Malcolm J. Morrison

Regulation of seed yield and agronomic characters by photoperiod sensitivity and growth habit genes in soybean

Soybean genotypes are adapted to narrow bands of latitude due to photoperiod sensitivity. There are several photoperiod-sensitive loci (E1, E2, E3, E4, E5, E6, E7, E8). Determinate and indeterminate growth habits are controlled by a single locus. The objective of our research was to examine the effects of photoperiod sensitivity and growth habit alleles on seed yield and other agronomic characters using isogenic lines. Twenty ‘Harosoy’ isolines with 11 photoperiod-sensitive genotypes many with both indeterminate and determinate growth habits were grown in the field at Ottawa, ON, from 2003 to 2007. Maturity ranged from 97 to 127 days, and seed yield increased linearly with maturity until about 112 days when it plateaued. Determinate lines were always shorter than indeterminate lines of equivalent maturity. Seed yield was associated with plant height, maturity, seed sugar concentration, seed weight and lodging. Effects of alleles at individual loci, and additive and epistatic effects across multiple loci were examined. At a single locus, photoperiod-insensitive alleles produced isolines that matured 8–11 days earlier, yielded less, and had shorter plants with reduced lodging. In multiple loci analyses, additive effects explained most of the variation in agronomic characters since additive models with E1, E3, E4, E7 and Dt1 loci included compared well to additive plus epistatic models and genotype-based models. Variation in photoperiod sensitivity and growth habit alleles results in a range of maturity, with pleiotropic effects on seed yield and agronomic characteristics, and play an important role in providing adaptation across latitudes.

Drivers of trends in Australian canola productivity and future prospects

In Australia, canola was initially grown in more reliable rainfall areas (G>400mm annual rainfall) due to its greater sensitivity to heat and drought than cereals, and the higher production costs increasing risk in more marginal environments (Colton and Potter, 1999). Improved varieties and agronomy, along with the overall farming systems benefits of weed and disease control in cereals, have expanded the area cultivated under canola, and it is now grown in all but the driest margins of the wheat belt.

Canola yield improvement on the Canadian Prairies from 2000 to 2013

Abstract. During the period from 2000 to 2013, average canola yields from Canadian farms increased from 1330 to 2025 kg ha–1, or 54 kg ha–1 year–1. The objective of this review was to propose likely reasons behind this increase by examining genotypic, environmental and agronomic factors. During this period, hybrid canola cultivars with herbicide tolerance (HY-HT) expanded from 80% to >95% of the area sown to canola. Genetic gain from switching from open-pollinated cultivars to HY-HT cultivars was estimated to account for 32 kg ha–1 year–1. When some key environmental factors were examined, there were no significant linear changes in growing season temperature, although the linear increase in April and May precipitation was significant and likely responsible for an increase of 12 kg ha–1 year–1. When coupled with the yield increase from changes in atmospheric CO2 (3 kg ha–1 year–1), the environment was estimated to account for ∼15 kg ha–1 year–1. Ignoring all main-factor interactions, changes due to management accounted for the remainder, or 7 kg ha–1 year–1. The expanded use of HY-HT varieties has resulted in better weed control, and an increase in the use of minimum tillage, leading to greater water-use efficiency and higher yield. It is likely that many of the effects of changes in management were hidden in the interaction with genotype and environment main effects. It is difficult to estimate these interactions without designing experiments to do so. The design and implementation of experiments to understand the interaction among main factors should be a priority. Future yield targets of 25 Mt canola by 2025 will require an increase in yield per ha beyond the current rate, or an increase in the land seeded to canola, or a combination of the two factors. Continued progress with canola yield depends on active plant-breeding programs, agronomic research using new varieties, favourable environmental conditions, and high world commodity prices.

Effect of seed treatments on emergence, yield, and root rot severity of soybean under Rhizoctonia solani inoculated field conditions in Ontario

Field trials were conducted with soybean at two sites each year from 2001 to 2003 in Ottawa, ON, to determine the effect of seed treatments with various combinations of seven formulated fungicides and the bioagent Yield Shield (Bacillus pumilus GB34) under Rhizoctonia solani inoculated conditions. Controls were untreated seed planted into both non-inoculated (natural) soil and soil inoculated with R. solani. Compared with the non-inoculated control, inoculation significantly increased root rot severity and reduced emergence by 27%, and yield by 31%. Under the inoculated conditions, none of the seed treatments significantly increased emergence or yield in all of the six trials when compared with the control. Allegiance (metalaxyl) plus Vitaflo-280 (carbathiin plus thiram) and Vitaflo-280 alone were the most effective seed treatments, increasing emergence in by 20 and 19% and yield by 21 and 26%, which were significantly better than the control in four and five trials for emergence and three and four trials...

Quantifying the Effects of Photoperiod, Temperature and Daily Irradiance on Flowering Time of Soybean Isolines

Soybean isolines with different combinations of photoperiod sensitivity alleles were planted in a greenhouse at different times during the year resulting in natural variation in daily incident irradiance and duration. The time from planting to first flower were observed. Mathematical models, using additive and multiplicative modes, were developed to quantify the effect of photoperiod, temperature, photoperiod-temperature interactions, rate of photoperiod change, and daily solar irradiance on flowering time. Observed flowering times correlated with predicted times (R2 = 0.92, Standard Error of the Estimate (SSE) = 2.84 d, multiplicative mode; R2 = 0.91, SSE = 2.88 d, additive mode). The addition of a rate of photoperiod change function and an irradiance function to the temperature and photoperiod functions improved the accuracy of flowering time prediction. The addition of a modified photoperiod function, which allowed for photoperiod sensitivity at shorter photoperiods, improved prediction of flowering time. Both increasing and decreasing rate of photoperiod change, as well as low levels of daily irradiance delayed flowering in soybean. The complete model, which included terms for the rate of photoperiod change, photoperiod, temperature and irradiance, predicted time to first flower in soybean across a range of environmental conditions with an SEE of 3.6 days when tested with independent data.

When is short-season soybean most susceptible to water stress?

Fourteen soybean (Glycine max L. Merr.) cultivars were grown at Ottawa from 1993 to 2004 in a replicated design. Phenology, yield and seed quality data were collected. Climate data were merged into the data set. Seven key phenological growth stages were identified and the total precipitation (ppt) between stages was calculated per cultivar for all possible durations. Mean cumulative ppt among the growth stage durations was correlated with mean seed yield, 1000-seed weight (tsw) seed protein and oil content. Variation in ppt prior to flowering did not influence yield. Yield and tsw were found to be most susceptible to water stress from flowering to the end of seed development. The most sensitive stage occurred during a period from the beginning to the end of pod development (R4 to mid R5). Seed protein was correlated with ppt from the beginning of flowering to the beginning of seed development. Seed oil content was reduced by late season precipitation. The identification of the most sensitive stage of deve...

Characterising canola pollen germination across a temperature gradient

Abstract. If predictions are correct, heat stress during reproduction will become a yield limiting factor in many world crops and breeding heat stress tolerance a major goal. The objective of our paper was to highlight a novel system to investigate the influence of temperature (T) on pollen germination using a thermal gradient PCR programmed to establish differential Ts across 12 wells of a PCR plate. Seven cultivars of Brassica napus L. were grown through flowering in a cool growth cabinet (20/15°C day/night) or a heat stress cabinet (HST, 27/22°C day/night). Pollen from each cultivar × cabinet combination was aspirated from 6 opened flowers, and suspended in germination media. Drops of the pollen suspension were floated on media in each well, and the PCR T was set to 30°C with a gradient of ± 10°C, creating a range from ∼20 to 40°C from left to right. After an 8 h treatment, the pollen germination (pg, %) and pollen tube growth score (ptg, 1–5) were evaluated using a microscope. There were significant differences among cultivars for pg and ptg score and significant differences among well T for pg and ptg score. Pollen tubes grew best at T from 20 to 23°C. Well T exceeding 33°C reduced pg and ptg score, although 3 of the 8 cultivars had good pg even at 36°C. HST >29°C, in a growth cabinet, generally resulted in B. napus raceme sterility, although our experiment showed that pollen was still capable of germinating up to 33°C, indicating that pollen germination may not be the only reason for heat stress susceptibility.

Biological nitrogen fixation by pulse crops on semiarid Canadian prairies

Abstract: Pulses play a significant role in nitrogen cycling as they fix atmospheric N2 through symbiosis. However, it is unknown whether there are differences in the ability of biological nitrogen fixation (BNF) among pulse species and individual cultivars. Here, we quantified the BNF ability of selected pulse cultivars and determined the effect on crop yield. A total of 25 species-cultivar combinations of chickpea (Cicer arietinum L.), dry bean (Phaseolus vulgaris L.), faba bean (Vicia faba L.), field pea (Pisum sativum L.), and lentil (Lens culinaris Medik.) were tested in 2008–2010. Pulses had a higher BNF in the wetter 2010 season, and a lower BNF in the drier 2009 season. In 2010, faba bean and chickpea had the highest BNF at 106 kg N ha-1, followed by lentil, field pea, and dry bean at 87, 69, and 12 kg N ha-1, respectively. Across years, field pea had the most stable BNF ability, fixing 55 kg N ha-1 with an average seed yield of 2418 kg ha-1. There are large differences in BNF and yield among cultivars within a species and the magnitude of the difference varied with years. Large genetic variability in BNF and yield suggest the possibility that pulse cultivars with a higher N2-fixing ability and seed yield can be developed through selection of the N2-fixing trait.

Increasing stalk sucrose in sugarcorn (Zea mays L.): genetic analysis and preliminary breeding

The generation of biofuels from biomass such as corn (Zea mays L.) stalks may be improved by increasing the concentration of available sugar. Understanding the inheritance of high stalk sugar traits is important for the development of new hybrids adapted for this purpose. The genetics associated with high stalk sugar (measured as sucrose equivalents) concentration was investigated by conducting a diallel analysis of six adapted inbred lines varying in stalk sucrose concentration, and a generation mean analysis using high and low sucrose inbred lines as parents tested in multiple years. Changes in stalk sucrose concentrations for six families with repeated cycles of selfing and selection over seven generations was also investigated. Results of the diallel and the generation means analysis of stalk sugar traits revealed that both additive [general combining ability (GCA)] and non-additive gene effects [specific combining ability (SCA)] were important for the inheritance of these traits and their expression was influenced by environment. Additive gene actions were more important than non-additive gene actions for controlling these traits. The study also demonstrated that the hybrid combinations of C103 with 73353 for stalk sucrose and with CO384 for stalk juice may be the best candidates for increasing stalk sugar as these inbreds had high means for these traits with favourable SCA estimates and at least one inbred had high GCA. Substantial increase in stalk sucrose in six different families over seven generations using a pedigree breeding method showed that selection gains could be made following this procedure.

Modelling soybean yield responses to seeding date under projected climate change scenarios

Abstract: Climate change is projected to increase growing season length and temperature in Canada but how soybean [Glycine max (L.) Merr.] will respond is uncertain. By modelling soybean responses to climate change scenarios, stakeholders can develop adaptation strategies. The CSM-CROPGRO-Soybean and STICS models were used to simulate soybean responses under baseline (1971–2000) and in near (2041–2070) and distant (2071–2100) future climate scenarios, including those resulting in altered seeding dates in eastern Canada. Field data collected in Ottawa were used to evaluate the models. The simulated seed yield using the CSM-CROPGRO-Soybean model showed an increase of about 14% (0.34 t ha-1) in the near future and a decrease in the distant future under RCP8.5 and the STICS model estimated a decrease in both the near and distant future. When the crop parameters determining the life cycle were increased by 30% and 40%, the simulated seed yield increased by more than 5%–10% and 10%–20% and by more than 20%–30% and 27%–40% if combined with current harvest index levels. Our simulations showed that soybean seed yield would not benefit from a prolonged growing season under the projected future climate in eastern Canada, unless harvest index is maintained.