Juvenility of apple seedlings: correlation between tree growth habit and flowering index on different apple progenies at the middle west of Santa Catarina State - Brazil.

摘要

Around the World many investigations have already been done to overcome the challenge of the long juvenile period of apple seedlings. To collaborate with apple breeders, a study has been done at Epagri/Cacador Experimental Station in order to investigate the correlation between some parameters of tree growth habit with juvenility phase on apple, expressed as flowering index - FI. After three and a half years from seed germination, a total of 1.287 pre-selections from eight apple progenies grafted on Marubakaido/M-9 inter-stem have been investigated. The following variables were evaluated: (a) plant height - PH; (b) length of the last annual growth of the leader - AGL; (c) length of the internodes - IL; (d) type of leader - TL. Only for TL a reasonable good correlation with FI was observed. There was significant negative correlation between length/thinness of the leader and intensity of blooming on all the eight apple progenies studied. The correlation values varied from R=0,27 for the progeny 'Imperatriz' x 'Fred Hough' to R=0,49 for 'Imperatriz' x M-46/94, 'Imperatriz' x 'Catarina' and 'Imperatriz' x 'Baronesa', with an average value of R=0,44. For all the other variables, the correlation was very poor, even not significant in most cases. For plant height, mentioned in the literature as a good parameter for selecting apple seedlings to shorten juvenile period, not only a very poor correlation with FI was observed, but even some negative correlation between both. The average for all progenies for this parameter was R=0,07 only, being not significant. For internodes length, even showing a negative correlation for all progenies as expected, the correlation values were highly variable. The highest negative correlation was observed for the progeny 'Imperatriz' x M-46/94-R=-0,42 - and the poorest for the progeny M-72/90 x 'Gala'-R=-0,017. These results indicate that for apple progenies grafted on Marubakaido/M-9 inter-stem, the only criterion that offers a certain guarantee for pre-selections leading to a short juvenile period on apple seedlings seems to be the type of leader.