Greater Leaf Area Duration Research Articles

Fungicide Spraying Programs Reducing Asian Soybean Rust Impact on Soybean Yield Components

Soybean is one of the leading agricultural commodities, and Brazil is currently the largest producer globally. Despite this, fungal diseases as Asian Soybean Rust (ASR) are among the primary limiters of high crop yields in Brazilian fields. Losses caused by the biotrophic fungus Phakopsora pachyrhizi can reach up to 90%, depending on weather conditions, and several components can be affected during soybean growth and reproduction. Here, we assessed fungicide spraying programs to ASR control, aiming to reduce the losses on soybean components. The experiments were performed under field conditions during the harvest season 2014/2015. The evaluated variables were soybean leaf area index, ASR severity, yield components, dry mass grain accumulation, protein, and oil content. The yield components assessed were the number of pods per plant, seeds per pod, seeds per plant, and thousand-grain weight. The disease severity gradient was generated using seven fungicide spraying programs, differing in time, number, and type of fungicides. Three fungicide programs that included applications in the soybean vegetative and reproductive stages were more efficient. These programs resulted in the lower area under the disease progress curve (AUDPC), greater leaf area duration (LAD), and health leaf area duration (HAD) than the untreated soybean. The ASR infection in soybean resulted in reduced LAD and HAD, and as a consequence, interfered negatively with dry matter accumulation, yield components, and grain yield.

Morphological and physiological traits of large-panicle rice varieties with high filled-grain percentage

Understanding the morphological and physiological traits associated with improved filling efficiency in large-panicle rice varieties is critical to devise strategies for breeding programs and cultivation management practices. Information on such traits, however, remains limited. Two large-panicle varieties with high filled-grain percentage (HF) and two check large-panicle varieties with low filled-grain percentage (LF) were field-grown in 2012 and 2013. The number of spikelets per panicle of HF and LF both exceeded 300, and the filled-grain percentage (%) of HF was approximately 90, while that of LF was approximately 75 over the two years. The results showed that when the values were averaged across two years, HF yielded 12.9 t ha−1, while LF yielded 11.0 t ha−1. HF had a greater leaf area duration, biomass accumulation and transport of carbohydrates stored in the culm to the grains from heading to maturity compared with LF. HF exhibited a higher leaf photosynthetic rate, more green leaves on the culm, and higher root activity during filling phase, especially during the middle and late filling phases, in relative to LF. The length of HF for upper three leaves was significantly higher than that of LF, while the angle of upper three leaves on the main culm was less in both years. Meanwhile, specific leaf weight of HF was significantly higher when compared with LF. In addition, the grain filling characteristics of HF and LF were investigated in our study. Our results suggested that a higher leaf photosynthetic rate and root activity during filling phase, greater biomass accumulation and assimilate transport after heading, and longer, thicker and more erect upper three leaves were important morphological and physiological traits of HF, and these traits could be considered as selection criterion to develop large-panicle varieties with high filled-grain percentage.

Primary Growth Parameters of Three Alfalfa Cultivars Adapted to Highland Climatic Conditions

AbstractAn irrigated field study was conducted to determine the relative importance and inter‐relationships of growth parameters of three dormant alfalfa (Medicago sativa L.) cultivars grown in the highlands of Eastern Anatolia, Turkey, in 2000–2003. The fast‐growing cultivar Savas had the greatest dry matter (DM) yield at the final sampling date with the greatest mean crop growth rate. In addition to a greater relative growth rate (RGR), this cultivar had more stem branching and greater leaf area in the canopy, which resulted in greater leaf area index (LAI) and greater leaf area duration. Despite the considerable increase in leaf area ratio (LAR: leaf area per unit shoot DM), the reduction in RGR of all cultivars over time was the result of a large decline in net assimilation rate (NAR) due to increasing specific leaf area (SLA). Intracultivar variation in the RGR of alfalfa is mainly determined by NAR and SLA, and both were significantly higher for Savas than the other two cultivars. The relative importance of NAR and SLA to RGR changed due to increasing self‐shading as the LAI of the canopy increased, creating a trade‐off between NAR and SLA.

Effects of mulching materials on the growth, development and yield of white yam

Two similar experiments are described in which the effects of different mulching material and staking on the growth, development and yield of white yam ( Dioscorea rotundata ) Minisetts were studied. One white yam cultivar TDR 131 was used and the treatments were: black and white embossed polyethylene plastic (Visqeen 38 mu) with either black or white surface up; light weight black polyethylene plastic, rise straw; staking but no mulch, and no staking and no mulch. Each experiment was laid out in a randomized complete block design with four replications. Polyethylene plastic mulch with white surface up was superior to all other treatments. Total dry matter per plant and total fresh tuber yield were all consistently higher in plants grown under the white surface polyethylene plastic mulch. in 1985, mean tuber size was more than 34% larger than in the traditional staking system and nearly double the value obtained with no staking no mulch treatment. In 1986, mean tuber size was again larger with white surface plastic mulch but not significantly different from those of the staking and rice straw treatments. Plants in all treatments attained peak leaf area index (LAI) about 100 days after planting and those in the white surface plastic mulch maintained a higher LAI for most of the growing season. White surface polyethylene plastic mulch gave the larger Leaf Area Index and Greater Leaf Area Duration which ensure a high bulking rate over a comparatively longer period. It is suggested that under tropical conditions, farmers would obtain better seed yam yields through the use of white surface polyethylene plastic mulch.

EFFECT OF ALTERING PLANT DENSITY ON GROWTH CHARACTERISTICS OF SUMMER RAPE

The effect of 15- and 30-cm row spacings and 1.5, 3.0, 6.0 and 12.0 kg ha−1 seeding rates on growth characteristics, as measured by growth analysis, of summer rape (Brassica napus L.) was studied under southern Manitoba growing conditions. Growing degree days (GDD) was used in the growth analysis formulae as a measurement of time. Over all seeding rates, summer rape grown in rows spaced 15 cm apart produced more dry weight (W), a greater leaf area index (LAI) and a greater leaf area duration (LAD) than when grown in rows spaced 30 cm apart. The 15-cm row spacing treatments had a higher crop growth rate (CGR) and a greater net assimilation rate (NAR) than the 30-cm row spacing treatments. Summer rape grown at seeding rates of 6.0 and 12.0 kg ha−1 had a greater W, LAI and LAD during vegetative development than summer rape grown at seeding rates of 1.5 and 3.0 kg ha−1. This was primarily due to increased plant density. After flowering there were no differences for W, LAI and LAD attributable to differences in seeding rates. Summer rape grown at seeding rates of 6.0 and 12.0 kg ha−1 had a lower CGR and NAR during flowering than that grown at 1.5 and 3.0 kg ha−1 seeding rates indicating that plants produced from lower seeding rates were more photosynthetically efficient than plants produced from higher seeding rates.Key words: Brassica napus, growth analysis, row spacing, seeding rates, rape (summer)

Effect of different inter-row spacings on faba beans of different form

Plants with different morphologies may exploit the space available to them more or less effectively. Differences in inter-plant competition were examined in a field trial with determinate and semi-determinate varieties of faba bean ( Vicia faba L.; cv.'s Ticol and Alfred, respectively) grown at three different inter-row widths. Plant mortality was greater in Alfred than in Ticol and especially at the widest inter-row spacings (47.6 cm). The smaller size of the determinate forms and their ability to branch may enable them to more effectively exploit the aerial environment, particularly at wider inter-row spacings. Alfred yielded more than Ticol, which was attributed to both a greater leaf-area duration and a greater ability to transfer assimilates from the stem to the pods during grain growth. Different inter-row widths had no effect on yield, although the numbers of stems, pod-bearing nodes, pods and seeds per unit area were reduced by wide inter-row spacings. The practical signficances of this in terms of weed control and intercropping is discussed.

Growth analysis of spring-type oilseed rape

Abstract A quantitative analysis of growth, development and yield of eight genotypes of Brassica napus L. and two genotypes of B. campestris L. were conducted in 1980 field experiments in central Alberta. B. campestris L. reached all growth stages, except onset of stem elongation, earlier than B. napus L. and correspondingly had a shorter stem elongation period and seed formation period. B. campestris L. had higher leaf emergence rates during all growth periods. B. napus L. had greater crop dry weight at first flower and fifteen days after first flower and greater mean crop growth rate from seeding to first flower. Mean relative growth rates were higher in B. napus L. than B. campestris L. during all growth periods. B. napus L. had greater leaf area index at first flower and fifteen days after first flower, greater axillary branch leaf area index at first flower, greater leaf area duration from first flower to maturity of first pod, and greater axillary branch leaf area duration from first flower to maturity of first pod,than B. campestris L. Late maturing genotypes of B. napus L. had higher leaf emergence rates during all growth periods than did the earlier maturing genotypes, but were later in reaching first axillary branch leaf, first flower, first true leaf senesced and end of true leaves. This study confirmed other studies which indicated ‘number of days to first flower’ as a major factor in determining the time to maturity in both annual rapeseed species. Earlier maturing genotypes of B. napus L. had greater mean leaf area ratios from seeding to first flower, axillary branch leaf area duration, and mean relative growth rates over all growth periods. Late maturing genotypes had greater mean unit leaf rate from seeding to first flower, crop dry weight at first flower and fifteen days after first flower, mean crop growth rates over all growth periods and greater leaf area index at first flower and fifteen days after first flower. The greater axillary branch leaf area duration of earlier maturing genotypes of B. napus L. is advantageous since it coincides with seed filling. The usefulness of mean relative growth rate as a selection tool in breeding programs warrants further study. Given the greater efficiency of earlier maturing genotypes, they could be more productive at higher seeding rates than genotypes which are not as efficient.

The effect of reduced branching on yield and water use of chickpea (Cicer arietinum L.) in a Mediterranean type environment

An earlier study indicated that seed yield in chickpea was limited by the low harvest index of later-formed basal branches and that eliminating these by restricting branching to no more than two per plant, each with a high harvest index, should result in higher seed yields. This was tested in a dry Mediterranean type environment at Merredin in the south western Australian cereal belt by debranching high density stands of chickpea (70 plants m−2), leaving only the main stem and first basal branch, and comparing them with freely branching controls. Eliminating less productive, later basal branches had virtually no effect on above-ground biological yield (approx. 650 g m−2) but increased the harvest index by 31% and seed yield from 1.35 to 1.87 t ha− (P < 0.01). Dry matter ot tops, produced after flowering in the debranched crop, exceeded the control by 39 g m−2 and this was associated with an increased in apical (fruiting) branches of 110% in the main stem and 183% in the first basal branch. The debranched crop produced 73% more pods than the control, due to more flowers (2800 v. 2263 m−2) and increased pod set (61 v. 44%). Increased efficiency of podding in the debranched crop was compensated, to a small extent, by decreases in seeds per pod and mean seed weight relative to the control. Maximum leaf area index of 2.6 was similar for both treatments but took 14 days longer to attain in the debranched treatment, thus increasing leaf area duration (LAD) during seed filling. In the debranched crop, slower canopy development was associated with lower water use (122 mm v. 137 mm) orior to flowering, and with greater LAD and increased water use (76 mm v. 61 mm) after flowering. Total water-use was about the same at 198 mm. Leaf water potentials were consistently higher in the debranched plants throughout the season, reaching −2.6 MPa (0.6 MPa higher than controls) at 119 days, 30 days after 50% flowering. The debranched crop produced 9.5 v. 6.8 kg seed ha−1 mm−1 of total water used. Results are discussed in relation to application of the ideotype approach to yield improvement, noting that selection from stands at conventional low plant densities may fail to detect higher yielding, less competitive (communal) plant types.

Comparative Growth Analysis of Two Spring Wheats and One Spring Barley1

Two cultivars of spring wheat, Triticum aestivum L., cvs. ‘Neepawa’ and ‘Pitic 62’, and one cultivar of spring barley, Hordeum vulgare L., cv. ‘Bonanza’, were compared for grain yield and its relationship to patterns of leaf area development and dry matter accumulation. Each cultivar was planted at an early and a late seeding date at Saskatoon in 1980 and in 1981. Leaf area (cm2/plant) and biological yield (g/m2) were determined at weekly intervals commencing five weeks after seeding. Grain yield, components of grain yield, and final biological yield were measured at maturity. Grain yield was found to be a curvilinear function of final biological yield in Pitic 62 and Bonanza but the relationship appeared to be linear for Neepawa. Within a cultivar, higher biological yield gave higher grain yield.Bonanza barley produced more dry matter and greater leaf area than either wheat cultivar early in the season. This advantage disappeared as the crop approached maturity. Pitic 62, although having greater maximum leaf area index and greater leaf area duration than Neepawa, tended to have a similar pattern of dry matter accumulation early in the season. Pitic 62 had greater final biological yield and grain yield by virtue of its later maturity. Yield of wheat might be increased without delaying maturity by searching for types which grow quickly under cool spring conditions.

Shading Responses of Purple and Yellow Nutsedges (Cyperus rotundusandC. esculentus)

The effects of shade on dry-matter production, leaf area, and biomass partitioning in purple nutsedge (Cyperus rotundusL.) and yellow nutsedge (C. esculentusL.) were determined in a controlled-environment greenhouse with a day/night temperature regime of 32/26 C. For comparison with a full-light treatment, screening provided 40, 70, and 85% shade. Shading significantly reduced height of yellow nutsedge and dry-matter production, leaf-area production, and rhizome and tuber formation of both species. Shading decreased the partitioning of plant biomass into tubers and rhizomes and increased partitioning into leaves. Yellow nutsedge had a higher net-assimilation rate than purple nutsedge at all levels of shading, but the greater leaf-area duration or total amount of leaf area present in purple nutsedge resulted in greater dry-matter production by that species. The responses of the two species showed no differences in shade tolerance.