Effects of sowing times on seed yield, protein and galactomannans content of four varieties of guar (Cyamopsis tetragonoloba L.) in a Mediterranean environment

Guar (Cyamopsis tetragonoloba L.) is a summer, annual, legume crop primarily grown as an industrial crop for the galactomannans content of its seeds. Guar is grown in India, Pakistan and USA, but no cultivation has of yet been established in a Mediterranean environment. In the last few years, world demand for guar gum has considerably grown and its price has increased. In order to explore the possibility of extending guar cultivation into a Mediterranean environment, a 2-year experiment was carried out in Southern Italy with the aim of evaluating the seed yield, protein and galactomannan content as affected by two sowing times (early and late) and four different varieties. Guar seed was produced with an average of 2.650 m3 ha−1 of water, which is a volume compatible with many semiarid areas. Lewis and Santa Cruz cultivars proved to be the most productive varieties (2.5 t ha−1) and the early sowing time resulted in higher yields compared to the later one (2.3 t ha−1 vs. 2.1 t ha−1). Protein content was variable among varieties and galactomannan content was higher in the second sowing time, the highest protein and gum yield was obtained in the early sowing due to higher seed yield by Lewis and Santa Cruz. Galactomannans yield was mainly related to pods per plant and seed yield, thus management techniques and genetic improvement of guar for gum production should be addressed to maximize the number of pods per plant. In general, guar seed and gum yield support the hypothesis that the Southern European Mediterranean environment is a potentially valuable area for guar cultivation.