| | Introduction | Materials and methods | Results and discussion | References
Introduction
A phyllochron is the interval between one leaf appearance and the next, and can be measured using calendar or growing degree days. It is a measurement of plant development that can be used to assess how the plant has responded to environmental conditions or to predict how it is going to respond.
In a previous study on the effects of seeding dates in central Alberta, grain yields of barley varieties were found to decline as seeding was delayed from early May to mid-June (Juskiw et al. 2003; Fig. 1). What was interesting from this study was that there was a link between rapid leaf development (short phyllochron) and ability to have less yield loss under late seeded conditions. The link was independent of maturity of the variety.
The objective of this study was to determine the phyllochrons of barley varieties recently released by Field Crop Development Centre with the potential to use this information to make seeding date recommendations.
Figure 1. Effects of seeding date on relative yield of five barley varieties (from Juskiw and Helm 2003).
Materials and Methods
This study was conducted with plants grown in pots in growth cabinets (Conviron Model PTR15, Controlled Environments Limited, Winnipeg, MB) at 20/15oC, 16/8 h and approx. 450 µ-moles m-2 s-1. Pots were filled with Promix BX (Premier Horticulture Inc., Riviere-du-Loup, PQ), a general purpose growing medium of sphagnum peat moss, perlite, vermiculite, limestone and wetting agent. Pots were watered twice weekly with water and once weekly with fertilizer solution. The varieties used in the study were Kasota, Manny, Niobe, Ponoka, Trochu, Tyto, and Vivar. Kasota, Manny, Tochu, and Vivar are six-rowed, hulled feed types. Niobe and Ponoka are two-rowed, hulled feed types. Tyto is a six-rowed, hulless feed type. Five seeds were planted per pot and thinned to two plants per pot at the 3-4 leaf stage. Leaf counts of the main stem were made on Mondays, Wednesdays, and Fridays from emergence to the flag leaf fully emerged. Final leaf counts of the main stem were recorded.
Leaf counts were regressed against Growing Degree Days (GDD, 0oC basis) using Proc GLM of SAS (SAS Institute, Inc., Cary NC). Phyllochrons were determined as the inverse of the GDD regression co-efficient. As well phyllochrons of individual leaves were determined by dividing growing degree days by leaf count for each sampling time.
Results and Discussion
Excellent fits of leaf number versus GDD were found for all seven cultivars (Fig. 2). Differences in phyllochrons of these seven varieties were found (Table 1). Kasota, Trochu and Tyto had relatively rapid phyllochrons; while Ponoka had a slow phyllochron. The values determined in this study were higher than those reported in Juskiw and Helm (2003) that may reflect a slowing of response under lower light intensities in the growth cabinet versus the field.
Figure 2. Regression of leaf counts against accumulated GDD for seven spring barley varieties.
Table 1. Phyllochrons and Final Leaf Numbers of Seven Barley Varieties.
| Variety | Phyllochron (GDD leaf–1) | Final Leaf Number |
| Kasota | 77 | 8.75 |
| Manny | 87 | 8.00 |
| Niobe | 87 | 9.75 |
| Ponoka | 92 | 9.43 |
| Trochu | 74 | 9.87 |
| Tyto | 72 | 11.00 |
| Vivar | 81 | 9.00 |
The combination of final leaf number and phyllochron can be used to predict relative maturity (in crop modeling a certain number of phyllochrons are assigned to emergence, head emergence, completion of stem elongation, and kernel filling). At a very simplistic level we used final leaf number times phyllochron to come up with a leaf development duration to see how well this was related to relative maturity based on values from the Alberta Agriculture, Food and Rural Development Agdex100/32 (2005) (Table 2). While Tyto had a rapid phyllochron, when this was combined with its high leaf number, it resulted in a long leaf development duration that was also reflected in its maturity. Kasota combined a rapid phyllochron with low leaf number to have a short leaf development duration that reflected its early maturity. Using phyllochron to estimate maturity would over-estimate the maturity for Niobe; and under-estimate that of Manny and Vivar. Further study is needed to reconcile such differences if phyllochrons are to be used for predictive purposes.
Table 2. Leaf Development Duration and Its Relationship to Maturity for Seven Barley Varieties.
| Variety | Maturity
(d)z | Duration of leaf development
(GDD) | Relationship of maturity/Leaf
GDD duration |
| Kasota | 94 | 670 | early/early |
| Manny | 97 | 700 | mid/early (?) |
| Niobe | 97 | 850 | mid/late (?) |
| Ponoka | 100 | 870 | late/late |
| Trochu | 96 | 730 | mid-early/mid-early |
| Tyto | 98 | 790 | mid-late/mid-late |
| Vivar | 98 | 730 | mid-late/mid-early (?) |
z Maturities from Alberta Agriculture, food and Rural Development (2005)
While there was good fit of the linear regression of leaf number versus GDD, when phyllochrons were estimated using the leaf count at each sampling time, we found that the phyllochrons for the first two leaves were often slower than for subsequent leaves (Fig 3.). There were two distinct patterns: 1) six-rowed cultivars had slow initial phyllochrons followed by more rapid initiation of subsequent leaves; and 2) two-rowed cultivars, especially Niobe, had more rapid initiation of the first two leaves followed by slower initiation of subsequent leaves. What effect these differences in initiation rates would have on competition needs further study.
Figure 3. Phyllochron estimates for individual leaves for seven spring barley varieties.
As a final point, we took our long term yield data from 1998 and 2002 at Lacombe and Stettler and compared yield differences between early and late May planting dates for the varieties under study (Fig. 4 and 5). This was just a quick look to see if a recommendation based on rapid phyllochrons would be valid. The late planting was generally before the end of May at either location and would not be considered extremely late, so the data is of limited value. Our recommendation based on phyllochrons would be that Tyto, Trochu and Kasota would be the varieties of choice. However Trochu had one of the greatest drops in yield from early or mid-May plantings to the late May planting. Overall, Ponoka, Tyto and Vivar had the least yield reductions with the later planting. While we would like to make a clear-cut recommendation to plant Tyto, Trochu or Kasota when faced with late seeding, further field work is needed to confirm or refute the phyllochron, late-seeding yield response relationship.
Figure 4. Yield response to seeding dates at Lacombe from 1998 to 2003 (where early was the first week of May and late was the last week of May).
Figure 5. Yield response to seeding dates at Stettler from 1998 to 2003 (where mid was the second week of May and late was the last week of May).
References
Alberta Agriculture, Food and Rural Development. 2005. Varieties of Cereals and Oilseed Crops for Alberta - 2005. Agdex 100/32.
Juskiw, P.E. and Helm, J.H. 2003. Barley response to seeding date in central Alberta. Can. J. Plant Sci. 83:275-281.
Pat Juskiw, Jim Helm and Joseph Nyachiro
Field Crop Development Centre, 5030-50 Street, Lacombe AB T4L 1W8
Presented at the 18th North American Barley Researchers Workshop, July 17-20, 2005 |
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