Abstract
Leaf developmental traits are an important component of crop breeding in small-grain cereals. Surprisingly, little is known about the genetic basis for the differences in barley (Hordeum vulgare L.) leaf development. The two barley row-type classes, i.e., two- and six-rowed, show clear-cut differences in leaf development. To quantify these differences and to measure the genetic component of the phenotypic variance for the leaf developmental differences in both row-type classes we investigated 32 representative spring barley accessions (14 two- and 18 six-rowed accessions) under three independent growth conditions. Leaf mass area is lower in plants grown under greenhouse (GH) conditions due to fewer, smaller, and lighter leaf blades per main culm compared to pot- and soil-grown field plants. Larger and heavier leaf blades of six-rowed barley correlate with higher main culm spike grain yield, spike dry weight, and harvest index; however, smaller leaf area (LA) in two-rowed barley can be attributed to more spikes, tillers, and biological yield (aboveground parts). In general, leaf growth rate was significantly higher between awn primordium and tipping stages. Moderate to very high broad-sense heritabilities (0.67–0.90) were found under all growth conditions, indicating that these traits are predominantly genetically controlled. In addition, our data suggests that GH conditions are suitable for studying leaf developmental traits. Our results also demonstrated that LA impacts single plant yield and can be reconsidered in future breeding programs. Six-rowed spike 1 (Vrs1) is the major determinate of barley row-types, the differences in leaf development between two- and six-rowed barleys may be attributed to the regulation of Vrs1 in these two classes, which needs further testing.
Highlights
Leaf traits and leaf architecture are important for crop adaptation to environmental conditions
For leaf number per main culm, the correlation was stronger in the GH at the awn primordium (AP) stage (r = 0.34 and 0.69 for two- and six-rowed, respectively)
The strong correlation for GH-grown plants at the AP could be attributed to the vernalization period for GH seedlings (4 weeks), which leads to the production of more leaf primordia and more leaves and a delayed AP stage
Summary
Leaf traits and leaf architecture are important for crop adaptation to environmental conditions. Leaf area (LA) is considered to be an indicator of crop growth, development, and plant health, and has a strong relationship with leaf dry weight (LDW) in wheat and barley [1]. Leaf mass area (LMA) reflects the relationship between them, and varies greatly between species due to nutrient and moisture availability, light intensity, and temperature [2,3]. LMA is considered to be a key trait in plant growth [4], plant breeding [5], ecology, agronomy [3], and influences crops’ responses to different growth conditions through changes in LA or/and LDW. Leaf growth rate traits reflect the responses of winter barley to the environment and their relationship with phyllochron [7]. Leaf traits are important for competing against pests, for example, rapid early growth, droopy leaves, high LMA, leaf size, and leaf number can markedly reduce weed growth in rice and wheat [8,9]
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