Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/1998
Publication Date: N/A
Citation: Interpretive Summary: In warm-season grasses, roots must develop and grow from a structure called the crown node before the plant may be considered established (able to survive and develop into a mature plant). Generally the crown node is close to the soil surface. If it is above the soil surface, roots seldom develop, and the grass seedling eventually dies. Plant breeding methods were used to develop experimental populations of switchgrass (a warm-season grass) which have elevated (EC) or low (LC) crown node placement when grown in the laboratory in dim light. In the current study, the EC and LC materials and normal switchgrass were planted in the field at two Texas locations, and establishment of each of the different switchgrass types was measured. Also, relative location of the crown node was determined. In the LC material, crown nodes were placed lowest (generally at or below the soil surface), followed by the normal switchgrass, with those of EC having nodes highest above the soil surface. Both LC and EC established better than normal switchgrass. One reason for this better establishment could be that only vigorous seedlings were selected in the plant breeding process used to develop LC and EC, thus giving rise to more vigorous seedlings in these two populations compared to the normal switchgrass. Further studies will be required to more fully determine reasons for better establishment of EC and LC.
Technical Abstract: Excessive crown node elevation of warm-season grass seedlings is a major limitation to successful establishment. Crown node placement at or above the soil surface limits the opportunity for adventitious root development at the crown node. Switchgrass (Panicum virgatum L.) germplasm selected for low-(LC) and elevated-(EC) crown node placement (at 1.5 umol m-2s-1 photosynthetic photon flux density), has been developed from 'Alamo' switchgrass. The objective of this study was to determine if differences in crown node placement and other seedling morphological traits exist among Alamo (nonselected, parental), LC, and EC germplasm and if these differences affect seedling establishment in the field. Seeds were planted during April and May at Beeville, Stephenville, and College Station, TX. Each location was established with six blocks each consisting of a 2-m row of Alamo, LC, or EC seed. Seeds were planted at a 1-cm depth. Three to 10 seedlings were marked at soil level, then dug for detailed seedling measurements. There were no genotype by location interactions for any trait measured. Emergence was more rapid at Beeville for all entries because of pre-watering and better soil conditions. Averaged for the three locations, final emergence was 47, 37, and 30% for LC, EC, and Alamo. Mesocotyl length of LC germplasm averaged 5.9 mm compared to 8.4 and 9.1 mm for Alamo and EC germplasm, respectively. Even though LC seedlings had shorter mesocotyles and consequently lower crown node placement than EC or Alamo seedlings, these traits may not be directly responsible for greater establishment success.