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SUMMARYThe number of replications and locations used in a cultivar evaluation scheme is an important factor affecting the trial heritability (H) and optimum resource allocation. The aim of the present study was to calculate the required number of replications and locations for realizing an optimumHof 0·75 and to identify the most effective test locations for cotton (Gossypium hirsutumL.) in Greece. The data for lint yield, plant height, verticillium wilt (Verticillium dahliaeKleb.) and fibre quality were derived from an 8-year experiment (2000–2007) conducted under irrigated, Mediterranean conditions at 14 locations along the Greek mega-environment. Analysis of variance was performed to calculateHas well as genotype plus genotype × environment (GGE) biplot analysis to determine the location's desirability. It was determined that the four replications currently used in the evaluation of lint yield were sufficient, whereas four locations were proposed as optimum in lieu of the current 8–14 locations used in the evaluation. Two locations excelled as the most effective for lint yield evaluation and one for selection of genotypes tolerant to verticillium wilt using as criteria: the high and consistent across yearsH(0·75), GGE biplot representativeness and discriminating ability. Moreover, one location was selected as a backup based on average trial failures. Plant height was sufficiently evaluated by four replications and two locations, while verticillium required four replications for realizing lowerH(0·60) and three locations for even lowerH(0·40). Regarding quality, an increase of replications from the two currently used to four was sufficient for evaluation of all the traits. The advantage of reducing the number of locations for evaluation of lint yield to just four casts no doubt on the evaluation precision of lint percentage, length, strength and elongation but does for micronaire, short fibre index and uniformity, which realized lowerH(0·60 or 0·50).

SUMMARYWinter rapeseed was introduced into Greece a decade ago to provide oil for biodiesel. To identify agronomic traits affecting yield and quality, three hybrids and an inbred line were tested over two seasons (2005–2006 and 2006–2007) and four locations, in central and northern Greece, varying in pedo-climatic conditions. The large variations in seed yield, quality and agronomic traits were largely ascribed to location; in contrast, cultivar accounted for ⩽0·010 of the variation for many traits. Below 40°N, rapeseed is a risky crop; short season, high temperatures and low rainfall during reproductive growth diminished seed yield and oil content, increased oleic and erucic acid and minimized linolenic acid. A hybrid, Exact, with tall stature and large seeds was adaptive to such conditions. The most productive location had dense stands with tall plants bearing numerous pods on the main raceme. At the site with the coldest winter, plant density (PD) was lowest (ca. 30 plants/m2) but rapeseed compensated by producing large seeds, with high oil content and harvest index (HI). A biplot revealed that the hybrid Excalibur, outperforming the other cultivars for oil content in six out of eight trials, produced the highest and most stable oil yield. Combined data showed that seed yield and oil yield were positively correlated with PD, seed size and HI and negatively to the number of pods on branches and per plant. Large seeds had high seed oil content. Oleic acid was negatively correlated to linolenic acid concentration. High temperatures and low rainfall favoured oleic acid, which was positively associated with seed number per pod.

Cultivar mixtures are suggested for low-input farming systems because they introduce functional diversity. The lack of common vetch (Vicia sativa L.) cultivars bred for and adapted to low-input farming systems raises the issue of whether the mixtures composed from varieties developed under conventional conditions can satisfy the demands of low-input agriculture. The objective of this project was to evaluate the performance of fi ve common vetch varieties and mixtures of these varieties in a low-input system. Three-year preliminary experiments were conducted among widely adapted cultivars bred under high-input conditions to select the most productive cultivars. Thus, fi ve common vetch cultivars and their mixtures were evaluated under low-input farming system (2007–2009). Dry matter (DM) production and crude protein content were measured for each entry. Mixture effect (ME) was calculated to measure the relative performance of a mixture over its components. Genotype main effect plus genotype × environment interaction (GGE) biplot analysis was used to assess yield and stability. It was observed that ME for DM was positive for three mixtures over environments and ranged from 0.19 to 4.63 Mg ha −1 . GGE biplot analysis indicated that two of the previous three mixtures exhibited the greatest yield and stability. Crude protein values of the mixtures were at least comparable with their individual cultivar components. These results showed considerable advantages of mixing common vetch cultivars bred under high-input conditions for use in low-input farming system.