Current Research Projects
Effects of temporal and spatial plant-to-plant variability on maize grain yield have been examined in various studies. Results showed (Tollenaar et al., 2006; Liu et al., 2004a; b; c) that plants within a canopy can compensate for differences in resource capture (i.e., light interception), but the ability to compensate for differences in resource utilization (i.e., kernel number per plant resulting from the particular kernel-set dynamics for the genotype) is very limited, resulting in a decline in harvest index (i.e., grain dry matter as a proportion of total above-ground dry matter) with increasing plant-to-plant variability. This phenomenon is directly related to the improved tolerance to high plant densities of newer maize hybrids. The range in pant dry matter at maturity is in the order of 10 fold when plant density is high. Harvest index is stable in plants within the 90-% upper limit of plant dry matter at maturity and harvest index declines to zero around the threshold plant dry matter for kernel formation. Tolerance to either non-uniform temporal and spatial variability or high plant density is associated with the proportion of plants with total dry matter at maturity that is < threshold plant dry matter for kernel formation (Tollenaar et al., 2006; Liu and Tollenaar, 2009a; b).
The association between stress tolerance, genetic improvement, and plant-to-plant variability for grain yield per plant are examined in the following studies:
- The physiological basis of high plant-density stress. Frequency distribution is determined of individual plant dry matter and harvest index at maturity of genotypes grown at commercial and 2x commercial plant densities for (i) older and newer hybrids and (ii) experimental hybrids that are either tolerant or intolerant to high plant density (hybrids developed by Liz Lee). The response of kernel number per plant to 80-% shade stress during either the spikelet initiation period or the period bracketing silking is also measured in the set of older and newer hybrids.Effect of plant dry matter accumulation on kernel number. Dry matter accumulation is monitored during the life cycle in individual plants of a hybrid and its parental inbred lines grown at three plant densities (medium, high, and very high). Kernel number per plant at maturity is related to rate of development and dry matter accumulation during specific phases of development. Gene-expression profiles of ear samples are examined in plants of (i) equal weight (i.e., in 10-30% weight class), but different ear sizes during the spikelet initiation period and (ii) equal ear size but different plant weight during the silking period.
- Effect of stress on the impact of plant-to-plant variability on grain yield. Early stress such as weed competition may or may not affect grain yield. We postulate that early stress increases plant-to-plant variability and that increased variability can result in yield reduction if plants are subsequently exposed to stress.
Extension Updates
- Corn maturity and heat units
- Frost damage in corn
- Frost update
- Corn development
- Soybean development
- Heterosis in modern single-cross hybrids
Updated: 31 October 2008
© Copyright University of Guelph
