Variation Among Alnus Progenies Grown in OHIO

Materials and Methods

Seed from 12 provenances of European black alder and one provenance of Italian alder were received in December 1979 from Dr. Richard B. Hall, Iowa State University, Ames, Iowa. Seed were stratified in moist sand at 2°C for four months before planting in flats in the greenhouse. Seedlings were grown for one month in these flats, then inoculated with 800 ml/flat of a slurry containing nitrogen-fixing Frankia (Strain ASN1) donated by Dr. Maurice Lelonde (Charles F. Kettering Research Laboratory, Yellow Springs, Ohio). His methodology for slurry preparation and inoculation (11) was followed closely. After inoculation, the soil surface was kept fully moistened for 48 hours.

Several weeks later, seedlings were transplanted to 8 x 8 x 28 cm decomposable, cardboard containers and placed outside for further growth and eventual overwintering. In April, 1980, these seedlings were transplanted to a field site of silt loam soil near Delaware, Ohio (Fig. 1). A randomized complete block, split-plot design was used, with seedlings from each provenance planted together as a “major” plot in each of 5 blocks; open-pollinated families (one family = seedlings grown from seed collected from one tree) within provenances formed cohesive “minor” plots, and varied in number from one to three families per provenance, with three being most common. Depending on availability, from 9 to 12 trees per provenance were planted in each of the 5 blocks.

• Download figure
• Open in new tab
• Download powerpoint

Figure 1.

The alder plantation near Delaware, Ohio in 1993.

Data on injury from European alder leaf miner (Fenνsa dohrnii) were collected in August, 1983. For these data, a visual estimate was made of the percentage of each tree’s total foliage showing leaf miner injury. Winter dieback data were collected by estimating the percentage of the entire length of each tree’s central leader showing winter injury. This was recorded in June of 1983 and June of 1984. Earliness of growth initiation, or “flushing”, recorded in early May, 1984, was based on an index of leaf development and growth from 0 = very late to 100 = very early. Heights (cm) and diameters (mm) 1.4 m above the ground were measured in the autumn of 1987 and 1992, respectively.

Percentage data initially were analyzed using the arcsìn transformation. When the data were analyzed subsequently as actual percentages, there was very little difference in the results as compared to the arcsin transformed analyses. Therefore, we chose to present the results as percentages in order to preserve the original units of measurement. All statistical analyses were done using the SAS statistical package (14). Mean separation was performed using the least significant difference (Isd) test at the 5%level of significance.

Results and Discussion

Provenances varied significantly in all traits measured. Significant variation among families within provenances occurred only with time of flushing, however. (Copies of detailed results of statistical analyses are available by request from the authors). The fastest growing trees in height were from former West Germany, France, Denmark, and former Yugoslavia; the slowest growing were from seedlots collected from Iran and parts of southern Europe (Spain, Italy, Bulgaria) (Table 1). It should be noted that seedlings from Iran showed extensive winter dieback of the central leader and might be expected to show less cumulative height growth. Ranking of progenies in diameter growth, measured in 1992, generally followed the same general pattern shown in 1987 for height: Seedlings from Yugoslavia, Denmark, France, and West Germany again were among the largest and those from Iran, Scotland, Spain, and Italy were the smallest.

The Italian alder showed the least leafminer damage, although variation among the other provenances was quite pronounced, following no apparent geographic trend. This is the first report of such large variability in insect resistance in alder; significant gains in resistance possibly could be made with a well-designed breeding program involving crosses within and between both Italian and European black alder (Table 1).

Most of the trees of Italian alder and of European black alder from Iran suffered severely from winter injury and both showed poor survival, with less than 14 percent of the Italian alder and only 42 percent of the Iranian black alder surviving in 1987 (Table 1). Survival in 1992 was lower still; only 7 percent of Italian and 33 percent of Iranian alder survived. Trees from other provenances showed excellent survival and little winter dieback. Hall and Miller (9) also found that trees from near the Mediterranean, Black, and Caspian seas suffer winter dieback when grown in Iowa and Wisconsin.

Whether or not related to winter injury, the Italian alder and Iranian black alder were among the last trees to initiate growth in the spring, with trees from Bulgaria, Yugoslavia, and Estonia the earliest to flush (Table 1). Genys (6,7) found that trees from southeastern Europe (Yugoslavia, Bulgaria, Greece) flushed earliest, and those from northwestern sources (England, Norway, and Ireland) initiated growth last. In our study, the only northerly trees that flushed late were those from Scotland. Genys apparently found more of a geographic pattern of flushing than our results show.

Results presented here confirm patterns from other studies of the wide variation found in European alder. DeWald et al. (4) found the same Iranian provenances sustained major cold injury at two years of age in Pennsylvania and Canada. In a Canadian plantation, they found superior height growth in several provenances from central Europe, in particular the region from western Hungary through western Germany to northeastern France. However, on the drier Pennsylvania site, a reclaimed coal spoil area, the southern European provenances performed better. DeWald et al. (4) speculated that provenances from southern Europe have evolved to better tolerate summer droughts and therefore perform better than less drought-tolerant northern sources. Borghetti et al. (2) found differences among trees from different provenances of Italian alder in their sensitivity to drought. This variability might be used to select for high drought tolerance in alder.

Sources from central Europe, especially West Germany, have been shown in several studies (3,4,6,7) to yield trees with superior height growth. It appears, therefore, that the use of central European provenances offers the best opportunity of introducing fast-growing black alders to Ohio. However, the relative height rankings could change over time, as they did for Funk (5). Further data on both height and diameter growth should be collected in the future.

Hall and Nyong’o (10) reported serious infestations of the European alder leaf miner in all of their Iowa plantings, and estimated that the leaf miner could cause up to a 40% reduction in leaf dry weight. They also observed individual tree differences. The variation shown in the present study among provenances as well as among species could be capitalized on with a breeding program for leaf miner resistance. Genys (7) found significant variation among individual trees but not among provenances in susceptibility to the aphid Paraprociphilus tesselatus Fitch. Increasing insect resistance should be a major goal of an alder breeding program.

Clausen (3) had only 48 percent survival in 5- year-old seedlings grown in Illinois. The best survivors were from provenances in Holland, northern Italy, Bulgaria, and several central European countries; trees from Norway, Finland, and Poland survived poorly. Merrill et al. (13) found that only alders originating from latitudes north of 53 degrees (e.g., Finland, Norway, northeastern USSR, and Poland) were able to survive four growing seasons near Grand Rapids, Minnesota.

Genetic engineering of Alnus has been initiated (12), and that work combined with a stand selection and breeding effort could yield superior Alnus clones in the future. Hall and Nyong’o (10) have already developed plans for a seed orchard of European black alder.

The present study shows that variation among provenances is sufficient to directly (through selection of specific seed sources) or indirectly (through breeding and selection) make genetic advances in insect resistance, frost- and cold-hardiness, and growth rate of European black and Italian alders. Because of their nitrogen fixing ability, attractive form and foliage, and adaptability to wet sites, the alders deserve more widespread use and a concerted effort towards genetic improvement.