The relationship between morphology changes and antioxidant enzymes activity during somatic embryogenesis of long-term-maintained callus of Zoysia matrella [L.] Merr.

A callus line of manila grass (Zoysia matrella [L.] Merr.) has been maintained for 8 years in our lab. The present study investigated changes in ultrastructure and antioxidant enzyme activity during regeneration of the callus and examined the correlation between these changes and regeneration ability. The changes in fresh weight and diameter of the callus over time could be described by a sigmoidal growth curve with different stages. Electron microscopy revealed small embryonic callus cells, isodiametric in shape, with large, obvious nuclei and dense cytoplasm. The cellular structures and morphology changed dramatically as regeneration proceeded. Of particular note was the formation of folded scutellum-like embryos at 14 d, which might be the turning point for morphological differentiation. Catalase (CAT) and peroxidase (POD) activities were the lowest at 14 d, the same time when superoxide dismutase (SOD) activity was the highest. Thus, we speculate that the formation of the scutellum-like structures is associated with higher activity of SOD and lower activities of CAT and POD.

Susceptibility of Zoysiagrasses to the Fall Armyworm (Lepidoptera: Noctuidae)

Growth and developmental parameters of the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), were evaluated on 41 new zoysiagrass taxa (Zoysia spp. Willd.), which belong to an increasingly popular group of warm-season turfgrasses, in comparison with 5 commercially available zoysiagrass taxa and 1 known susceptible Paspalum L. taxon. Results from two no-choice growth chamber trials indicated that the new Zoysia japonica Steud. taxa were unfavorable for the development of fall armyworm larvae in general compared with the susceptible Paspalum taxon. This was evidenced by significantly lower larval and pupal weights and survival and longer time to pupation and adult emergence, pointing to antibiosis in these zoysiagrass taxa. The new Zoysia matrella (L.) Merr., Zoysia macrostachya Franch. & Sav., and Zoysia sinica Hance taxa seemed more favorable than Z. japonica taxa, as evidenced by numerically higher larval and pupal weights and survival and shorter duration to pupation and adult emergence. Taxa that consistently showed low larval survival were identified for further testing.

Effect of lead on growth of warm season turf grasses

The ability to tolerate metals targeted for remediation in existing soil conditions is one of the important features possessed by plants used in phytoextraction programs. Pot experiments were conducted using Stenotaphrum dimidiatum (L.) Brongn, Zoysia matrella var. pacifica Goudsw and Axonopus compressus (Sw.) P. Beauv plants to identify ability of these turf grasses to withstand and tolerate lead when grown in contaminated soil from across Musi River region of Hyderabad which had lead metal in concentrations higher than permissible limits. Plants were exposed to 131.2, 223.3 and 326.2 mg kg-1of lead in contaminated soil and examined under three metal exposure periods of 120, 240, and 360 days. Control samples were obtained by growing plants in normal soil with 42.2 mg kg-1of lead. The pot cultures were maintained at a nursery under normal day light conditions and shoots were harvested every 60 days during the 360 days of study period from June 2017 to June 2018. Results showed that for all three grasses a decrease in heights was seen with an increase in soil lead concentrations and exposure time. Decrease in lengths was more for roots than shoots.Zoysia matrella was the most lead affected plant with a mean phytotoxicity of 14.7% compared to 10.9 and 8.5% seen in Stenotaphrum dimidiatum and Axonopus compressus. Lead tolerance was highest for Axonopus compressus with Metal tolerance index (MTI) of 91.5%, followed by Stenotaphrum dimidiatum (89.1%) and least by Zoysia matrella (85.3%). At the highest given soil lead concentration of 326.2 mg kg-1with Axonopus compressus was found significantly better having higher tolerance index compared to Zoysia matrella. The study concludes that Axonopus compressus popularly known as Carpetgrass has a greater scope for use in lead phytoextraction programs compared to the other two tested grasses as it had the ability to tolerate and withstand lead in contaminated soil at higher concentration