Changes In Number Of Grains Research Articles

Grain yield responses to planting density in twin and narrow row cultivation of early cultivars in maize

AbstractWe investigated how the responses of grain yield of maize to planting density depended on planting pattern (twin row, TR; narrow row, NR; narrow twin row, NTR; compared with conventional row (CR) cultivation) over 2 years using cultivars with relative maturity of 93 days. Grain yields were higher in order of NTR ≥ TR ≥ NR ≥ CR in all planting densities. Changes in grain yield and total dry matter yield with planting density followed significant negative quadratic regression curves in all planting patterns, increased with dense planting from 9.7 to 10.4 planting density and decreased thereafter. Changes in number of grains per ear and hundred grain weight with planting density followed significant negative linear regression in all planting pattern, and number of grain per ear, hundred grain weight and harvest index decreased with dense planting. The quadratic coefficient of the quadratic regression model, which indicates the changeability of the planting density response of grain yield, was lowest for NTR, followed by TR, NR and CR. The decline in number of grains per ear in response to increasing planting density for different planting patterns was NTR ≤ TR ≤ NR ≤ CR. The planting density response of total dry matter yield closely follows that of the grain yield in all planting pattern. But decrease in harvest index due to increased planting density for different planting patterns was lowest for NTR, followed by TR, NR and CR. Considering the relationship of grain yield to their related traits, the improved stability of grain yield for the specific planting patterns from the fact that the decline in number of grains per ear for different planting patterns is NTR < TR ≤ NR < CR. The specific planting patterns moderate the decline in harvest index and number of grains per ear with increasing planting density by enabling the maintenance of greater inter‐individual distance a given planting density.

Morphological characters, plant phenology and yield of spring barley (Hordeum sativum L.) depending on cultivar properties and sowing date

During the period 2008-2010, microplot experiments on spring barley were carried out in the experimental field of the Institute of Soil Science and Plant Cultivation – State Research Institute in Puławy, on a good wheat soil complex. The following cultivars were compared: ‘Conchita’, ‘Kormoran’, ‘Rufus’, ‘Skald’, ‘Skarb’ (2008-2009) as well as ‘Afrodite’, ‘Aliciana’, ‘Bordo’, ‘Skald’, and ‘Suweren’ (2009-2010), in terms of their morphological characters determining grain yield and their response to sowing date: 7-12 April and 17-22 April. Among the spring barley cultivars tested, there were large differences in productive tillering of plants, number of ears per unit area, and grain yield. Smaller differences related to number of grains per ear and 1000 grain weight. The cultivars ‘Suweren’ and ‘Skarb’ were characterized by high grain yield thanks to greater plant tillering and higher number of ears. The cultivar ‘Bordo’ was marked by the highest number of grains per ear, while cv. ‘Kormoran’ had the highest 1000 grain weight. A delayed sowing date caused a shortening of the growing season by 8-9 days and a shortening of all plant growth stages. This negatively affected number of ears per unit area and grain yield, but did not result in significant changes in number of grains per ear and 1000 grain weight. ‘Suweren’ and ‘Skarb’, i.e. cultivars with higher tillering ability, can be considered to be cultivars more tolerant to delayed sowing date.

Yield stability and development in two- and six-rowed winter barleys under Mediterranean conditions

Under the irregular weather that characterises Mediterranean environments, to increase yield stability in cereal crops represents an important objective for agricultural progress. In this study, a series of field experiments were conducted with two- and six-rowed barley cultivars under Mediterranean conditions (southern Spain) to determine their differences in yield stability and to identify the influence that initiation and mortality of both the spikelet and tiller could exert on yield differences. Yield stability differed markedly in two- and six-rowed cultivars. The yield of two-rowed cultivars was more responsive to environmental changes than that of the six-rowed cultivars, which consistently showed more stable behaviour, outyielding the two-rowed barleys in the lowest yielding environments. Two-rowed cultivars had far more spikes per m 2 than did six-rowed cultivars, while the latter consistently had more grains per spike, with a lower average grain weight. Yield differences among environments, for both groups of cultivars, were more associated with changes in number of grains per unit of land area than to differences in individual grain weight. Six-rowed cultivars, as expected, produced virtually threefold more spikelets per spike than the two-rowed cultivars. Although there was a large difference between two- and six-rowed cultivars in spikelet abortion, the proportion of abortion was fairly stable across environments. Two-rowed cultivars consistently tillered at a higher rate (0.11 tillers per day) than the six-rowed barleys (0.07 tillers per day), though the magnitude of the difference in tillering was more affected by the environment than was the difference in spikelet initiation. Under Mediterranean conditions the constitutive capacity of six-rowed cultivars to have a reduced tillering rate, even under favourable growing conditions, as compared with that of two-rowed cultivars could be a useful strategy to save resources that may be more efficiently used during the critical phases for yield determination. This explains their higher yield stability when compared with two-rowed cultivars.

Wheat Development as Affected by Radiation at Two Temperatures

A wheat cultivar (Condor) was grown in two experiments (thermal regimes 18/13 and 21/16°C) under low (298 μE m-2: s-1) radiation regimes during either an early phase from seedling emergence to terminal spikelet initiation (S2), a late phase from terminal spikelet initiation to anthesis (S2), or for the full period from seedling emergence to anthesis (S12), or high (560 μE m-2s-1) radiation throughout the growing period (S12) to determine whether developmental events are affected by radiation. The main developmental events considered in this study were the timing of terminal spikelet initiation and anthesis, the final number of leaf and spikelet primordia initiated in the apex and the rate of leaf appearance. Number of grains per spike and culm height were also measured. The duration of each phenophase was not affected by radiation intensity. Temperature affected the rate of wheat development, but the acceleration of development due to temperature during the seedling emergence - terminal spikelet initiation phase only slightly reduced (from 24.8 to 23.2 days). Differences in time from terminal spikelet initiation to anthesis were greater than in the earlier phases, having been the duration reduced from 24.6 to 20.0 days due to high temperature. Associated with the lack of effect of radiation on phasic development and the negligible effect of temperature on the duration of the early phases of development, final Leaf number was practically unchanged in this study by either the radiation level or the growing temperature. Thus, radiation did not affect the rate of leaf initiation. The number of spikelets was affected by neither the treatments nor the thermal environment. The rates of leaf appearance were accelerated by temperature. Radiation, on the other hand, did not significantly alter the rates of leaf appearance in any of the treatments. As expected from many sources in the literature, the number of grains per spike was significantly affected by radiation during the phase from terminal spikelet initiation to anthesis. Due to the lack of significant effects of radiation on the developmental patterns of wheat, the changes in number of grains per spike were due to changes in the number of grains born in each spikelet. The results of the present study were compared with others available in the literature on the effects (or lack of them) of radiation and CO2 concentration on phasic development, plastochron and phyllochron in wheat to reach the general conclusion that the rate of developmental events in wheat, in contrast to other plants, is almost completely independent of the availability of assimilates, with a possible exception for the Equatorial latitudes.

Changes in physiological attributes of the dry matter economy of bread wheat (Triticum aestivum) through genetic improvement of grain yield potential at different regions of the world

The understanding of the changes produced by plant breeding on wheat grain yield and on its determinants, through the study of the behaviour of cultivars released at different times during the breeding process, could be a useful tool to define future selection criteria. The aim of this paper was to examine the genetic improvement effects on bread wheat grain yield potential and on its major physiological determinants in different countries. Generally, it seems that the genetic improvement produced important increases in harvest index, but it did not produce important changes in total biomass. The genetic gain in grain yield ranged from 0.58 g m-2 year-1 (India) to 5.84 g m-2 year-1 (Mexico); reflecting important differences among genetic improvement programmes. However, when the comparisons were made in relative values, the difference was much lower, ranging from 0.16% year-1 to 0.90% year-1, for the previously mentioned countries, respectively. Most of the regions showed relative genetic gains of around 0.45% year-1. Similar patterns of relative genetic gains in harvest index were found. Half of the total gain in grain yield in the past was due to genetic gain in grain yield potential. However, it is expected for the future, that further increases in grain yield will rely more on genetic gain than on technologic gain. Thus, a discussion about possible strategies in future breeding programmes of bread wheat is attempted throughout the paper. The changes in grain yield were mostly associated with changes in number of grains per m2 rather than with changes in individual grain weight. It appears that the source: sink ratio during the grain-filling period was very high in old cultivars, whereas the source: sink ratio in modern cultivars is more balanced. Further increases in number of grains m-2 could be compensated by a reduction in individual grain weight, if simultaneous improvement in source strength during grain-filling is not achieved. The crop attributes which have been changed together with the mentioned traits are discussed and alternative selection criteria are suggested.

The differential response of barley genotypes to nitrogen application in a Mediterranean-type climate

The response of 12 barley cultivars to nine levels of nitrogen was studied in the field at Adelaide, S.A. The cultivars were selected from a world collection according to origin, number of spikelet rows and maturity, and their response was measured in terms of yield components, harvest index and straw and grain yield. The optimum nitrogen level for grain production differed greatly between cultivars, some giving a maximum yield at 0 kg N/ha, others showing a typical parabolic response, and others giving increasing yields up to 275 kg N/ha. Although grain yields by cultivars at their optimal level differed the highest-yielding cultivars with optima at 0,70 and 275 kg N/ha had similar yields, which indicated that it would be more profitable to grow different cultivars in areas naturally low or high in soil nitrogen than to apply additional nitrogen to cultivars adapted to higher fertility levels. Some cultivars, previously considered as intrinsically lower-yielding, may normally receive suboptimal fertilization. Variation in yields of cultivars with nitrogen reflected variation in ear numbers. The grain weight per ear remained relatively constant in 11 cultivars, as changes in weight per grain compensated for changes in number of grains per ear. In contrast, a single cultivar believed to be adapted to fertile prairie conditions was extremely susceptible to nitrogen deficiency, showing a large reduction in the number and aggregate weight of grains per ear. The reduction in ear numbers at high nitrogen levels in some cultivars appeared to be related to temporary crop lodging in the juvenile stage prior to stem elongation. Late cultivars with many long, narrow leaves per tiller and many tillers were most prone to this pseudostem lodging.