Evaluation of faba bean breeding lines under different rainfed conditions

Drought is one of the major factors limiting faba bean (Vicia faba L.) production in Mediterranean region with irregular water distribution and moisture level below than 500 mm. A major objective of any breeding program in this region is to develop drought-tolerant/resistant genotypes of faba bean that are well adapted to a wide range of environments, since environmental variation causes differential genotypic responses. The objective of this study was to evaluate the response of eight faba bean drought tolerant breeding lines - selected in Tel Hadya (Syria) with moisture level below 300 mm - and three cultivars under rainfed conditions in two stations (Terbol and Kfardan) of the International Center for Agricultural Research in the Dry Areas (ICARDA) representing two different agro-climatic zones in Bekaa, Lebanon during 2008/2009 cropping season. The breeding lines were compared in terms of growth vigor, yield, yield components, harvest index and water use efficiency in both locations. The seasonal accumulated rainfall in Kfardan station (289 mm) was 42% less than that recorded in Terbol station (501 mm). Genotypic variations for several yield characters were recorded in both locations. Plant height, number of nods per plant, number of lateral branches and internodes’ length were higher in Terbol by 14%, 50%, 25% and 48%, respectively, than those recorded in Kfardan. Highest grain yields were recorded in Terbol station by the genotypes ILB1814 (Syrian local large) and ILB1266 (Aguadolce), followed by DT/B7 9013, ILB 1270 Reina Blanca and DT/B7 9005. Similarly in Kfardan, the genotype DT/B7 9013 had the highest grain yield, followed by ILB 1814 (Syrian local large), DT/B7 9005, DT/B7 9043 and ILB 1266 (Aguadolce). The biological yield, total biomass, grain yield, harvest index, number of pods per plant and the number of seeds per plant recorded in Terbol were higher by 39%, 16%, 77%, 30%, 54%, and 53%, respectively, than those recorded in Kfardan. This means lines yielding good under low rainfall area may not perform well under high rainfall environments. The biomass water use efficiency (WUEb) ranged from 0.4 to 0.61 kg m-3 in Terbol and from 0.63 to 0.89 kg m-3 in Kfardan, whereas the grain water use efficiency (WUEg) ranged from 0.32 to 0.61 kg m-3 in Terbol and from 0.36 to 0.55 kg m-3 in Kfardan. The WUEb was significantly higher (by 50%) in kfardan than in Terbol whereas the WUEg in Kfardan was significantly lower (by 8%) than that in Terbol. Thus it seems that the remobilization of assimilates is limited in Kfardan due to the severe terminal drought