Proline accumulation and drought resistance
Ever since the work of Palfi (1968), Singh et al. (1972) and Stewart et al. (1972) attempts were made to associate proline accumulation under drought stress with plant drought resistance. Besides some evidence of proline as a protective molecule of certain proteins, storage of protein breakdown or its minor effect on osmotic adjustment it could never be taken seriously as a marker of drought resistance in breeding and selection work. Even attempted proof of its significance in an empirical correlative manner was not convincing. One of the reasons for failures is represented in the recent publication by Mwadzingeni et al. (2016) which demonstrates the repeated error in protocol of such studies.
They tested Ninety-six diverse wheat genotypes over several drought stress environments for yield and its components as an expression of resistance, as well as proline accumulation in leaves. What ever conclusions they draw about proline as a “marker” for drought resistance is immaterial because of the following failure in the protocol. Proline accumulation is very tightly linked to leaf water status. In this work leaf water status was not measured and proline content was not normalized for leaf water status. Most likely genotypes under stress varied for their leaf water status and thus proline was a function of the phenotypic variation in plant water status rather than genetic regulation, which does not permit the conclusion of its being a “marker” in selection work. This paper is already represented in networks such as NIH, PUBMEDCENTRAL.CA, EOUROPEPMC.ORG, RESEARCHGATE.NET, and SEMANTICSCHOLAR.ORG and it might be taken at face value by most students and their professors.
Amazingly such errors are being repeated since the 1970’s, without creating their tiresome list here.
Mwadzingeni L, Shimelis H, Tesfay S, Tsilo TJ. 2016. Screening of Bread Wheat Genotypes for Drought Tolerance Using Phenotypic and Proline Analyses. Front Plant Sci. 2016 Aug 25;7:1276. doi: 10.3389/fpls.2016.01276.