Cytogenetic Studies in Poa Pratensis and Its Hybrid With Poa Alpina

N 1933 MUNTZ~NG published his paper on 2Apomictic and sexuaI I seed formation in Pea)) and was the first to demonstrate apomictic seed formation in Poa pratensis.Poa pratensis is one of the most important species of grass in our pastures, and therefore breeding work with this species is of the greatest importance.MUNTZING'S findings had far-reaching effects on this work.It was therefore natural that a n investigation should be made on the occurrence of apomixis in the heeding material of Pocc pratensis 1 had in charge at that time at Weibullsholm.Gradually this material was bp-eatly increased, seeds and plants being collected on journeys or acquired in other ways from Scandinavia, Finland, Germany and England,The main purpose of the investigations was originally to study the occurrence of apomixis in the breeding material, but owing to the results and experiences gradually obtained they came to embrace several other problems.They cannot yet be regarded as concluded.Up to the present the investigations have been mainly concerned with the following problems in Poa prdensis :1 ) Gametophyte and sporophyte development in apomictic and sexual forms.2 ) The occurrence of aberrants in apomictic forms and their inheritance.3) The presence o f apomixis in material froiii different habitats.1 ) Tlic occurrence of polyniorphism and in con junction therewith the niorphology of forms having different chromosome numbers.5 ) The origin of apomixis.6 ) The origin of hybrids with Pocc alpina and their progenies.Some of the results obtained have been published previously (AKERBERG, 1936a(AKERBERG, and b, 1938(AKERBERG, , 1939(AKERBERG, and 1940)).In these papers a special account of methodical quektions is given :)lid is therefore not Hereclilns X X V H I . 2ERIK AKERBERG repeated here.For the same reason no review of other similar investigations in Poa is given in this ))Introduction)).In the following pages the significance of found values has in many cases been tested.To obtain the P-values corresponding to the found variance quotient, x' and t the tables in ,Biologisk variationsanalysr by BONNIER and TEDIN (1940) are used.For the average value the symbol M is used and for the number of variants the symbol n.During the years 1935-1938 the material was cultivated at Weibullsholni, in 1939 at Svalof and Lannas, Undrom, the work being now carried on exclusively at the last-mentioned station.I wish here Lo express my deep gratitude to Prof. H. NILSSON-EHLE, late head of the Swedish Seed Association, who was also my teacher in genetics, to Prof. A. AKERMAN, the present head of the institute, both of whom have in various ways made it possible for me to accomplish my work, and to Dr. G. NILSSON-LEISSNER