WHAT MAY BE THE BASIC REASON(S) FOR GENOT YPE-DEPENDENT RESPONSES TO PLANT-DENSITY

The genotype dependent plant density response for maize (Zea mays L.) is well known. At the same time the traditional field trial method for evaluating this feature is not suitable as a fast, cheap screening me thod, not to mention the improvement of the gene pool for plant densit y tolerance. A new method is thus required which can be used for both purpose, i.e. it must be fast, cheap and independent of changes in the sink-source relationship. The response in biochemical feature(s) coul d be suitable for this purpose. In order to discover such features(s), the basic reason for genotype dependent plant density responses were investigated, based partly on the findings of the last 30 years, and p artly on the results of shading experiments carried out in Keszthely. Plant density tolerant and sensitive hybrids differed in their light r equirements. So the yield decrease as a response to same shading was s ignificantly less in the tolerant hybrid than in the sensitive one. Co nsequently, shading provided a good model of the plant density effect. Since the yield is not a suitable feature for breeding purposes (with hand pollination it is impossible to achieve 100% seed set), an attem pt was made to find biochemical propert/y/ies. In the first step the c hlorophyll concentration, including cholorophyll A and B and the ratio of A, B was investigated. The differences in chlorophyll were minor a nd inconsistent, so this was not a suitable feature for demonstrating the shading effect. For the further research strategy suitable biochem ical propert/y/ies must be found. Since the light does not cost money, this is the key to improve the grain yield without extra expenses.