5ll. of the root mass in the 7-wk period, but only in a few instances were there statistically significant differences.

Transcription

1 PROPAGATION OF OTTAWA APPLE ROOTSTOCKS BY SOFTWOOD CUTTINGS S. H. NELSON Department of Horticulture Science, (/niverity ofsaskatchewan, Saskatoon, Sask. Received0 Oct. 15, accepted l5 Feb. 16. Can.. Plant Sci. Downloaded from by on 01/06/18 NrlsoN, S. H. 16. Propagation of Ottawa apple rootstocks by softwood cuttings. Can.. Plant Sci. 56: 5ll The difficulty in rooting Ottawa 3 apple (Malus sp. Mill.) rootstock by softwood cuttings under intermittent mist at other locations was not experienced at Saskatoon, Saskatchewan. With the exception of Ottawa 7. which would seem to be slower rooting than the rest of this rooistock series, namely, Ottawa 3, 5, 8, I I and 1, high levels of rootability were obtained with 1.7-cm (5-inch) softwood cuttings under three types of intermittent mist propagation outdoors. The polyethylene tent over the intermittent mist bed was generally superior to the open intermittent bed with bottom heat and it, in turn, superior to the open intermittent mist bed without bottom heat. The use of hormone applications tended to speed up rooting and increased the yield of the root mass in the 7-wk period, but only in a few instances were there statistically significant differences. L'enracinement de boutures herbac6es du porte-greffe de pommier (Malas sp. Mill) Ottawa 3 sous brouillard intermittent n'a pas caus6 de difficult6 b Saskatoon (Sask.), contrairement d ce qu'on avait 6prouv6 I d'autres endroits. A I'exception d'ottawa 7, qui semble avoir pris plus de temps i s'enraciner que le reste de cette s6rie de porte-greffes qui comprend Ottawa 3, 5, 8, 11 et 1, on a obtenu un excellent enracinement d partir de boutures herbac6es de 1.7 cm (5 po) sous trois types de bouturage h I'ext6rieur avec n6bulisation intermittente. L'emploi d'une tente de poly6thyldne sur le lit de bouturage s'est trouv6 sup6rieur au lit ouvert avec chauffage par le bas, lequel s'est montr6 meilleur que le lit ouvert sans chauffage. L'application d'hormones semble avoir acc6l6rer I'enracinement et accru le d6veloppement de la masse racinaire au cours de la p6riode de bouturage de 7 semaines, mais saufde rares cas, les diff6rences n'ont pas 6t6 significatives. The ease of rooting in the routine multipli- had no success with either softwood or cation of small numbers of the Ottawa apple leafbud cuttings under intermittent mist. (Malus sp. Mill.) rootstock series (3,5, 7, Poor rooting by the stooling method, but 8, 1 I and 1) by softwood cuttings in good success by root cuttings has been outdoor intermittent mist beds without reported (Granger and Hogue 14; Hutchbottom heat (Nelson 15) has not been inson 14; Spangelo etal.14). found by other researchers. Because of its Since the original population (Nelson dwarfing ability, particular attention has 15) was not replicated and since intermitbeen given to Ottawa 3 (Spangelo et al. tent mist is an accepted form of propagation 14). They reported relatively poor suc- for many types of horticultural plants, the cess with Ottawa 3 propagated as softwood work was repeated using all available plant cuttings under intermittent mist, while material to test hormone and propagation Granger and Hogue (14) reported that bedeffects. although Ottawa 3 could be propagated by softwood cuttings, the technique was rather MATERIALS AND METHODS difficult. Cumming and Aldwinkle (14) The propagation beds, as described by Nelson can.. ptant Sci. 56:5rr-st5 (uly 16) ( 0), consisted of intermittent mist outdoors 5ll

2 51 CANADIAN OURNAL OF PLANT SCIENCE Can.. Plant Sci. Downloaded from by on 01/06/18 without bottom heat (), intermittent mist outdoors with bottom heat (lead-covered heating cable) at 0 C () and intermittent mist outdoors enclosed in a polyethylene tent (IMO-PT). All beds had removable 1-cm high, clear polyethylene (6-mil) side panels, while the polyethylene tent had the plastic permanently affixed to the roof and gables as well. The mist interval was approximately l5 sec every 3 min. Twenty stools of each rootstock (established in an unshaded area in 1 aod cut back to ground level annually in the spring since 13) were available. The cuttings from these unmounded stools were taken as soon as the regrowth exceeded l3 cm on most ofthe shoots. The shoots were not harvested until 3 uly 15 because of a late season, and were trimmed in bunches in a mitre box without regard to node to give I.7-cm (5-inch) cuttings. The basal leaves were removed approximately half way up the stem and the cuttings, as well as an untreated control, were treated with commercial preparations (Seradix) containing 0.1,0.3, and 0.87c IBA in talc. The number of randomlv olaced replications in the propagation bed and the propagation beds selected (Table l) was governed partly by the number of cuttings and partly by the space avallable in the propagation beds. With the exception of Ottawa 7 where l0 cuttings per replicate were used, the rest of the replicates contained l cuttings. After 7 wk the cuttings were lifted and scored (Fig. l) before they were transplanted' Both the percentage rooting and the average score of the rooted cuttings were subjected to either analysis of variance or unpaired / tests. RESULTS AND DISCUSSION In general, the rooting was considered good and the cuttings remained in excellent condition. Although the rooting performance of the individual rootstocks varied (Table l) and will be discussed separately, there was generally no significant effect on rooting percentages from the various propagation methods or hormone treatments. Where comparisons could be made, how- Fig. I. Example of root masses used to score Ottawa 3 apple rootstock: (left to right) l, very light;,-light;3, medium; 4, heavy; and 5, very heavy. Similar root masses were used to score the other rootstocks.

3 NELSON-PROPAGATION OF OTTAWA APPLE ROOTSTOCKS 5 13 Table 1. Average rooting percenrages of the Ottawa apple rootstock selections propagated under intermittent mist outdoors Ottawa rootstock selection Propagationt frame Number of replications I.B.A. hormone treatment O.l7o 0.37o O.87o Can.. Plant Sci. Downloaded from by on 01/06/ ll 8 t IMO-PT IMO-PT IMO-PT z 1, Intermittent mist outdoors, no bottom heat;, Intermittent mist outdoors, bottom heat 0 C; IMO-PT, Intermittent mist outdoors, polyethylene tent. Note: Very light rooting (score 1) scores were not included in the above percentages. ever, the cuttings had a greater average rooting score in the IMO-PT treatments than the treatments (Table ). Similarly, the cuttings in rhe treatments had a greater root score than those in the treatments. Some rootstocks had a significantly higher root mass as a result of hormone treatment. These results are very similar to those obtained by the author with the juvenile stage of the apple rootstockmalus robusta l r00 and other unnamed rootstock selections in numerous unpublished results at Ottawa in the late 1950's. In those studies the usual effect of either bottom heat or the polyethylene tent was a speeding up of the rooting process resulting in a greater root mass. The effects were generally not additive and the beneficial effects of hormone applications were more likely to be expressed in propagation frames considered to be less efficient. i.e... Table. Average root score of the Ottawa apple rootstock selections propagated under intermittent mist outdoors Ottawa rootstock selection ) ll 8 1 Propagationt frame IMO.PT IMO.PT IMO.trl Number of replications 3 z z 3. l l O LB.A. hormone treatment O.lVo O.3Vo 0.8Vo O O 4.6.Z.4.) t, Intermittent mist outdoors, no bottom heat;, Intermittent mist outdoors, bottom heat 0 C; IMO-PT, Intermittent mist outdoors, polyethylene tent. *Root scores : l, very light;, light; 3, medium; 4, heavy ; and 5, very heavy.

4 514 CANADIAN OURNAL OF PLANT SCIENCE Can.. Plant Sci. Downloaded from by on 01/06/18 Ottawa3(RobinxM.9) Good rooting was obtained even though this rootstock was only tested in the propagation bed. The rooting percentages were not significantly different in the various hormone treatments, but the root masses on the hormone treatments, although not significantly different among themselves were significantly greater than the control (LSD:.01 level, 0.846;.05 level, 0.559). The average root mass was the highest encountered in the study. In all, only 9 of the 144 cuttings failed to have a root score of. The condition of the cuttings, except for four that rotted in one replicate of the 0.87o IBA treatment, was excellent. From these results by a propagation method considered the least efficient of those tested, it is apparent that this rootstock should not be difficult to root under intermittent mist, although the application of a mild hormone will speed up rooting and increase the root mass. Ottawa 5 (M. bsccata O.P.) This is another selection that rooted readily with all but I (unaccounted) cutting out of 19 attaining a root score of. Although there was apparently earlier rooting from both the use of the polyethylene tent and hormones, the data were not significantly different. Ottawa 7 (M. baccata O.P.) Considering the other selections and their response to the propagation techniques, this selection is probably the most difficult selection to root. Better percentages and higher root masses could have been anticipated under the polyethylene tent and intermittent mist. Hormone applications did not significantly affect the root mass. The variety is obviously a slower rooter than others, but the cuttings that had not attained a root score of were still in excellent condition and still had the potential to root or develop b tter roots had the period been longer. Ottawa 8 (M. baccata var. gracilis x M.7) This is another rootstock with a high rooting potential that responded to propagation treatment. The rooting in the bottom heat treatment () was statistically significant (.01 level) over that received from the treatment both for percentage rooting (root score and over) and for average root mass. The application of hormone had no significant effect on the root mass of the rooted cuttings. Ottawa ll (M. robusta 5 O.P.) Obviously, this selection is easier to root than Ottawa 8 with only 5 of 40 cuttings not attaining a root score of. There was no significant difference in percentage rooting between the treatments, but the root mass was statistically greater (5%o level only) in the treatment. Although this selection was apparently inherently easy to root, it did respond significantly to hormone treatment, with the response being more noticeable where no bottom heat was used. (LSD:.01 level, 0.715;.05 level, 0.-?89). With bottom heat, the response was less with only the two stronger concentrations being significant (.05 level) over the untreated control. Obviously this selection does respond to hormone treatment with earlier rooting. Ottawa 1 (Robin x M.9) Except for one cutting (unaccounted), all cuttings attained a root score of with this relatively easy-to-root clone. The use of the IMO-PT propagation techniques was superior (.01 level) to the treatment in average root mass, but the use of hormones, although apparently increasing root mass, was not statistically significant. DISCUSSION With the possible exception of Ottawa.7, this series of rootstocks has a very high rooting potential using softwood cuttings under intermittent mist, and performed as well as M. robusta 5 being rooted for

5 NELSON-PROPACATION OF OTTAWA APPLE ROOTSTOCKS 5r5 Can.. Plant Sci. Downloaded from by on 01/06/18 routine increase in the beds at the same time. As long as the juvenile stage (Blair et al. 1956) is maintained, they should present no rooting problem. It is essential, however, that the crowns of the stools be maintained as close to ground level as possible. Rootability of juvenile stools of Malus robusta 5 apple rootstock showed a severe decline even when the crowns were pruned to 6 inches instead of ground level (Nelson 11, unpublished data). It is difficult to explain the poor rooting of softwood cuttings obtained by the other researchers in this rootstock series, _but the possibility of tissue with declined iuvenilitv being perpetuated, allowing the "to*n, on the stock plants to become too elevated, and taking the cuttings too late are all considerations. ACKNOWLEDGMENTS The information on the parentages of these rootstocks supplied by R. L. Granger and G. Rousselle, Research Station, St. ean, euebec is gratefully acknowledged. BLAIR, D. S., MACARTHUR, MARy and NELSON, S. H Studies in the srowth phases of fruit trees. Proc. Amer. Stc. frortic. Sci.65: 75-'79. CUMMING,. N. and ALDWINKLE, H. S Apple rootstocks for colder climates. Fruit Var. Hortic. Dig. 8(l): HUTCHINSON, A. 14. Apple rootsrocks. Ont. Min. Agric. and Food Fact Sheet pp.l-4. GRANGER, R. L. and HOGUE. E Propagating apple rootstocks by root cuttings. Agric. Can. Tech. Bull pp. l-6. NELSON, S. H. 10. Mist beds for rootins cuttings. Can. Dep. Agric. Publ. I 103, I I pp. NELSON, S. H. 15. Report of Fruit Commif tee, Proc. West. Can. Soc. Hortic. 31: 65a-65b. SPANGELO, L. P. S.. FEER. S. O.. LEUTY, S.. and GRANGER, R. L. 14. Ottawa 3 clonal apple rootstock. Can.. Plant Sci. 54:

6 Can.. Plant Sci. Downloaded from by on 01/06/18 This article has been cited by: 1.. B. Taylor The selection of Aotea apple rootstocks for resistance to woolly aphis and to root canker, a decline and replant disease caused by basidiomycete fungi. New Zealand ournal of Agricultural Research 4:3-4, [Crossref]