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Valtcho D. Zheljazkov, Andrew M. Jones, Bharathi Avula, Victor Maddox, and Dennis E. Rowe

Podophyllotoxin is an anticancer compound found in high concentrations in Indian mayapple [ Podophyllum emodii Wall. (syn. P. hexandrum Royle.)], American mayapple ( Podophyllum peltatum L.), Eastern red cedar ( Juniperus virginiana L.), and

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Kent Cushman, Muhammad Maqbool, Ebru Bedir, Hemant Lata, Ikhlas Khan, and Rita Moraes

Podophyllotoxin is a pharmaceutical compound extracted from rhizomes of Indian mayapple (Podophyllumemodi). Leaves of American mayapple (P. peltatum) also contain podophyllotoxin, and the species is being investigated as a domestic, renewable, and alternative source of the compound. The objective of this study was to explore strategies of leaf removal that would not adversely affect regrowth of American mayapple shoots in subsequent years. Plots were established in two locations among naturally occurring populations in the wild, one in full sun and one in partial shade. Plots were 1.0 m2 and leaves were removed from plants every spring, every other spring, or every third spring. In addition, leaves were removed in early spring, soon after shoots emerged and leaves had fully expanded, or in late spring, when leaves first showed evidence of yellowing and beginning to senesce. Sexual and asexual leaves were harvested separately. Leaf number, leaf area, and dry weight were recorded. Subsamples of leaf material were extracted to determine podophyllotoxin, α-peltatin, and β-peltatin contents. Results clearly showed that leaf removal every year, in combination with early harvest, was too severe and plants lost vigor over the 4-year period of this study. Plants subjected to this treatment combination produced significantly less leaf area and dry weight than any of the other treatment combinations. Results were similar for both sun and shade locations. Lignan content was not affected by treatment. Our results indicate that leaves can be removed from mayapple plants as often as every year provided harvests are not scheduled too soon after shoot emergence.

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Kent E. Cushman, Muhammad Maqbool, Hemant Lata, Ebru Bedir, Ikhlas A. Khan, and Rita M. Moraes

Four levels of shade (0%, 30%, 55%, and 80%) were used to determine their effect on growth and lignan content of american mayapple (Podophyllum peltatum L.). Mayapple rhizomes were harvested from the wild and transplanted into plant beds on 20 Dec. 2001 using a randomized complete block design with four blocks. Growth and lignan content were recorded during spring of 2002 and 2003. Leaf samples were analyzed for the following lignans: podophyllotoxin, alpha-peltatin, and beta-peltatin. Increasing levels of shade increased shoot longevity, leaf area per plant (cm2/plant), and shoot height. Shade did not affect shoot emergence, total leaf area (cm2·m-2), or leaf dry mass (g·m-2 or g/plant). Regardless of year, podophyllotoxin and total lignan contents at 0% shade were significantly greater than those at 80% shade, and the overall trend was for decreasing contents with increasing shade. Shade did not affect alpha-peltatin content. Content of beta-peltatin was greatest at 0% shade compared to the other three shade treatments. Year affected alpha-peltatin and beta-peltatin contents, with less content of each in 2003 than in 2002. There were large numerical decreases in podophyllotoxin yield (podophyllotoxin content per unit area, mg·m-2) as shade increased from 0% to 80%, but these differences were only marginally significant (P = 0.0897). In contrast, podophyllotoxin yield was significantly greater in 2003 than in 2002 as total leaf area and dry mass significantly increased. Increasing levels of shade slightly decreased air and soil temperatures. Our results indicate that american mayapple is not a shade-requiring species. Under full sun (0% shade) shoots did not persist as long as under shade and leaves were smaller and thicker, but total lignan content was significantly greater than under shade. It appears that growers of specialty crops serving the pharmaceutical industry can establish and cultivate american mayapple under full sun, thus providing leaf biomass with high podophyllotoxin content while avoiding the cost of expensive shade structures.

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Kent Cushman and Muhammad Maqbool

American mayapple (Podophyllum peltatum) is being investigated as a domestic, renewable, and alternative source of podophyllotoxin, a precursor compound used in the manufacture of several drugs. Indian mayapple (P. emodi) is the current source of the compound. The objective of this study was to examine growth of transplanted rhizome segments of American mayapple at four transplant times during the year. Two-node rhizome segments were carefully dug with roots intact from naturally occurring wild populations near Holly Springs, Miss. Segments were dug in Oct. 2002, Dec. 2002, Feb. 2003, or June 2003. Within 1 day of each harvest, segments were transplanted into 1-gal pots containing a mixture of sandy soil and a finely ground pine bark mulch. Pots were then set in a raised bed, such that the soil surface within the pots was even with that of the plant bed. Pots and plant bed then received a 3-inch layer of pine bark mulch. Rhizome segments were harvested from pots four times during the year following the date of transplant. Rhizome and roots were separated according to new or old growth and then dried. Rhizome segments transplanted during October and December increased about 36% in dry mass during the 1-year period after transplant. This was significantly greater than an increase of 12% for segments transplanted during June. Segments transplanted during February performed intermediately, increasing by 22%. Our results show that rhizome segments of American mayapple performed better when transplanted during fall and winter compared to those transplanted during summer. Segments transplanted during spring performed intermediately.

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Kent E. Cushman, Muhammad Maqbool, and Patrick D. Gerard

American mayapple (Podophyllum peltatum L.) is a rhizomatous herbaceous perennial found in wooded areas of eastern North America and is a source of the pharmaceutical compound podophyllotoxin. To explore the possible domestication of this species, this research examined strategies for establishing mayapple in field plantings using organic mulches. Mayapple rhizome segments were harvested from the wild and transplanted to raised beds in northern Mississippi in Fall 2001. Two types of mulch (pine bark or wheat straw), two depths of mulch (7.5 or 15 cm), and two planting depths (0 or 5 cm) of rhizome segments were examined in a factorial arrangement and randomized complete block design. Data were recorded during spring of 2002 and 2003. Shoot number was not affected by mulch depth, but there was a significant interaction between mulch type and rhizome planting depth. Rhizome segments planted 0 cm deep and covered with straw mulch produced about 30% fewer shoots compared to any of the other treatment combinations. Number of emerging shoots was also affected by year, with a 33% increase in shoots from 2002 to 2003. Total leaf area and total leaf dry weight were not affected by mulch depth, but there was a significant three-way interaction between mulch type, rhizome planting depth, and year. During 2002, treatment combinations were not different, but during 2003 rhizome segments planted 0 cm deep and covered with straw mulch produced less leaf area and leaf dry weight than any of the other treatment combinations. The ratio of sexual shoots to total shoots was affected by year, with a higher ratio of sexual shoots occurring in 2002 than 2003. Grasses established in bark mulch to a greater extent than in straw mulch in 2002, but weed control was excellent for all treatments in 2003. These results indicate that rhizome segments planted 0 cm deep and covered with straw mulch consistently produced fewer shoots with less leaf area and dry mass compared to any other treatment combination. We preferred bark mulch, but we can recommend either bark or straw mulch for the purpose of establishing field plantings of american mayapple in full sun as long as rhizome planting depth is 5 cm. There was no difference between the two mulching depths used in this study; therefore, a mulch depth of 7.5 cm can be recommended because of its lower cost.

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Kent Cushman* and Muhammad Maqbool

The American mayapple (Podophyllum peltatum L.) is native to eastern North America and its leaves contain the pharmaceutical compound podophyllotoxin. Podophyllotoxin is used in the manufacture of several types of drugs used in the treatment of cancer, arthritis, and various skin conditions. With leaves being a renewable resource, the plant is a candidate for cultivation by growers of specialty crops. We are investigating strategies of establishing mayapple in field plantings. Rhizome segments were harvested from the wild and immediately transplanted to raised beds in northern Mississippi. There were three planting times, Fall 2000, Spring 2001, or Summer 2001, and three propagule types: (1) two-node rhizome segments with a terminal node and its adjacent one-year-old node, referred to as Nt+N1, (2) one-node segments with a single node, other than Nt, of unknown age, referred to as Nx, or (3) one-node segments with a single terminal node, referred to as Nt. Each spring, shoots emerged from the ground in March, grew during April, and senesced throughout May. Shoot emergence, leaf area, leaf dry mass, and shoot height were recorded each spring. Plant growth and performance can be ranked as follows. EXCELLENT: Spring-planted Nt+N1. GOOD: Fall- and summer-planted Nt+N1; fall-, spring-, and summer-planted Nx; and spring-planted Nt. FAIR: Fall-planted Nt. POOR: Summer-planted Nt. We can now recommend all three planting dates, but in the following order of preference: spring > fall > summer. We can also recommend two of the three propagule types, also in the following order of preference: Nt+N1 > Nx. The Nt propagules performed adequately when planted during fall or spring, but they did not perform well when planted during summer.

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Kent E. Cushman, Rita M. Moraes, Patrick D. Gerard, Ebru Bedir, Bladimiro Silva, and Ikhlas A. Khan

Leaves of American mayapple (Podophyllum peltatum) are being investigated as an alternative and renewable source of podophyllotoxin, a pharmaceutical compound used in the manufacture of several drugs. This study examined long-term performance of mayapple populations subjected to different harvest strategies. A naturally occurring population in shade was subjected to leaf removal treatments of frequency (every year, every 2nd or 3rd year) or timing (early or late season). Plots were 1.0 m2, established during Spring 2001, and treatments were applied from 2001 to 2004. Control plots not previously harvested were also included each year. Plants did not tolerate the severest of leaf removal treatments: early harvest time in combination with annual harvest frequency. Early annual harvests reduced total leaf dry mass and total leaf area in a quadratic manner. Late harvest conducted annually, and early harvest conducted every other year, also reduced leaf dry mass and area but not as much as early annual harvest. Plants harvested every year, early, or early every year produced fewer sexual shoots than other treatment combinations. Contents of α-peltatin, β-peltatin, and total lignans were higher for leaves harvested early than those harvested late during each year of the study, demonstrating that lignan contents were affected by leaf age and not treatment. In conclusion, our results for plants grown in shade show that leaves can be removed late in the growing season every 2nd or 3rd year or early every 3rd year without reducing long-term performance of the population. This is more restrictive than that reported for populations in full sun where plants tolerated late harvests every year.

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Muhammad Maqbool, Kent E. Cushman, Rita M. Moraes, and Patrick D. Gerard

American mayapple (Podophyllum peltatum L.) is a rhizomatous, herbaceous perennial found in wooded areas of eastern North America and is a source of the pharmaceutical compound podophyllotoxin. This research was conducted to determine the optimum duration of low temperature exposure in overcoming dormancy of fall-harvested rhizome segments for subsequent use as propagules in greenhouse plantings. Two types of rhizome segments were harvested from the wild and used in this study: two-node rhizome segments consisting of a terminal node and its adjacent one-year-old node and one-node rhizome segments consisting of a single node, other than a terminal node, of unknown age or rhizome position. For growth cycle I, rhizome segments were exposed to low temperature (≈4 °C) for 30, 45, 60, 75, or 90 days, planted in pots, and grown in a greenhouse set at 21 °C. Shoot emergence, shoots per pot, and plant height were recorded. Leaves were removed from plants when senescence first became evident, and leaf area was recorded. For growth cycle II, rhizome segments remained undisturbed in the original pots and were exposed to low temperatures (≈4 °C) for 90 days. Pots were again placed in the greenhouse and shoot emergence, shoots per pot, plant height, and leaf area were recorded. Increasing duration of low temperature exposure of rhizome segments up to 75 days appeared to increase percent emergence and plant height and decrease days to emergence, though changes in greenhouse conditions over the study period may have also influenced shoot emergence and plant growth. Two-node rhizome segments exhibited higher percent shoot emergence, shoot longevity, leaf area, and plant height than single-node segments during each growth cycle. Two-node rhizome segments also exhibited fewer days to emergence during growth cycle I. Rhizome segments produced no more than a single shoot in growth cycle I, whereas more than one shoot was produced in growth cycle II. Most of the effects of low temperature exposure during growth cycle I persisted throughout growth cycle II. These results indicate that dormancy of mayapple rhizomes can be overcome with low temperature exposure and shoots can be induced to grow at any time of year.

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Kent E. Cushman and Muhammad Maqbool

Leaves of american mayapple (Podophyllum peltatum L.) contain podophyllotoxin, a compound of interest to the pharmaceutical industry. Cultural practices for establishment of mayapple in field plantings for commercial harvest have not been investigated. A factorial arrangement of three planting dates (Fall 2000, Spring 2001, or Summer 2001) and three propagule types (Nt+N1, Nt, or Nx; as described by Maqbool et al., 2004) were used to investigate strategies for establishing mayapple plantings. Rhizome segments were harvested from the wild and transplanted into plant beds in full sun in northern Mississippi. Plant emergence was recorded during March and April of each year from 2001 to 2004. Leaves within each plot were harvested as soon as they began to yellow, from the third week of April to the first week of June each year. Propagule type and planting time interacted to affect subsequent plant growth when measured on an area basis (per square meter of growing area). In 2004, spring-planted Nt+N1 produced more shoots with greater total leaf area and dry mass than spring-planted Nx or Nt. In contrast, Nt+N1 transplanted during fall or summer was equal in performance to that of Nx or Nt. Performance of summer-planted Nt was poor, producing far less leaf area and dry mass than any of the other treatment combinations. On a per plant basis, fall-planted propagules produced greater leaf area and dry mass in 2004 than spring- or summer-planted propagules, and Nt+N1 produced greater leaf area than Nx or Nt. The effect of year was not analyzed in this study due to complications of the experimental design. In conclusion, overall plant growth and performance of spring-planted Nt+N1 can be recommended as excellent and that of fall-planted Nt as poor. All other treatment combinations can be recommended as good. These results will assist growers of specialty crops in establishing mayapple plantings under field conditions in full sun.

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Valtcho D. Zheljazkov, Charles L. Cantrell, Mateus Augusto Donega, Tess Astatkie, and Bonnie Heidel

other species that contain podophyllotoxin. Much research has been focused on the American mayapple ( P. peltatum L.), a native species in North America. Despite numerous studies on American mayapple in Poland, Russia ( Bogdanova and Sokolov, 1973