Genotypic Variation Of Phosphorus Use Efficiency Among Moroccan Faba Bean Varieties (Vicia Faba Major) Under Rainfed Conditions

Abstract

Faba bean (Vicia faba L.) is one of the most important food legumes grown in Morocco under rainfed conditions. This crop requires phosphorus (P) fertilizers to produce higher yields. However, many farmers use low quantities of P because of its cost and the risk of drought. Consequently, the use of varieties with high P use efficiency (PUE) can improve productivity and farmers' income under erratic conditions where the application of high amounts of P is not economically justified. The genetic variation of PUE among Moroccan faba bean varieties was studied under different levels of available phosphorus to orientate the choice of adapted varieties. Two experiments were conducted, under rainfed conditions, at the experiment station of Douyet (Morroco) in 2000-2001 (year 1) and 2002-2003 (year 2). In both years, four P treatments 0, 40, 80 and 120 kg P2O5 ha(-1) as fertilizer and four faba bean varieties (G) were tested. In year 1, the varieties tested were Aguadulce, Defes, Karabiga and Lobab. The same varieties were used in year 2 with the exception of Aguadulce, which was replaced by a determinate genotype with smaller straw production. Results showed that the G effect on PUE was significant in year 1, but not in year 2. In the conditions of the moderate P availability (year 1), the variety Defes had the highest PUE and grain yield. Where P availability was lower (year 2), the highest PUE was reached by Karabiga; however, the difference with Defes was not significant. Data showed also that PUE was positively correlated with harvest index (HI) and phosphorus harvest index (PHI). In year 1, genotypic variation for PUE was mainly explained by phosphorus utilization efficiency; but not by phosphorus uptake efficiency. From this study, we can conclude that for rainfed conditions, the breeding strategy is to develop genotypes like Defes with high HI and improved PUE.