Effects of the shoot-cutting method on field propagation in napiergrass (Pennisetum purpureum Schum.)

Abstract

In this study, the effects of shoot-cutting method on propagation using overwintering napiergrass (Pennisetum purpureum Schum.) buds were examined under soil conditions compared with plant growth regulators (PGRs) that are used as an effective method for increasing adventitious buds of several gramineous crops. To increase adventitious budding, we cut shoots of napiergrass at 2 weeks after planting and treated with the following four types of PGR in comparison with shoot-cutting: 4.44 mM BA as cytokinin, 3.63 mM triazine as anticytokinin, 5.37 mM NAA as auxin, and 2.22 mM TIBA as antiauxin, either by injection or direct spraying onto the buds. A large number of adventitious buds were observed in BA- and TIBA-injected buds at 4 WAT compared to shoot-cut or PGR-sprayed buds. However, an extremely low survival rate for tiller-divided plants (nursery plants) derived from both BA- and TIBA-injected plants was observed compared with non-PGR controls. Similar trends on the survival rate and relative tiller number in main shoot-cut plants derived from intact buds (without PGR treatment) were also observed in a repeat trial. The present study demonstrated that the method of shoot-cutting could contribute to increasing propagation efficiency for nursery plants compared with exogenous PGR application, and would be a practical method for increased nursery propagation of napiergrass under soil conditions.