Genetic control of rhizome formation and rapid tillering rate in tall fescue

Tall fescue [Lolium arundinaceum, (Schreb.) Darbysh.] is commonly known as a bunch type cool season turfgrass that spreads primarily by erect tillers. Some genotypes in tall fescue were found to have rhizomes or rapidly spreading tillers. The rapid tillering types produce lateral tillers that allow the plants to spread faster laterally and produce higher number of tillers. Rhizome formation has been reported to improve the recuperative ability from mechanical damage, extend persistence under drought and temperature extremes, and enhance sod strength. Rapid tillering improves turf density, spreading ability, wear tolerance and compactness in tall fescue. The determination of the genetic control of growth habit in tall fescue is important to allow the breeders to improve the rhizome and tillering characteristics in tall fescue. The objectives of this dissertation were to: (i) study the effects of photoperiod and temperature on the rhizome formation and tillering rate, (ii) estimate the general and specific combining abilities of tall fescue parents for rhizome formation, rapid tillering rate and ground coverage (iii) to estimate the narrow sense heritability using progeny regression analysis for rhizome formation, rapid tillering rate and ground coverage, (iv) to calculate Pearson correlation coefficient between rhizome formation, rapid tillering and ground coverage, and between NDVI and rapid tillering in tall fescue, (v) Comparison between commercial cultivars and experimental breeding populations of tall fescue for rhizome formation, rapid tillering and ground coverage. The effects of environmental conditions were estimated on the growth habits of tall fescue in growth chambers with different photoperiods and day/night temperature combinations. The response of rhizome and tiller development to temperature and photoperiod varied with genotypes; longer photoperiod appeared to promote rhizome formation, regardless of temperature while lower temperature stimulated rapid tiller production in tall fescue. A diallel and polycross mating design were employed to estimate the role of additive and non-additive gene effects on the rhizome formation, rapid tillering and ground coverage in tall fescue. The field experiment was conducted at Rutgers Plant Science and Extension Research Station, Adelphia, NJ. Data were analyzed for number of rhizomes per plant, rapid tillering (number of tillers per 7.62 cm plug) and ground coverage (average of length and breadth (cm)) for analysis of variance, narrow sense heritability, general combining ability and specific combining ability, and correlation coefficient. The progenies from the rhizome parents were highest for rhizome formation whereas progenies from rapid tillering types x bunch type parents showed significant rapid tillering rate and ground coverage. Narrow sense heritability estimates for rhizome formation were low, moderately high for rapid tillering and very high for ground coverage. The combining ability analysis showed that rhizome formation was influenced by both additive and non-additive gene effects whereas tillering rate and ground coverage were controlled mainly by additive gene effects. Significant negative correlation was found between rapid tillering and rhizome formation whereas a positive correlation was found between rapid tillering and ground coverage. No correlation was found between rhizome formation and ground coverage. High correlation was found between rapid tillering and NDVI indicating that remote sensing techniques can accurately estimate tiller density in tall fescue. Another study comparing tall fescue commercial cultivars, new Rutgers’s populations and introduced Moroccan accessions for rhizome formation, rapid tillering and ground coverage was also conducted at the Rutgers Plant Science and Extension Research Station, Adelphia, NJ. The results showed significant genotypic variations between entries. Moroccan accessions had higher mean values for rhizome formation followed by Rutgers’s populations: PSG 8Az Rh, and cultivars: Ky-31, Grande, and Jaguar 3. The rapid tillering and ground coverage were greatest in the Rutgers’s populations: CCRI, LSD Comp, Regenerate and TPC; and cultivars: Turbo TF, Falcon V, and Shenandoah III. A significantly negative correlation coefficient was obtained between rhizome formation and rapid tillering over all the entries indicating with increase in rhizome formation, the rapid tillering rate decreased or vice-versa. Similarly, a significant negative correlation coefficient was found between rhizome formation and ground coverage over all the entries. However, a significant positive correlation coefficient was found between rapid tillering and ground coverage indicating that with an increase in rapid tillering, ground coverage increased in tall fescue. The results showed genotypic and phenotypic differences in tall fescue growth habit and illustrated considerable need to improve tall fescue to enhance rhizome formation and rapid tillering rate in tall fescue. Based on the presence of the additive genetic variance in the population, phenotypic recurrent selection should improve the rapid tillering and rhizome formation in tall fescue. The genetic variations present in tall fescue for the different growth habits would aid in development of superior tall fescue cultivars and its utility in different regions.Ph. D.Includes bibliographical referencesby Priti Saxen