Performance of Container-grown Seedlings of American Chestnut Backcross Hybrids Bc3f3 Generation in Central Louisiana

Seedlings from two families of the BC3F3 backcross generation of the American chestnut (Castanea dentata) and Chinese chestnut (C. mollissima) were cultured in 2013 in Missouri using the Root Production Method®, a container-based system used to avoid disease problems associated with bareroot nursery production. After culling part of the seedlings at initial leaf formation in a greenhouse, both the culled and the remaining “kept” seedlings were transplanted into containers of 1.33, 1.57, and 2.62 L and grown outdoors. Seedlings, remaining in their containers, were brought to central Louisiana in mid-June 2013 and cultured outdoors. Half of the seedlings were harvested in September, and the other half continued to grow until storage in a cold room in mid-November. Of the seedlings harvested in September, family W4938 (W) seedlings had 90 percent more biomass than family D3862 (D) seedlings. Patterns of biomass allocation from each component within a seedling did not differ between families. All but one seedling had short (less than 6 cm) taproots, whereas the lengths of first-order lateral roots and adventitious roots were similar to the depths of the containers used. In family W, seedlings cultured in the 2.62 L containers were larger in size and biomass than those of the smaller volumes. Seedlings were outplanted in central Louisiana in late March, 2014. Firstyear survival was only 47 and 33 percent for the W and D seedlings, respectively. High summer temperature and local wet planting spots are suspected of causing the high seedling mortality.