Understanding developmental processes responsible for adaptation- and yield- related traits in elite wheat germplasm
- Autores: Priyanka Anantaraddi Basavaraddi
- Directores de la Tesis: Gustavo A. Slafer (dir. tes.), Roxana Savin Parisier (dir. tes.)
- Lectura: En la Universitat de Lleida ( España ) en 2020
- Idioma: español
- Tribunal Calificador de la Tesis: Ignacio Romagosa Clariana (presid.), José Luis Araus Ortega (secret.), Ernesto Igartua Arregui (voc.)
- Programa de doctorado: Programa de Doctorado en Ciencia y Tecnología Agraria y Alimentaria por la Universidad de Lleida
- Materias:
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- Resumen
Increases in wheat yield are essential to meet the growing demand under a complex situation of impossibilities to further expand the arable lands, climate change, and the challenge to produce grains under environmentally friendly techniques. In the past, genetic gains were brought about by optimised plant height and time to anthesis which along with improving lodging resistance and wheat adaptation resulted in an important increase in grain yield. Further genetic gains will mostly depend on other traits, like the duration of particular sub-phases of wheat development or the combination of final leaf number and phyllochron and the effects on floret fertility (a major determinant of the number of grains, and hence grain yield). Therefore, this Thesis was focused on identifying traits underpinning the grain yield and discussing some important trade-offs between physiological components of grain yield as well as to understand the effect of newly identified Eps QTLs on wheat development.
The main aim of the present Thesis was to improve the understanding of the physiological traits underlying grain yield such as distribution of pre-anthesis phases, spike fertility and their influence on grain number. Particularly to identify (i) traits and trait combinations that affect grain yield, evaluating possible genetic variability in pre-anthesis phases in elite lines with similar time to anthesis; and plant height; (ii) the functions of a newly identified Eps QTLs Eps-7D and Eps-2B beyond their known effect on time to anthesis such as their effect on the duration of individual pre-anthesis phases and spike fertility; and (iii) the interaction of the Eps-7D with temperature and photoperiod under controlled conditions. To accomplish these objectives, four experiments under field and one experiment under control conditions were performed.
A large set of bi-parental population derived from elite parents were evaluated under field conditions and sub-set of lines with similar plant height and time to anthesis were selected to identify traits driving the grain yield variability in them. The selected lines carried large variability for grain yield (c. 500-1000 g m-2) which was explained better by spike dry weight at anthesis and fruiting efficiency, determined during late reproductive phase (traits that are components of grain number). Improving grain number did not reduce grain weight as two third of the lines presented high grain number (high grain yield) also had higher grain weight compared to those with low grain number.
Evaluation of eight lines differing in Eps-7D and -2B under field conditions revealed an epistatic interaction between the two QTLs which affected the dynamics of leaf appearance, spikelet and floret primordia development in addition to the duration of pre-anthesis phases. Evaluation of Eps-7D under controlled conditions disclosed the interaction between Eps-7D × temperature on pre-anthesis phases and dynamics of organ development. Overall, the effect of Eps-7D was stronger than Eps-2B and the effects of Eps-7D depended on allelic status of Eps-2B. The allelic forms of Eps-7D, Eps-7D-late and –early, had different degree of sensitivity to temperature and the differences in their effect was clearer at 9 ºC under short day.
The work reported in this Thesis may be useful in further improving grain yield in well adapted wheat regions, as the variability in individual pre-anthesis phases in the studied population with similar time to anthesis carried reasonable variability for grain yield. In addition, the evaluation of allelic combinations of two newly identified Eps and their epistatic interactions help in tailoring allelic combination to produce a desired phenotype with advantageous distribution of time to important phenophases. The interaction between two particular Eps is reported for the first time here which was only speculated before.
