Yield and quality response of spring wheat cultivars to post anthesis high temperature

Thesis (M.Sc.Agric.) -- University of Stellenbosch, 1999.

ENGLISH ABSTRACT: Knowledge of the growth, yield and quality response of spring wheat cultivars to high temperatures is important to minimise variation that often exists in yield and breadbaking quality of wheat produced in warmer regions. To achieve this, four South African spring wheat cultivars Kariega, Palmiet, SST 55 and SST 57 were grown under controlled conditions at the University of Stellenbosch during 1998 at temperature regimes of 15/10, 20/15, 25/20 and 30/25°C during grain filling. From seeding till anthesis, plants were grown at a temperature of 15/10°C. In this study,. the highest temperature regime of 30/25°C affected all parameters tested, while at lower temperature regimes cultivars responded differently. The 30/25°C temperature regime caused premature senescence of the leaf area which was attributed to a decrease in relative leaf water content. Increased senescence of leaves at this temperature regime, reduced photosynthesis during grain filling, with the result that shriveled kernels with a lower mass kernel -1 were produced and yield plant -1 was reduced by almost 50% compared to that of the control (15/100 C). Other yield components such as kernels ear -1 were less reduced and Kariega was less affected in comparison with the other cultivars. High temperature regimes of 30/25°C during grain filling resulted in increased flour protein content. Mixogram peak heights increased as post-anthesis temperature regimes increased, while Palmiet also showed an increase in dough development time with increasing temperatures. At the highest temperature regime (30/25°C), the respective dough development times for SST 55 and SST 57 were well below the optimum mixing time of 2.5 to 3 minutes set by the baking industry, while the mixograph band widths of Kariega were the narrowest at all temperature regimes tested. This tendency indicated good water absorption properties. These results indicate that quality parameters of Kariega and Palmiet are less sensitive to high post-anthesis temperatures in comparison with SST 55 and SST 57. In general, it is concluded that although this study showed small differences between cultivars, Kariega was consistently different from other cultivars, indicating possible adaptation to hotter environments. However, more cultivars need to be screened before recommendations for such areas can be made.

AFRIKAANSE OPSOMMING: Kennis aangaande die groei-, opbrengs- en kwaliteisreaksie van lente koringcultivars teenoor hoe temperature is belangrik. Dit mag help om jaar tot variase ten opsigte van opbrengs en bakkwaliteit wat dikwels in warmer produksiegebiede voorkom, te verminder. In hierdie studie is die invloed van vier dag/nagtemperatuur-behandelings wat gedurende korrelvulling op die Suid-Afrikaanse lente koringcultivars, Karige, Palmiet, SST 55 en SST 57 toegepas is, ondersoek. Die ondersoek is gedurende 1998 onder gekontroleerde groeitoestande by die Universiteit van Stellenbosch uitgevoer. Vanaf planttyd tot antese is aile plante gegroei by 'n dag/nagtemperature van 15/10oC. Vanaf antese tot oes is die kontrole plante steeds aan hierdie temperatuur blootgestel, terwyl die ander plante aan dag/nagtemperature van onderskeidelik 20/15°C, 25/200C en 30/25°C blootgestel is. In hierdie studie is aile gemete eienskappe deur die hoogste dag/nag tempertaure beinvloed en het cultivars nie grooteliks verskil in hul reaksie nie. Verskille in cultivarreaksie het wei by die laer dag/nagtemperature voorgekom. Die 30/25°C temperatuurbehandeling het blaarafsterwing versnel weens 'n verlaging in die relatiewe water inhoud van die blare. Dit het blaaroppervlakte-duurte en dus ook fotosintese gedurende korrelvulling benadeel met die gevolg dat verkrimpte, maer korrels geproduseer en opbrengs plant-1, in vergelyking--met die kontrole plante, met byna 50% verlaag is. Ander opbrengskomponente soos korrels aar -1 is minder ernstig benadeel en Kariega was ietwat meer tolerant as die ander cultivars. Hoe dag/nagtemperatuurgedurende korrelvulling het tot 'n toename in meelproteieninhoud aanleiding gegee. Mixogram-piekhoogtes het ook toegeneem met toenemende temperature. In teenstelling met ander cultivars het Palmiet ook 'n toename in deegontwikkelingstyd getoon. By die hoogste dag/nagtemperatuur (30/25°C) was deegontwikkelingstye van die cultivars SST 55 en SST 57 betekenisvol laer as die optimum tye van 2.5 - 3.0 minute wat deur die bakbedryf vereis word. Waardes vir Kariega was meer aanvaarbaar en mixogram bandbreedtes vir kariega was ook by aile temperatuurbehandelings die smalste. Dit is 'n aanduiding van goeie waterabsorpsie-einskappe. Hierdie resultate toon dat die bakkwaliteit van Kariega en Palmiet minder gevoelig is vir hoe temperature gedurende korrlevulling in vergelyking met SST 55 en SST 57. In hierdie studie is gevind dat hoewel verskille in cultivareaksie oor die algemeen klein was, Kariega ietwat beter aanpassing by die hoe temperature getoon het. Meer cultivars sal egter getoets moet word alvorens aanbevelings in die warmer produksiegebiede gemaak kan word.

Master