Novo PRŽULJ1,5*, Vojislava MOMČILOVIĆ2, Milan MIROSAVLJEVIĆ2, Zoran JOVOVIĆ3, Dragan MANDIĆ4, Miloš NOŽINIĆ4
1Faculty of Agriculture, University of Banja Luka, Bosnia and Herzegovina
2Institute of Field and Vegetable Crops, Novi Sad, Serbia
3Biotechnical Faculty, University of Montenegro, Montenegro
4Agricultural Institute of the Republic of Srpska, Banja Luka, Bosnia and Herzegovina
5Faculty of Agriculture, University of East Sarajevo, Bosnia and Herzegovina
*Corresponding author: [email protected]
Abstract
Interval between appearance of successive leaves (phyllochron, PI) in grasses is determined by timing of leaf initiation at the stem apex and duration of leaf tip elongation through the whorl of mature sheaths. The objective of this study was to evaluate PI of main stem leave (MSL) development during tillering of six spring barley varieties, which differed in origin, earliness, spike type and some other traits. The studies were carried out in the field at the Institute of Field and Vegetable Crops Novi Sad, Serbia (45°20'N, 15°51'E, 86m asl) during 1999-2001 period. The experiments were arranged in a randomized complete block design with three replications and planting rate of 200 viable seeds per m-2. Three random plants in each plot were labeled for monitoring during growing. PI was estimated every 2-3 days using Haun scale. Growing-degree-days (GDD) were used as time scale with base temperature of 0°C. PI was the reciprocal of the slope determined by regression of MSL against GDD using data from each plant within a cultivar. When plotted against thermal time leaf appearance was a strictly linear function of temperature. Across cultivars, the lowest PI was in 2000 81 GDD and the highest in 2001 89 GDD. Across years and leaves PI arranged from 65.5 in the variety Gustoe to 80.1 in the variety Jelen. All three factors, i.e., year, variety, and their interaction, were included in the PI determination of the first leaf. In all three years, first leaf demanded more days for appearance due to lower temperatures and shorter daylength. Of all six leaves studied, the second leaf was most strongly influenced by genetic constitution of cultivars and 75% of total variation belonged to this component of variation. Variation of PI of the third, fourth and fifth leaf was mainly determined by interaction GxY and year. It seems that in our investigation temperatures had a strong effect on leaf appearance. The linearity suggests that MSL stage can be used as a predictive measure of plant development and it can retroactively show the quality of the preemergent seedbed environment.
Keywords: Spring barley (Hordeum vulgare L.), phyllochron, Haun scale, tillering, growing degree days
Introduction
Morphological changes of barley plant can be used for the evaluation of both, plant development and growth environment (Klepper et al., 1982; Rickman et al., 1983). Mainstem leaf (MSL) appearance and proportion of tiller formation are parameters useful for the evaluation of germination and vegetative development. Haun (1973) developed a scale which quantitatively describes the vegetative developmental stages in spring wheat. The time spent for leaf elongation, i.e., the time from leaf appearance to the appearance of the next leaf,
emergence is positively related with MSL (Krenzer and Nipp, 1991). Smaller PI, i.e., lower GDD, represents faster development and leaf appearance. PI is influenced by temperature and daylength (Cao and Moss, 1989a; 1989b). Baker et al. (1986) found a decrease and Kenzer et al. (1991) found an increase in PI in wheat under water deficit conditions, while Bauer et al.
(1984) did not establish a dependence of MSL appearance on soil moisture content.
Investigations of Dofing (1995) and Sharratt (1999) referred to the subarctic environment, while little is known about MSL growth of spring barley in semiarid conditions of growing.
The objective of this study was to evaluate MSL development during tillering of spring barleys, which differed in origin, earliness, spike type and some other traits, grown in a semiarid environment.
Material and Methods
Field trials. Six spring barley varieties were grown in Novi Sad, (45° 20’ N, 15° 51’ E, 86m asl) from 1999 to 2001. The experiments were arranged in a randomized complete block design with three replications with plots 2m long and 1m wide, containing 6 rows 20 cm apart. The planting rate was 200 viable seeds per m-2. Three random plants in each plot were labeled for monitoring during growing. Phyllochron was estimated every 2-3 days using Haun scale (Haun, 1973). Growing-degree-days (GDD) were used as time scale with base temperature of 0°C.
PI, measured as GDD per leaf, was the reciprocal of the slope determined by regression of MSL against GDD using data from each plant within a cultivar (Baker et al., 1986). Only MSL measurements greater than or equal to 1.0 were used in the regression because it is difficult to estimate partial emergence of the first leaf since there is no antecedent leaf for comparison.
Statistical analysis. A mixed model was used with varieties considered as fixed and years as random effects (Zar, 1996). Heritability for a single year was estimated as the ratio
2G/2G+2E, (Singh et al., 1993).
Weather. At the time of planting in 1999, the mean daily temperature was increased and this year had the highest sum (Σ=52ºC) in pre-emergence period (Figure 1). The amount of available water during that period was appropriate. In the period following first leaf appearance, there occurred a temperature decrease and a water deficit. In the last third of March, the temperatures were moderate, with a slow increasing trend, and a water deficit was recorded. In the year 2000, low temperatures persisted till the last third of March, with the lowest temperature sums for 10-day periods among the three years (Figure 1). From the middle of the last third of March, the temperature continually increased. Water deficit was again recorded in this year. In 2001, low temperatures were recorded till the end of February and after that they continually increased till the end of tillering. The periods of emergence and tillering in this year were well supplied with water.
Figure 1. Ten-day average air temperature (_____) and total ten-day precipitation (---) in 1999, 2000, and 2001 growing seasons of spring barley in Novi Sad
Results and Discussion
ANOVA showed that all three factors, i.e., year, variety, and their interaction, were included in the phyllochron determination of the first leaf (Table 1). The phyllochron of the first leaf was not precisely defined, since GDD from sowing to first leaf appearance was supposed to be the phyllochron. Year had a lower range of variation than variety (Table 2), although its component of variance was higher. Across cultivars, the lowest phyllochron was in 1999 and the highest in 2001 (Table 3). The Russian six-rowed variety Avans had the longest phylochron interval for first leaf appearance. Interaction GxY occurred in all cultivars; Jelen, Nora, Alexis, and NS-135 had the shortest PI in 1999 while differences in the other two years could not be established. Avans significantly differed in all three years, while Gustoe had longer PI in 2001 than in the previous two years (data not shown). Significance of variety in first leaf appearance was also confirmed by a high value of heritability (Table 1).
0
15-20 II 21-29 II 1-10 III 11-20 III 21-31 III 1-10 IV 11-20 IV 21-30 IV
0
15-20 II 21-29 II 1-10 III 11-20 III 21-31 III 1-10 IV 11-20 IV 21-30 IV 0
15-20 II 21-29 II 1-10 III 11-20 III 21-31 III 1-10 IV 11-20 IV 21-30 IV
47/22 99/3 53/1 108/2 124/15 126/7 141/28
Table 1. ANOVA and percentage of components of variance for phyllochron during tillering of six spring barley varieties in 1999-2001
*,** Significant at 0.05 and 0.01 level, respectively;
ns - not significant
In 1999, high temperatures during emergence caused a faster second leaf development so that it appeared 214.5 GDD after sowing (from Table 4). Low mean daily temperatures and water deficit after first leaf development in that year caused relatively more days for the second leaf appearance in relation to the other two years. Year did not effect second leaf appearance (Table 1) and PI across cultivars ranged from 72.1 in 1999 to 77.8 GDD in 2001 (Table 3).
Total sum of GDD from sowing to second leaf appearance was shortest in 1999 (214.5) and longest in 2001 (245.6). Of all six leaves studied, the second leaf was most strongly influenced by genetic constitution of cultivars and 75% of total variation belonged to this component of variation (Table 1). Range of variation for cultivars was from 53.3 (Nora) to 125.2 GDD (Gustoe) (Table 2).
The two-rowed cultivars had shorter phyllochron of the second leaf than the six-rowed cultivars. Thermal requirements for the second leaf were consistent among years in the two-rowed cultivars, while significant differences occurred in all three six-rowed cultivars. High heritability values (Table 1) showed that the established variability for second leaf appearance was under strong genetic control.
Variation of phyllochron of the next three leaves, third, fourth and fifth, was mainly determined by interaction GxY and year (Table 1). In the components of variance, year participated from 5 to 30% and interaction from 53 to 75% of total variation (Table 1). Range for variation for these leaves, similar to the previous two, was larger among years than among cultivars (Table 2). The shortest PI for these three leaves was registered in 2000.
Table 2. Ranges of cultivar and year mean values for phyllochron during tillering in six spring barley varieties in
Table 3. Means of phyllochron across cultivars and years in GDD during tillering of six spring barley varieties in 1999-2001 growing seasons Year 1st leaf 2nd leaf 3rd leaf 4th leaf 5th leaf 6th leaf
The third and fifth leaf had close phyllochrons in 1999 and 2000, while the fourth leaf had the longest PI in 1999 and similar lengths of PI in the other two years. GxY interaction for these three leaves occurred in almost all cultivars. Variation in third leaf appearance was mainly controlled by cultivar, while about one third of variation in fourth and fifth leaf appearance was due to non-genetic factors. GxY interaction had the highest responsibility for PI of the
sixth leaf.
Figure 2. Heat units (GDD) required for the leaf appearance in six spring barley cultivars (_____ illustrates regression of leaf appearance against GDD for each investigated variety, --- illustrates regression of average values of the six cultivars against GDD)
Variation across cultivars, i.e., among years, was minor, while across years it varied from 61.3 to 86.6 (Table 2). The cultivars Jelen and Gustoe did not differ in the phyllochron of the sixth leaf, while the other cultivars showed significant differences among the three years (data not shown). There was no consistency in the differences in PI among the cultivars; Alexis had the longer PI in 2000 NS-135 in 1999 and Avans the shortest in 2001.
y = 0,0121x - 0,5318
The differences in the heat units for first leaf appearance suggest that the cultivars responded to accumulated GDD at this phase which agrees with observations of Baker et al. (1986) and Bauer et al. (1984). Avans and Gustoe originated from different ecological conditions in relation to the location of this experiment and it could be partially the reason for longer PI of the first leaf. Fast and uniform seedling emergence is especially desirable in short-season areas (semiartic, semiarid, arid), which provides adequate plant stand and establishment of effective plant canopy structure and yield. Early emerging seedlings have a longer time for growth in relation to late emerging ones. The results of early emergence is higher tillering, i.e., higher grain yield (Gan et al., 1992).
In all three years, first leaf demanded more days for appearance due to lower temperatures and shorter daylength. Cao and Moss (1989a), found that decrease in phyllochron interval and increase in the rate of leaf appearance (leaves day-1) was associated with increase in daylength. It seems that in our investigation temperatures had a strong effect on leaf appearance. Indeed, in 1999, temperatures during sowing and germination were rather high and the first leaf appeared soon after sowing; after that, the temperatures dropped and more days were required for second leaf appearance (Figure 1). Water deficit that occurred at the time of sowing in 1999 could also be responsible for the increased rate of first leaf appearance. Baker et al. (1986) found lower PI values in wheat under non-irrigated field conditions, i.e., a higher rate of mainstem leaf. High air temperature at the time of sowing and emergence is expected to cause longer PI. That was confirmed in this study where high temperatures in the first 10 days of March 2001 (Figure 2, sum of mean daily temperature was 117˚C) caused the longest PI of the first leaf in the three years. Appearance of the other five leaves in 1999 and all leaves in 2001 was in close symmetrical intervals, since temperatures were steady and without large fluctuations. In 2000, temperatures were lowest among the three years and the appearance of the first leaf was latest.
The relation between leaf development and GDD as illustrated in Figure 2 shows the close dependence of leaf development on accumulated GDD. The coefficients of determination (R2) were 0.92, 0.98, and 0.95 for 1999, 2000, and 2001, respectively, indicating that leaf development was mainly influenced by thermal conditions. Sharratt (1999) also reported high values of coefficients of regression for two spring barleys grown in interior Alaska (R2=0.98 and R2=0.95). These results are consistent with Kleper et al. (1982), whose results were the basis for suggesting a linear relationship between GDD and leaf emergence. The high dependence of spring barley leaf appearance on temperature found in this investigation confirmed the previously determined thermal requirements for leaf development in small grains.
Leaf appearance is a highly heritable trait and there is a strong relationship with accumulated thermal units. The linearity suggests that MSL stage can be used as a predictive measure of plant development. Also it can retroactively show the quality of the preemergent seedbed environment.
Conclusions
Results from this study showed the high heritability of phyllochron in barley. High temperature and water deficit increase rate of mainstem leaf appearance. Selection for small phyllochron had the desirable indirect effect on reducing time to maturity, but could also reduce grain yield when not accompanied by an increase in leaf number. These results indicate that phyllochron is a good measure of plant development, and that it is associated with time to maturity and other developmental traits.
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PHENOLOGICAL AND POMOLOGICAL ANALYSIS OF FRUIT