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Accueil du site → Master → Afrique du Sud → 1998 → Determination of drought tolerance in nineteen Vigna unguiculata cultivars and breeding lines using four reliable screening methods

University of the Witwatersrand (1998)

Determination of drought tolerance in nineteen Vigna unguiculata cultivars and breeding lines using four reliable screening methods

Laurie RN

Titre : Determination of drought tolerance in nineteen Vigna unguiculata cultivars and breeding lines using four reliable screening methods

Auteur : Laurie RN

Université de soutenance : University of the Witwatersrand

Grade : Master of Science MSc (Genetics) 1998

Résumé
Cowpeas (Vigna unguiculata) is indigenous to Africa and is utilized by the African population in times predating the colonial era. It is known that cowpeas are drought tolerant but variation exists. In order to identify tolerance or sensitivity early in a breeding programme it is of importance to be able to make use of laboratory screening methods in an attempt to shorten delays in the selection in the breeding programme. Nineteen cowpea cultivars and breeding lines, selected on importance, were grown in a greenhouse in two different seasons, winter and summer. Drought stress was induced 50 days after planting by withholding water. Drought tolerance was determined by using free proline concentrations, chlorophyll fluorescence, polyamine concentrations and 2,3,5-triphenyltetrazolium chloride (TTC) reduction as screening methods. Free proline concentrations were measured at weekly intervals in drought stressed and watered plants. Results showed that proline accumulates during drought stress and that differences between the cultivars and breeding lines could be detected. Chlorophyll parameters, minimal fluorescence (Fo), photochemical maximum (Fm) and quantum efficiency of photo system II (Fv/Fm) were used to determine drought tolerance. Tolerance and sensitivity could be measured as well as differences between the cultivars and breeding lines. The use of polyamine concentrations in determining drought tolerance in cowpeas was not very successful. Low yields of polyamines were obtained and poor correlation found between polyamine levels and drought tolerance. In the 2,3,5-triphenyltetrazolium chloride reduction experiments, leaf discs were subjected to simulated drought stress using 0.5M mannitol as a mild stress and 1M mannitol as a severe stress. From this the cultivars and breeding lines could be ranked in their susceptibility and tolerance to the stress. Unpublished data obtained from a greenhouse experiment (Appendix B) were compared with the results of the screening methods. From the four screening methods, the results of three, free proline concentrations, chlorophyll fluorescence and 2,3,5-triphenyltatrazolium chloride assays, correlated well with the results of a greenhouse experiment

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Page publiée le 14 octobre 2017