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The main goals of the wheat androgenesis experiment were to study the main phenomena of in vitro androgenesis in anther culture of Fj populations (10) and their parents (6), to compare the usage of P-4 and G-17 media for the formation of embryo/callus and to demonstrate a new plant regeneration system.The P-4 induction medium was found to be significantly better than the G-17 in the number of responsive anthers (RA) and calli induced (GI) at the 1 % and 0.1 % level, respectively. Genotypic effect was evident in both RA and GI. The yields of F2 populations in RA and GI were significantly higher than those of their parents regarding both media. The data confirmed the existence of heterosis for RA and GI in F2 populations.The ratio of green/albino plant regeneration was more favourable in the G-17 derived embryo/calli than in the P-4 derived ones.The frequency of plantlet regeneration was enhanced in the group of unresponsive calli by the application of the multiple-step regeneration system. In this system the calli lacking well developed morphogenic structure were transferred to a new regeneration medium, containing a higher concentration of the same cytokinin, other cytokinin or basic medium, before the occurrence of irreversible changes in their physiology.

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In order to update phosphorus (P) fertiliser recommendations for the Finnish clay and loam soils enriched with applied P, the effects of repeated P fertilisation on the yields of cereal and other crops were measured at eight sites over a period of 12−18 years. Yield results of some earlier field studies were also used in calibrating the soil test P values determined by the Finnish acid ammonium acetate method (P Ac ). Significant yield responses to P fertilisation were obtained on soils which had low P Ac values or medium levels of P Ac and too low or too high pH values (< 6.0 or 7.5 in water suspension). The mean relative control yield (RCY, yield without applied P divided by yield with sufficient P multiplied by 100) of the eight sites was 94.6% (n = 128, mean P Ac 15.5 mg dm -3 ) varying from 87% at P Ac 2.8 mg dm -3 to 100% at high P Ac . A P Ac level of 5−7 mg dm -3 was adequate for cereals, grasses and oilseed rape on the basis of the RCY value of 95% at optimal pH. At this P Ac replacing the amounts of P in the crops (14 kg in 4 t grain) and the fixation of extractable P (about 6 kg ha -1 a -1 ) produced almost maximum yields in favourable seasons and were considered optimal.

Each crop variety has a genotype-specific ability to maintain performance over a wide range of environmental conditions. This ability is usually referred to as the sensitivity or adaptability of a variety. Such an ability is an important property, because farmers naturally want to use varieties which perform well in their own fields. Assessing sensitivity has, however, proved difficult, because of problems involved in defining and measuring the wide diversity of natural environments. These problems often lead to split statistical analyses of trial data or statistical models including explanatory variables with no biological interpretation. That causes ambiguity in statistical inference and prediction. The present study shows how the latest advances in statistical research can be applied to overcome some of these difficulties. A key point is to use the conditional expectation of the yield given the environment as a latent explanatory variable. In this way the predicted yields of different varieties can be estimated at any expected environmental yield level. Discussion is restricted to yield data but similar methods can be applied to other performance characters. The Finnish statutory variety trial data are used to illustrate the methods and the results.