Selection of full-sib families of Panicum maximum Jacq under low light conditions

Abstract

The silvopastoral system is a viable technological alternative to extensive cattle grazing, however, for it to be
successful, forage grass genotypes adapted to reduced light need to be identified. The objective of this study was to
select progenies of Panicum maximum tolerant to low light conditions for use in breeding programs and to study
the genetic control and performance of some traits associated with shade tolerance. Six full-sib progenies were
evaluated in full sun, 50% and 70% of light reduction in pots and subjected to cuttings. Progeny genotypic values
(GV) increased with light reduction in relation to plant height (H) and specific leaf area (SLA). The traits total dry
mass accumulation (DM) and leaf dry mass accumulation (LDM) had GV higher in 50% shade and intermediate in
70% shade. The GV of tiller number (TIL) and root dry mass accumulation (RDM) decreased with light reduction.
The highest positive correlations were obtained for the traits H and RDM with SLA and DM; the highest negative
correlations were between TIL and SLA and RDM, and H and LDM. The progenies showed higher tolerance to 50%
light reduction and, among them, two stood out and will be used in breeding programs. It was also found that it is not
necessary to evaluate some traits under all light conditions. All traits had high broad sense heritability and high
genotypic correlation between progenies in all light intensities. There is genetic difference among the progenies
regarding the response to different light intensities, which will allow selection for shade tolerance.