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Massey University (2013)

Drought resistance mechanisms in "Mediterranean" perennial ryegrass (Lolium perenne L.) and potential for introgression of "Mediterranean" germplasm into New Zealand commercial cultivars

Hussain, Sajjad

Titre : Drought resistance mechanisms in "Mediterranean" perennial ryegrass (Lolium perenne L.) and potential for introgression of "Mediterranean" germplasm into New Zealand commercial cultivars

Auteur : Hussain, Sajjad

Université de soutenance : Massey University

Grade : Doctor of Philosophy in Plant Science (2013)

Résumé partiel
The unique topography of New Zealand creates a wide variation in rainfall and temperature between and within the two islands of the country. As a result, successful use of perennial ryegrass (Lolium perenne L.), the backbone of New Zealand’s agricultural economy, has been restricted to only the higher rainfall and cooler areas of the country. However, there has been only limited analysis of drought resistance in forage grasses at the trait level. This PhD study was conducted on a perennial ryegrass cultivar “Medea” developed in Adelaide in the 1960’s from reportedly drought resistant and summer dormant germplasm of North African origin. The main objectives of the study were to compare Medea with a high yielding but drought susceptible current New Zealand cultivar, Grasslands Samson for their drought resistance potential and to evaluate Medea for its suitability for introgression with Grasslands Samson, in a plant improvement programme. Drought resistance strategies of Tolosa, Matrix and Ceres One50 were also evaluated. In total six glasshouse experiments were conducted. Experiment 1 (April – September 2008) compared winter vegetative growth of potted plants of Grasslands Samson and Medea. Yield of Medea was <50% that of Grasslands Samson, but glasshouse temperature at times exceeded 25°C, so it is possible that this temperature was high enough to partially trigger summer dormancy in Medea. In Experiment 2 (summer 2008 – 2009) techniques for assessing drought resistance were developed, and in Experiment 2 and Experiment 5 (summer 2009 – 2010) drought resistance strategies exhibited by individual cultivars were evaluated. Experiment 2 included Medea, Grasslands Samson, an unreleased tetraploid breeding line developed from Grasslands Samson and Tolosa. Experiment 5 evaluated Matrix and Ceres One50, in addition to Grasslands Samson and Medea. Drought resistance strategies observed in Medea included deep rootedness and high leaf proline contents, but there was some evidence for lack of transpiration reduction in water deficit stress. Medea had prolific flowering. Grasslands Samson and its tetraploid were more productive than Medea in these experiments. However, Tolosa produced the same shoot DW as Grasslands Samson with greater retention of soil moisture, indicating higher water use efficiency. Experiment 3 (March 2009 – February 2010) compared five family groups, each comprising a Grasslands Samson and a Medea parent, and three of their F1 progeny. In this experiment plants were 11 months old when root traits were evaluated and for these older plants, Grasslands Samson had a higher root to shoot ratio and deep rootedness than Medea. Medea plants had similar shoot DW to Grasslands Samson plants during winter, but 46% lower shoot DW in summer.

Mots clés : Perennial ryegrass ; Lolium perenne ; Ryegrass drought resistance ; Plant-water relationships

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Page publiée le 21 septembre 2013, mise à jour le 7 août 2017