Relationships between seed yield and yield components in common vetch (Vicia sativa ssp. sativa) populations sown in spring and autumn in central Turkey Hu ¨ seyin Kansur Fırıncıog ˘lu a,1, *, Sabahaddin U ¨ nal a , Eraslan Erbektas ¸ a,1 , Levent Dog ˘ruyol b a Department of Forage and Pasture, Central Research Institute for the Field Crops, Yenimahalle, Ankara, Turkey b Agricultural Production Development General Directorate, Department of Plant Production, Ankara, Turkey 1. Introduction Increased feed requirements for the expanding Turkish livestock population necessitate the introduction of forage legumes into crop rotations (Fırıncıog ˘lu et al., 2007). Common vetch (Vicia sativa ssp. sativa) is one of the most important annual forage legumes in Mediterranean-type environments because of its multiple uses (i.e. hay, grain, straw, silage and green manure), its high nutritional value, and its ability to grow over a wide range of climatic and soil conditions (Fırıncıog ˘lu et al., 2009). Furthermore, common vetch fixes nitrogen and thus contributes to soil fertility in rotations. It is estimated that 320,000 ha of common vetch are grown in Turkey (Anonymous, 2006). Most of it is grown for straw and seed in the Central Turkey (CT) where it is reproductive (Ac ¸ıkgo ¨ z, 1988; Fırıncıog ˘lu, 2006). It is sown in spring, but frequent droughts cause crop failures. An initial study showed that, if successful, autumn-sown vetches had the potential for high yield (Fırıncıog ˘lu et al., 1997, 2009). However, death in winter is a major problem in regions with a continental climate (Ac ¸ıkgo ¨ z, 1982; Fırıncıog ˘lu et al., 2009) and the lack of cold- tolerant varieties means that autumn planting may not be feasible. Variety development strategies might be improved by gaining knowledge on the yield component responses to both sowing times for stable and higher yield. Moreover, knowledge of associations between grain yield and its components under rainfed conditions would enhance the efficiency of cultivar development by identifying appropriate characters for selecting superior vetch genotypes. In most species, grain yield is influenced by several characters that affect plant growth throughout the cropping season. Analysis of yield components can help to explain how yield losses occur (Gardner et al., 1985). On the other hand, attempts to increase yield by increasing seed number or seed mass have been somewhat unsuccessful due to the compensation effect that occurs between Field Crops Research 116 (2010) 30–37 ARTICLE INFO Article history: Received 21 July 2009 Received in revised form 10 November 2009 Accepted 10 November 2009 Keywords: Biomass Biomass and seed growth rates Earliness Harvest index Multi-statistical procedures Winter hardiness ABSTRACT In order to investigate the effect of two growing seasons on seed yield, to provide a hypothetical basis to demonstrate the relations of the main agronomic characters and their influences with vetch seed yield, 20 genotypes were grown at two sowing dates, replicated over two seasons at the Research Farm of the Central Research Institute for Field Crops near Ankara in 2001–2004. Fifteen plant characters were measured: seed yield, days to flowering, days to harvest, days to physiological maturity, stem length, number of stems, number of pods, pod length, number of seed per pod, 1000-seed weight, harvest index, biomass, biomass growth rate, seed growth rate and winter death. Results were analysed by multiple statistical analysis: analysis of variance, simple correlation, factor analysis, principle component analysis, path analysis and cluster analyses. Vetch growth and development were strongly affected by sowing in spring or autumn. Though seed-filling period and 1000-seed weight were significantly higher in autumn vetch than in spring vetch, spring vetch produced higher biomass and seed yield. Winter damage severely reduced yield in autumn vetch, and in the absence of winter hardy varieties spring planting must be preferred. The dependence of seed yield on days to harvest, biomass, and biomass and seed growth rates were common to both planting seasons. In spring-sown crops, seed yield also depended on days to physiological maturity, and in autumn-sown crops seed yield depended on harvest index. Faster seed filling had a stronger effect on seed yield than did early flowering. Therefore, early maturity, combined with rapid dry matter accumulation, was expressed as a high biomass, which laid the potential for a greater seed yield. In conclusion, the traits of most interest when selecting common vetch plants to improve seed yield under cold and drought stress conditions are early harvest with faster seed filling and high biomass with higher biomass growth rate. ß 2009 Elsevier B.V. All rights reserved. * Corresponding author at: 2. Cadde No: 34-4, 06500, Bahcelievler, Ankara, Turkey. Tel.: +90 312 2158875. E-mail address: huseyinfirincioglu@ttmail.com (H.K. Fırıncıog ˘lu). 1 Retired. Contents lists available at ScienceDirect Field Crops Research journal homepage: www.elsevier.com/locate/fcr 0378-4290/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.fcr.2009.11.005