between two semi-dwarf cultivars with low or no LMA produces ~25% of progeny lines of the ‘tall’ genotypes with a high frequency of LMA. This is attributed to the large additive positive effects from the combination of one recessive ‘tall’ Rht-B1 gene and one recessive ‘tall’ Rht-D1 gene. High-yielding semi-dwarf genotypes with different combinations of Rht-B1 and Rht-D1 alleles which have very low or non-existent LMA expression (e.g. WW1842 and Whistler) may meet industry criteria for registration as commercial wheat varieties. However, when they are used as breeding lines, the cross produces some progeny genotypes with severe levels of LMA. These LMA genotypes comprise the gibberellic acid-sensitive ‘tall’ progenies and a very small proportion of semi-dwarfs. Thus, it is of paramount importance to screen the defect in wheat breeding programs. The suite of QTL identified for LMA will enable the use of marker assisted selection in the pyramiding of the beneficial QTL to maximise yield and minimise (or eliminate) LMA in semi-dwarf genotypes.

Efficiency of screening techniques for evaluating durum wheat genotypes under mild drought conditions

The main objective of this research was to evaluate fifteen durum wheat (Triticum durum) genotypes selected from joint project of Iran/ICARDA for drought tolerance using several indices. The trials were conducted under moderate levels of drought stress for three cropping seasons (20042006) in four locations in the highlands western of Iran. The combined ANOVA for grain yield over years and locations indicated significant differences among main effects (genotypes, years, locations) and their interactions. Principal component (PC) analysis based on the Spearman’s rank correlation matrix revealed that the screening methods were significantly inter-correlated with each other and can be classified into three groups; The first group included stress susceptible index (SSI), tolerance index (TOL) and yield stability index (YSI) where had significantly negative correlation with mean grain yield under supplemental irrigation condition and were able to identify drought resistant genotypes with low yielding performance. The second group reflects the drought tolerance indices including stress tolerance index (STI), geometric mean productivity (GMP), mean productivity (MP) and superiority index (Pi) which were appear to identify the high yielding semi-dwarf genotypes (G6, G4 and G3) with high drought tolerance. The parameters of relative adaptability to drought (bN), regression intercept (a) and regression coefficient (b) are in third group which were able to distinguish the genotypes G6, G5 and G10 with high adaptability and relative drought resistant. The final conclusion of this study is to reveal that not only genotypes but also screening methods can be classified into distinct groups considering different concepts of drought tolerance, resistance and susceptibility under mild drought stress.

ROOTING AND MULTIPLICATION ABILITY OF PERSIAN WALNUT AS INFLUENCED BY MOTHERSTOCK VIGOR AND PRECOCITY

Based on the frequent existence of precocious and dwarf walnut (J. regia L.) genotypes in Iran nurseries, different studies were conducted to collect and evaluate these valuable genotypes for various aspects, including consistency of growth under in vitro and in vivo conditions and impacts of seedling vigor on the walnut rooting and grafting. In the present study, the stability of seedling vigor under in vitro conditions and multiplication and rooting ability of the microcuttings were tested. To this, nodal explants of newly grown shoots derived from 5-year-old seedlings previously classified into three different clusters according to their vigor, were surface sterilized and cultured on DKW medium. The explants were subcultured monthly, up to 13 times, to increase the number of microcuttings. Results of the in vitro study showed that number of shoots derived from the dwarf and semi-dwarf genotypes was higher in comparison to the high vigor ones (3.3 vs. 2.3). The low vigor genotypes also showed shorter internodes, smaller shoot size (2.6 vs. 4.5 cm) and lower callus formation as well as higher rooting percentage (63.5% vs. 37.1%) and in vitro flowering. These results are consistent with the field observations, suggesting basitonic tendency, easy rooting and dwarf stability of low vigor genotypes under in vitro conditions. In conclusion, we suggest a simultaneous recurrent selection program for both dwarfing and rooting ability (selection of dwarf/semi-dwarf as well as easy-to-root clones) to utilize their advantages in a high-density orchard system.

Genetical and physiological studies of gibberellic acid insensitivity in semidwarf rye

Because of the breeding value of gibberellic acid (GA3) insensitive semidwarf genotypes in wheat, a screening for GA3 response within a collection of semidwarf ryes was initiated and up to now four genotypes (‘Moskowskij Karlik’, ‘Gülzow kurz’, ‘R18’, ‘Dwarf C) were found to be insensitive to applied gibberellic acid. In contrast to wheat, where all of the known alleles for GA insensitivity are (partially) dominant, the genetical studies did show that these four genotypes are carrying recessive alleles. Furthermore, it was found that the alleles of ‘Moskowskij Karlik’ and ‘R18 seem to have the same locus on chromosome 5R, whereas the GA insensitivity of ‘Gülzow kurz’ and ‘Dwarf C’ is governed by two alleles of a different locus on chromosome 7R. None of the identified alleles was located on chromosome 4R, which could have been expected from the homoeologous relationships to wheat chromosomes 4B and 4D, which are critical for GA insensitivity. Studies on endogenous levels of gibberellins are in accordance with the genetical results, and suggest the GA insensitivity in rye to be caused by a different mechanism, compared to wheat.

Dependence of Grain Weight of Spring Barley Genotypes on Traits of Individual Stems

The aim of the paper is to evaluate relationships between some plant traits and grain weight per spike of spring barley (Hordeum vulagre L.). Field trials were conducted in 1999, 2001, and 2002 in central Poland. Data were collected on morphological traits of individual plants of two cultivars, Rasbet and Rastik. The data were analyzed using path analysis. Causal relationships studied were similar for both cultivars: grain weight per spike was determined mainly by number of grains per spike (path coefficient was 0.723 for Rasbet and 0.700 for Rastik), whereas the effect of mean kernel weight was weaker (0.487 for Rasbet and 0.510 for Rastik). The only noticeable indirect effect was that of spike length on grain weight per spike via number of grains per spike (0.490 for Rasbet and 0.468 for Rastik); all the indirect effects of shoot length on grain weight per spike were negligible. We concluded that to develop new semi-dwarf and dwarf genotypes, emphasis should be placed on increased number of grains, kernel weight, and spike length.

The potential of semi-dwarf oilseed rape genotypes to reduce the risk of N leaching

SUMMARYIn northwest (NW) Europe, oilseed rape (OSR) is often used as a preceding crop for winter wheat. Due to its low N harvest index (HI) and to favourable soil conditions after harvest, large amounts of mineral N remain in the soil, which cannot completely be taken up by the subsequent wheat crop. This increases the risk of N leaching into the groundwater during the following winter. Recently, semi-dwarf genotypes of OSR were developed and made commercially available that show similar yields but reduced height growth compared to conventional genotypes. The present authors hypothesized that the introduction of dwarfing genes leads to an increase in HI for dry matter (DM) and for N of OSR. As a consequence, semi-dwarf genotypes would accumulate less aerial biomass, return fewer plant residues to the soil and need less N to achieve yield maximum compared to conventional hybrids or open pollinating varieties. This may lead to a reduced risk of N leaching after growing OSR. In order to test this hypothesis, field trials conducted in 2003/04–2005/06 near Kiel in NW Germany combined four commercial varieties of OSR (Express, Talent, Trabant and Belcanto as semi-dwarf genotype), two seeding dates (mid-August and beginning of September) and eight mineral N fertilization rates (0–240 kg N/ha). On average in 2003/04–2004/05, the semi-dwarf genotype Belcanto achieved significantly less seed yield (4·44 t/ha) than the other varieties (4·65–4·88 t/ha). However, all varieties tested required similar N fertilization to achieve maximum yield. In addition, N offtake by the seeds did not differ. No interaction between genotype and N treatment was observed. Detailed analysis of DM accumulation and N uptake during the growth period revealed only small differences between the varieties in the averages of all N treatments and both years. At harvest, Belcanto produced more pods/m2 and a slightly higher 1000 seed weight. Nevertheless, HI and N HI were similar for all genotypes. It is concluded that, despite its lower plant height, the semi-dwarf genotype did not provide the opportunity to reduce the risk of N leaching after growing OSR.

Screening for lodging resistance in spring wheat breeding programmes

AbstractSelection for lodging resistance in Canadian hard red spring wheat under natural conditions is difficult due to the sporadic and often random nature of lodging events. We conducted field trials in Edmonton AB Canada (2000–2002) to determine if either a high seeding rate, or artificially inducing lodging (by dragging a weighted apparatus across plots at the early milk stage), would be an effective screen for determining genetic lodging resistance in wheat breeding programmes. For the 25 genotypes tested, applying artificial lodging at the experimental mean early milk stage was a suitable method to screen and identify lodging tolerant and susceptible genotypes. Tolerance to artificially induced lodging was mainly found within semi‐dwarf genotypes, and susceptibility was mainly found within Canadian bread wheat genotypes. Severe lodging resulted in yield losses as high as 40%. Lodging tolerant genotypes identified in this study are now being crossed into elite western Canadian bread wheat in an effort to increase genetic lodging resistance within Canadian breeding lines.

Factors influencing composition and ruminal degradability of barley straw

Chemical composition and in situ ruminal degradability characteristics for 25 and 40 genotypes of barley straw were measured for crops grown in 1994 and 1995, respectively. Straw from semidwarf genotypes contained more crude protein and less neutral detergent fiber (NDF) than that from genotypes with medium straw length and effective ruminal degradability was 9% higher (P &lt; 0.01). Straw from two-row genotypes contained 19% more crude protein (4.4 vs. 3.7%) and 3% less NDF (75.2 vs. 77.6%) than that from six-row genotypes and effective ruminal degradability was 6% higher (P &lt; 0.01) when genotypes with medium-length straw only were considered. Genotypes with smooth awns had higher rates of degradation but contained less of the slowly degraded fraction than straw with rough awns when straws of medium straw length were compared (P &lt; 0.05). Straw from hulless genotypes contained more (P = 0.006) NDF than that from covered varieties. Both ambient and soil temperature were positively related (P &lt; 0.05) to effective ruminal degradability of straw, possibly because of associated greater leafiness when temperatures were higher and there was more light. It was concluded that it is possible to select barley genotypes that have superior straw nutritive value for ruminant animals. Key words: Barley, straw, degradability, cattle, genotype, environment

Correlations among the Yield and Yield Components at Segregating Populations Derived from Selection Based on Harvest Index in Bread Wheat

Fifteen populations were generated from a 6x6 diallel cross without reciprocal and the selection was applied based on harvest index in the F2 generation. The F2, F3, F4, F5 and F6 generations of the cross population were grown in a randomized complete block design with three replications at Bornova of Izmir province in Turkey. Correlation coefficients were estimated among the grain yield (g), plant height (cm), spike length (cm), 1000 kernel weight (g), biomass (g), harvest index (%), flag leaf width (cm), flag leaf length (cm) and number of spikes per square meter in almost all generations. It was found that there were significant positive correlations between the grain yield and the biomass production in all generations. The correlation between harvest index and grain yield varied at different generations. Harvest index had also significant positive correlations with thousand-kernel weight in the F2 and F3 generations. It was concluded that the grain yield could be increased with a higher level of total biomass in semidwarf genotypes and harvest index could be used for selection only if it has a high correlation and higher heritability than grain yield in further studies.

Natural outcrossing in common buckwheat

Common buckwheat is an obligate cross pollinating crop because of its sporophytic self-incompatibility system. Therefore a study to assess the extent of natural outcrossing was undertaken for two years at Morden and Portage la Prairie, Manitoba using the semi-dwarf character, which is due to a homozygous genotype with regard to a single recessive gene, as a marker. The semi-dwarf genotype was grown in 100 m rows running in four directions at 90 ° from a central 36 m2 plot of a normal, tall variety. At maturity, seed samples were taken from the semi-dwarf population at designated intervals. At least 200 F1 seeds from each sample were grown in the greenhouse to the 3-4 leaf stage and the proportion of tall plants was used to determine the percentage of outcrossing. Approximately 50% outcrossing occurred where the semi-dwarf plants were immediately next to the normal plants and then the proportion decreased with increasing distance. Although outcrossing occurred throughout the distance tested, there were no significant differences from 12 m onward from the pollen source. Lack of directional influence in outcrossing and a sharp reduction in the proportion of tall plants within a 3 m distance from the pollen source suggested that wind was not a major factor in dispersing the buckwheat pollen over long distances. Although a substantial cross pollination was limited to a few metres from the pollen source, nearly 1% outcrossing occurred even at 100 m. Since the distance in this experiment was limited to 100 m from the pollen source, the present results do not allow us to recommend the minimum isolation distance required to meet certain standards for buckwheat seed production.

Winter Rye Leaf Emergence and its Relationship to the Phyllochron

Winter rye (Secale cereale L.) is a high‐tillering cereal crop. Understanding the relationship between the phyllochron for mainstem leaves and that of tillers is useful in adequately describing plant development and selecting crop management strategies. This study was conducted to determine the phyllochrons of conventional height (CH) and semidwarf (SD) genotypes of winter rye and the relationship of the phyllochron of mainstem leaves to that of primary tillers. Three CH and two SD genotypes were planted in a controlled‐environment growth room. Leaf stages were determined with the Haun scale and the phyllochron calculated as the inverse of the slopes of linear regressions of Haun stage to growing degree‐days (GDD). For both CH and SD genotypes, the Haun stage increased linearly with GDD, and the phyllochron was constant in the pre‐vernalization (0 &lt; GDD ≤ 266) and vernalization (266 &lt; GDD ≤ 566) periods. During post‐ vernalization (566 &lt; GDD ≤ 914), the phyllochron for the mainstem increased with GDD. Leaves on the coleoptile tiller (TO), T1 (the tiller from leaf no. 1 of the mainstem), and T2 had mean phyllochrons similar to that for the mainstem. Leaves on higher positioned tillers (T4, T5) had greater phyllochron than the earlier tillers. The higher positioned tillers also required more thermal time units to emerge than the earlier tillers. To precisely describe winter rye development using the phyllochron, one should consider that the phyllochron changes with leaf and tiller position on the culm.

Effects of light, temperature, gibberellin (GA3) and their interaction on coleoptile and leaf elongation of tall, semi-dwarf and dwarf wheat

Near-isogenic wheat lines differing in height-reducing (Rht) alleles, in each of two cultivars, were used to investigate the effects of light intensity and of their interaction with temperature and GA3 application, on the elongation of the coleoptile and the first seedling leaf. Darkness caused a conspicuous increase in the lengths of the coleoptile and of the sheath and lamina of the first leaf, in GA3 treated and untreated seedlings of all genotypes grown at 11 and 25°C. The genotype effects and the effects of light intensity and GA3 application on leaf length were ascribed entirely to their effects on the rate of leaf elongation since the duration of leaf elongation was not affected by these factors. Temperature elevation from 11 to 25°C caused a 55% shortening of the duration of leaf elongation and a concomitant increase in elongation rate, which diminished with increased genotypic dwarfness. Accordingly, temperature elevation resulted in a significant reduction in leaf-length of the light-grown dwarf genotypes and the dark-grown dwarf and semi-dwarf genotypes. It is suggested that this temperature × light × genotype interaction effect is due to environmental dependent upper limits of elongation rate set by the Rht alleles.