Rosalind A. Bueckert

ATR–FTIR spectroscopy reveals involvement of lipids and proteins of intact pea pollen grains to heat stress tolerance

With climate change, pea will be more frequently subjected to heat stress in semi-arid regions like Saskatchewan during flowering. The pollen germination percentage of two pea cultivars was reduced by heat stress (36°C) with an important decrease in cultivar ‘CDC Golden’ compared to ‘CDC Sage.’ Lipids, protein and other pollen coat compositions of whole intact pollen grains of both pea cultivars were investigated using mid infrared (mid-IR) attenuated total reflectance (ATR)–Fourier transform infrared (FTIR) spectroscopy. Curve fitting of ATR absorbance spectra in the protein region enabled estimation and comparison of different protein secondary structures between the two cultivars. CDC Sage had relatively greater amounts of α-helical structures (48.6–43.6%; band at 1654 cm-1) and smaller amounts of β-sheets (41.3–46%) than CDC Golden. The CDC Golden had higher amounts of β-sheets (46.3–51.7%) compared to α-helical structures (35.3–36.2%). Further, heat stress resulted in prominent changes in the symmetrical and asymmetrical CH2 bands from lipid acyl chain, ester carbonyl band, and carbohydrate region. The intensity of asymmetric and symmetric CH2 vibration of heat stressed CDC Golden was reduced considerably in comparison to the control and the decrease was higher compared to CDC Sage. In addition, CDC Golden showed an increase in intensity at the oxidative band of 3015 cm-1. These results reveal that the whole pollen grains of both pea cultivars responded differently to heat stress. The tolerance of CDC Sage to heat stress (expressed as pollen germination percentage) may be due to its protein richness with α-helical structures which would protect against the destructive effects of dehydration due to heat stress. The low pollen germination percentage of CDC Golden after heat stress may be also due to its sensitivity to lipid changes due to heat stress.

Seed set, pollen morphology and pollen surface composition response to heat stress in field pea

Pea (Pisum sativum L.) is a major legume crop grown in a semi-arid climate in Western Canada, where heat stress affects pollination, seed set and yield. Seed set and pod growth characteristics, along with in vitro percentage pollen germination, pollen tube growth and pollen surface composition, were measured in two pea cultivars (CDC Golden and CDC Sage) subjected to five maximum temperature regimes ranging from 24 to 36 °C. Heat stress reduced percentage pollen germination, pollen tube length, pod length, seed number per pod, and the seed-ovule ratio. Percentage pollen germination of CDC Sage was greater than CDC Golden at 36 °C. No visible morphological differences in pollen grains or the pollen surface were observed between the heat and control-treated pea. However, pollen wall (intine) thickness increased due to heat stress. Mid-infrared attenuated total reflectance (MIR-ATR) spectra revealed that the chemical composition (lipid, proteins and carbohydrates) of each cultivars pollen grains responded differently to heat stress. The lipid region of the pollen coat and exine of CDC Sage was more stable compared with CDC Golden at 36 °C. Secondary derivatives of ATR spectra indicated the presence of two lipid types, with different amounts present in pollen grains from each cultivar.

Review: Annual crop adaptation to abiotic stress on the Canadian prairies: Six case studies

Bueckert, R. A. and Clarke, J. M. 2013. Review: Annual crop adaptation to abiotic stress on the Canadian prairies: Six case studies. Can. J. Plant Sci. 93: 375-385. More than half of Canadas grain crop production comes from the Canadian prairies, a region that experiences short growing seasons characterized by temperature and moisture stress. Historically, the region was dominated by temperate cereal production, but in recent decades crops have included canola (Brassica species) and pulses (chickpea, Cicer arietinum L.; dry bean, Phaseolus vulgaris L.; pea, Pisum sativum L.; lentil, Lens culinaris L.). Here we describe climatic conditions and the resulting abiotic stresses that are common in prairie crop production. We also showcase how specific cultivars have been successfully adapted to fit a short growing season of 95 to 120 d, and examine current strategies to improve crop performance on the Canadian prairies. Durum wheat (Triticum turgidum L. var. durum) production has been increased by incorporating stress escape through early flowering, and stress avoidance through increased seasonal water extraction, water use efficiency and reduced loss from leaves. Dry bean, a warm-season crop, has been improved by selecting for rapid emergence in cool soils. The indeterminate crops chickpea, lentil, and canola (Brassica juncea L.) have been improved through breeding for early flowering, double podding (chickpea), high harvest index, and a longer reproductive duration (lentil and canola). Enhanced drought tolerance in chickpea is in progress using early flowering for drought escape, and rooting traits that improve water extraction and canopy transpiration to avoid water and heat stress. Crops grown on the Canadian prairies have superior quality profiles and two crops, durum and lentil, have become dominant in global exports.

Effect of heat and precipitation on pea yield and reproductive performance in the field

Bueckert, R. A., Wagenhoffer, S., Hnatowich, G. and Warkentin, T. D. 2015. Effect of heat and precipitation on pea yield and reproductive performance in the field. Can. J. Plant Sci. 95: 629-639. Pea (Pisum sativum L.) is important globally as a cool season crop. Pea cultivars are heat-sensitive so our goal was to investigate how weather impacted growth and yield in recent cultivars in the Co-operative pea yield trials (2000 to 2009) for a dryland (Saskatoon) and an irrigated (Outlook) location. We explored relationships between days to maturity, days spent in reproductive growth (flowering to maturity), yield and various weather factors. Yield and the length of reproductive growth increased with seasonal precipitation. Pea was sensitive to heat but heat units did not satisfactorily describe growth and yield in all environments. Strong relationships were observed between crop growth and mean maximum daily temperature experienced during reproductive growth, and between crop growth and mean minimum temperature. The greater the mean maximum temperature (>25.5°C), the fewer the number of days (<35) spent in reproductive growth at the dryland location. At Outlook, 35 to 40 d in reproductive growth occurred in a much wider temperature range from 24.5 to 27°C, and irrigation mitigated some reduction in yield. For dryland pea, more than 20 d in the season above 28°C were associated with less time in reproductive growth and less yield. The threshold maximum temperature for yield reduction in the field was closer to 28°C than 32°C from published studies, and above 17.5°C mean seasonal daily temperature. Western Canadian cultivars currently have short lifecycles, which make them heat sensitive. Heat tolerance could be improved by earlier flowering and a longer duration of flowering via an indeterminate habit. Future research will investigate pea nodal development, flowering and abortion patterns in a range of pea cultivars in field conditions.

Biomass and yield performance of kabuli chickpea cultivars with the fern or unifoliate leaf trait in the Northern Great Plains

Chickpea (Cicer arietinum L.) has two kinds of leaf types, the fern and unifoliate. The best leaf type to use for biomass production and yield in the short growing season of the Northern Great Plains, which has a semiarid environment with end of season rainfall, is not yet known. The objectives of this research were to determine the relationships between leaf type and crop growth rate, maximum above-ground biomass, harvest index and yield under moderate and high plant population densities. The study was conducted in the field at Saskatoon and Swift Current, Saskatchewan, in 2003 and 2004. The experimental treatments consisted of a factorial combination of six commercial kabuli chickpea cultivars representing the two leaf types and two plant population densities: 45 and 85 plants m-2. There were no cultivar and plant population interactions for crop growth rate, maximum above-ground biomass, harvest index and seed yield. Dry matter production was higher in the 2004 season, which had above-average rainfall ...

EFFECTS OF NITROGEN ON REPRODUCTIVE DURATION AND YIELD IN LENTIL CULTIVARS

Reduced nitrogen (N) uptake and N2 fixation during the reproductive growth may reduce the yield in lentil. Five cultivars were grown in two soil media and four N treatments of an inoculated control (NI), and receiving N until flowering (NF), podding (NP) and maturity (NM) in Saskatchewan, Canada. The NF treatment produced the lowest yield, and plants relying on fixation grew larger and yielded more. But NI produced less growth and yield than NP and NM plants, demonstrating that N2 fixation needed improvement for maximal yield. The NP treatment produced the highest yield and more efficiently used N than the later N application in NM. Nitrogen applied at and after mid-pod extended the days to maturity by increasing the reproductive growth period and post-flowering vegetative biomass. Current lentil cultivars require N supply up to at least the mid-pod stage, although the exact stage and timing of N supply need refinement.

Early detection of non-visible sprouting in barley seed using rapid viscosity analysis

Export of grain for malting markets requires viable seed that can withstand storage and shipping conditions. Malting barley is selected for rapid germination. However, barley from the Canadian prairies has minimal dormancy, leading to high risk of sprouting. The goal of this study was to assess the suitability of rapid viscosity analysis (RVA) to detect early non-visible sprouting. Cultivars Harrington (for North America), Alexis (Europe) and CDC Dolly (Western Canada feed barley with low alpha-amylase enzyme activity) were greenhouse grown in Saskatoon, Saskatchewan, and treated in a growth chamber at 12 combinations of t emperature (5 to 22°C) and relative humidity (RH; 60 to 95%) for 1 to 9 d at each of two growth stages, physiological or harvest maturity. Harvested seed from treated plants was measured by RVA, alpha-amylase activity, and germination tests. High RVA final viscosity values (> 150) indicated zero sprouting; RVA 125 nmol CU h-1 were associated with sprouti...

Determination of Photoperiod-Sensitive Phase in Chickpea (Cicer arietinum L.)

Photoperiod is one of the major environmental factors determining time to flower initiation and first flower appearance in plants. In chickpea, photoperiod sensitivity, expressed as delayed to flower under short days (SD) as compared to long days (LD), may change with the growth stage of the crop. Photoperiod-sensitive and -insensitive phases were identified by experiments in which individual plants were reciprocally transferred in a time series from LD to SD and vice versa in growth chambers. Eight chickpea accessions with differing degrees of photoperiod sensitivity were grown in two separate chambers, one of which was adjusted to LD (16 h light/8 h dark) and the other adjusted to SD (10 h light/14 h dark), with temperatures of 22/16°C (12 h light/12 h dark) in both chambers. The accessions included day-neutral (ICCV 96029 and FLIP 98-142C), intermediate (ICC 15294, ICC 8621, ILC 1687, and ICC 8855), and photoperiod-sensitive (CDC Corinne and CDC Frontier) responses. Control plants were grown continuously under the respective photoperiods. Reciprocal transfers of plants between the SD and LD photoperiod treatments were made at seven time points after sowing, customized for each accession based on previous data. Photoperiod sensitivity was detected in intermediate and photoperiod-sensitive accessions. For the day-neutral accession, ICCV 96029, there was no significant difference in the number of days to flowering of the plants grown under SD and LD as well as subsequent transfers. In photoperiod-sensitive accessions, three different phenological phases were identified: a photoperiod-insensitive pre-inductive phase, a photoperiod-sensitive inductive phase, and a photoperiod-insensitive post-inductive phase. The photoperiod-sensitive phase extends after flower initiation to full flower development. Results from this research will help to develop cultivars with shorter pre-inductive photoperiod-insensitive and photoperiod-sensitive phases to fit to regions with short growing seasons.

Light interception and radiation use efficiency of fern- and unifoliate-leaf chickpea cultivars

A chickpea (Cicer arietinum L.) crop with rapid leaf development, high solar radiation interception, and efficient use of radiation can maximize the yield potential in a short-season typical of the Northern Great Plains. This study determined the effects of cultivars varying in leaf architecture on light interception (LI) and radiation use efficiency (RUE) in chickpea. Six kabuli chickpea cultivars with fern and unifoliate-leaf traits were grown under low (45 plants m-2) and high (85 plants m-2) population density at Saskatoon and Swift Current, Saskatchewan, in 2003 and 2004. Fern-leaf cultivars achieved consistently higher maximum LI, and greater cumulative intercepted radiation than cultivars with the unifoliate-leaf. Estimated RUE varied largely with growing season, but did not differ among cultivars or between plant populations. Compared with low plant population, high plant population resulted in greater maximum LI in only 1 out of 4 location-years, but higher cumulative intercepted radiation in 3 o...

High Temperature Effects on in vitro Pollen Germination and Seed Set in Field Pea

Abstract: Prevailing global warming has challenged agricultural production such that it is paramount to evaluate crop cultivars that tolerate increasing temperatures. Heat tolerance in many crops has been screened by examining in vitro pollen germination. The objectives of this study were to determine the effects of high temperature on in vitro pollen germination and pollen tube growth in Pisum sativum L., a crop species adapted to relatively cool temperatures. To evaluate genotypic differences, pollen from 24 cultivars grown in the field was collected and subjected to control (24 °C) and high temperature (36 °C) regimes for 24 h. The latter reduced both in vitro pollen germination percentage and pollen tube growth. Moreover, cultivars differed significantly for in vitro germination of their pollen at high temperatures but not for pollen tube length of germinated grains at 36 °C. In vitro pollen germination was not correlated with seed set parameters of seven of the same cultivars tested in growth chambers at control (24 °C day – 18 °C night) conditions. In contrast, when cultivars were grown at 35 °C day – 18 °C night, pollen germination percentage was positively associated with seed retention, number of seeds per pod, and seed to ovule ratio. Together, these findings corroborate studies in other crops, indicating that in vitro pollen germination represents an accurate screening technique for assessing heat tolerance in field pea.