Sanitary quality of seed of Paspalum species

Brazil has been developing research for selection of native species of Paspalum for use as turfgrass, nevertheless little is known about the sanitary quality and pathogens associated to the seeds, being the aims of this study. Subsamples of 100 seeds of two accessions of Paspalum notatum Flügge (PN 01 and PN 04) and one accesses of Paspalum lepton Schult. (PL 01) were submitted to the blotter test at 20 °C with a 12-h photoperiod for 7 days. The Penicillium and Curvularia genus incidence were highest in the three accessions of Paspalum. The seed health quality was variable between accessions, with more than 56% of incidence of the fungus Curvularia on the seeds. This study reported for the first time the occurrence of Curvularia spp. and Cladosporium herbarium in seeds of P. lepton, in the Northeast region of Brazil.


Introduction
The Paspalum L. genera are among the main warm season grasses used for lawns. The seed propagation contributes to the decrease of the cost of establishment, besides maintaining the exact characteristics of the mother plant genotype, because they are apomictic species (Maximino et al., 2017). Paspalum notatum has been widely used in lawns in urban areas because of its resistance to trampling, drought, heat and high rate of establishment (Trenholm et al., 2001). In Brazil, a mixture of biotypes and ecotypes of Paspalum notatum var. notatum, known as "grama-batatais", is used in gardens, functional areas of airports, industrial parks and roads, demonstrating the potential of this native species for use as tropical turfgrasses (Souza et al., 2016;Souza et al., 2020).
Regarding sanitary quality, little is known about the pathogens associated with seeds of tropical forages produced. The pathogens present in seeds can affect germination, seedling development and production of forage plants in the field. The introduction of the pathogen through the seeds is a possible source of long-distance dissemination and could play a role of transferring them to a new place (Lazarotto et al., 2012;Rioux et al., 2014). Pathogens can also prevent seeds from being traded on the global market, as some countries may have restrictions on seeds with sanitary issues (Mallmann et al., 2013;Santos et al., 2014). Seed health testing to detect seed borne pathogens is an important key step in the management of crop diseases. This study aims to evaluate the sanitary quality in Paspalum notatum and P. lepton accessions with potential for use as turfgrass.
The health analyses of the seeds were conducted at the Seed Pathology Laboratory (Institute of Agronomy of Pernambuco -IPA). Four repetitions of 100 seeds were distributed on three sheets of sterilized filter paper, moistened with sterilized distilled water and placed in plastic boxes ('Gerbox'), previously disinfected with 1% sodium hypochlorite (Brasil, 2009). The seeds were incubated for seven days under a photoperiod of 12 hours at a temperature of 20 ± 2 °C. Fungal structures were observed under a stereoscopic and optical microscope and identified with the help of an identification key (Barnett and Hunter, 1972). The results presented the percentage incidence for individual pathogen. The experimental design was completely random and the means compared with Tukey's test at the 5% probability level.

Results and Discussion
The following fungi were identified in seeds of accessions of Paspalum: Curvularia spp., Penicillium spp., Alternaria spp., Cladosporuim herbarum, Stemphyllium spp. (Figure 1), Rhizopus spp. and Bipolaris sp. The Penicillium and Curvularia genus incidence were highest in the three accessions of Paspalum. Among the accessions of P. notatum, it was observed that the PN 04 access was more susceptible than the PN 01 access, presenting a greater number of species of fungi. Some important and potentially pathogenic fungi have been detected in the seeds of Panincum maximum and Brachiaria spp., such as Curvularia, Phoma, Fusarium, Exserohilum, Cercospora, Fusarium, Cladosporium and Helminthosporium (Mallmann et al., 2013;Marcos et al., 2015;Silva at al., 2019). The species of phytopathogenic fungi most frequent in seed lots of Paspalum guenoarum ecotype "Azulão" were Bipolaris micropus, Curvularia geniculata, Fusarium incarnatum and Phoma herbarum  This study reported for the first time the occurrence of Curvularia sp. and Cladosporium herbarum in seeds of P. lepton, in the Northeast region of Brazil. The genus Curvularia had the highest incidence among fungi identify (above 56%) in the all accessions (Figure 2). In general, other studies report the susceptibility of the Paspalum species to attacks of fungi from genre Bipolaris micropus, Epicoccum sorghinum, Fusarium incarnatum, Curvularia geniculata and Curvularia lunata (Lin et al., 2015;Malkanthi et al., 2016;Gasparetto et al. 2017). The Curvularia leaf spot is one of the important diseases in golf courses maintenance management (Lin et al., 2015). Symptoms are characterized by reddish-brown or black spots. In some cases, the spots are confined to the top or bottom of the glumes and have a clearer center (Prabhu et al., 1999).

Conclusions
Additional studies are necessary to verify the potential for transmission of and survival of these phytopathogenic fungi in the Paspalum genus seeds and selection of products for the control of pathogens in this grass.