9:00 am - 10:00 am
A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Dinithi Kumarapeli. This seminar is open to the general public to attend.
Video call link: https://meet.google.com/sfy-wcgn-wee
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Thesis Topic: Effect of heat stress on reproductive development of wheat (Triticum aestivum L.)
MSc with Dr. Jocelyn Ozga.
Rising global atmospheric temperature can negatively affect the reproductive development of crops including wheat (Triticum aestivum L.) which can ultimately lead to a reduction in seed set and yield. The aim of this study was to determine the effect of moderate heat stress (35°C per 6 h per day for 8 days) imposed during early flowering (beginning at BBCH 37 stage; when the flag leaf is just visible) on the reproductive morphology, pollen viability, and grain yield in selected heat-sensitive and heat-resistant recombinant inbred lines (RILs) of wheat derived from a ‘CDC Go’ X ‘Attila’ RIL population where the parents segregate for heat resistance with respect to grain yield. A general response to heat stress across the RILs and parental lines was to reduce the growth of the main tiller and anthers potentially allowing the sensitive stages of reproductive development to complete with reduced exposure to the negative effects of heat stress. Reduction of tiller growth under heat stress could also facilitate an adequate supply of photoassimilate to developing grains. The most heat-sensitive RIL assessed (RIL 131) exhibited reduced pollen viability and an increase in ovule size under heat stress conditions at anthesis indicating abnormal reproductive development. The spike and spikelet length at anthesis were also greater in RIL 131 under heat stress conditions suggesting a more favorable partitioning of assimilates to the tissues that will surround the developing grain which may negatively affect grain development. Heat-resistant RILs maintained grain yield under heat stress by maintaining pollen viability and ovule size indicative of normal reproductive development. Reduced spikelet length also appeared to be a common trait in heat-resistant lines, indicative of more favorable partitioning of assimilates to the developing grain than the surrounding floral structures.
The application of 4-Cl-IAA prior to heat stress in RIL 137 increased grain yield under heat stress conditions but did not affect any morphological parameters assessed. These data suggest that auxin potentially facilitated photoassimilate partitioning to the developing grains thereby maintaining grain yield under heat stress conditions.
The presence of Rht-B1b mutant allele in the heat-sensitive RIL 131 and parent ‘CDC Go’ may enhance the photoassimilate supply to developing florets under control conditions by reducing stem elongation, but this alone did not improve grain yield under heat stress in these lines. Overall, these data confirm previous studies that heat stress can negatively affect reproductive development in wheat reducing grain yield. Heat-resistant RILs maintained normal grain yield under heat stress by maintaining pollen viability, reducing the growth of tillers and anthers potentially to complete development more rapidly to minimize exposure heat stress, and reducing growth in other tissues peripheral to the developing grains to facilitate adequate photoassimilate supply to the latter.