Fungal associations in gametophytes and young sporophytic roots of the fern Nephrolepis exaltata

Abstract

-Information is limited on the presence of endophytic fungal associations in green gametophytes and young sporophytes of extant ferns. Nothing is known about their presence in Polypodiales, the largest order among extant ferns. We screened chlorophyllous gametophytes and young sporophytes of Nephrolepis exaltata (L.) Schott., (Lomariopsidaceae, Polypodiales) growing naturally on soil, brick and coir for the presence of fungal endophytes. Gametophytes and young sporophytes growing on different substrates were invariably colonized by septate endophytic fungi. Hyaline or brown, regularly septate, inter-or intracellular hyphae with moniliform cells or microsclerotia characterized septate endophytic fungi. However, only the roots of young sporophytes growing on soil and bricks harboured arbuscular mycorrhizal (AM) fungi. The AM morphology conformed to the intermediate type with intracellular hyphal coils, arbusculate coils and intercellular hyphae. No AM fungal spores could be retrieved from the soil on which gametophytes and young sporophytes were growing. The observations in this study support the idea that the septate fungal endophytes could confer an ecological advantage on colonized individuals, especially on nutrient deficient substrates.

Micorriza arbuscular, Mucoromycotina y hongos septados oscuros en helechos y licófitas con distribución en México: una revisión global

“…Las especies con mayor número de muestras fueron Pteris vittata L. con 12 registros, Pteridium aquilinum (L.) Kuhn in v. d. Decken con nueve, Adiantum capillus-veneris L. con ocho, Botrychium virginianum (L.) Sw. con seis, Pteris cretica L. y Psilotum nudum (L.) , 2009, Dhillion, 1993, Fernández, Messuti, & Fontenla, 2013, Gemma et al, 1992, Hepden, 1960, Iqbal, Yousaf, & Younus, 1981, Kessler et al, 2014, Khade & Rodrigues, 2002, Kovács, Kottke, & Oberwinkler, 2003, Kovács, Balazs, & Penzes, 2007, Laferrière & Koske, 1981, Lara-Pérez et al, 2014, Lara-Pérez, 2007, Lara-Pérez, 2015, Laursen, Treu, Seppelt, & Stephenson, 1997, Lee, Eom, Lee, & Lee, 2001, Lesica & Antibus, 1990, Leung, Ye, & Wong, 2007, Liu, Zhu, Chen, Christie, & Li, 2005, Martínez, Chiocchio, Em, Rodríguez, & Godeas 2012, Mishra, Sharma, & Gatphoh, 1980, Moteetee, Duckett, & Russell, 1996, Muthukumar, Sathiyaraj, Priyadharsini, Uma, & Sathiyadash, 2014, Muthukumar & Prabha 2012, Muthukumar & Prabha 2013, Muthuraja, Muthukumar, Sathiyadash, Uma, & Priyadharsini, 2014, Nadarajah & Nawawi, 1993, Palmieri & Swatzell, 2004, Reyes-Jaramillo et al, 2008, Santhoshkumar & Nagarajan 2014, Schmid & Oberwinkler, 1996, Schmid, Oberwinkler, & Gómez, 1995, Schmid & Oberwinkler, 1993…”

“…Estudios recientes, confirman la presencia de micorriza arbuscular en gametofitos cordados de helechos, que crecen al interior de un bosque subtropical perennifolio en Japón (Ogura-Tsujita et al, 2015). Por el contrario, gametofitos de las especies Pteris vittata y Nephrolepis exaltata, consideradas como especies pioneras, demuestran que no son susceptibles a la colonización por HMA, formando micorriza únicamente en el esporofito diploide (Lloyd, 1974;Bonfante & Selosse, 2010;Wang et al, 2012;Muthukumar & Prabha 2012). Las herramientas moleculares pueden ayudarnos en la identificación taxonó-mica de las especies de hongos que colonizan tanto a gametofitos como a helechos y licófitas (Pryer et al, 2004;Ogura-Tsujita et al, 2015).…”

Pteridophyte fungal associations: Current knowledge and future perspectives

“…In addition to Glomeraceae, they also found members of the Claroideoglomeraceae, Gigasporaceae, Acaulosporaceae, and Archaeosporales fungi previously unknown in ferns but which are widespread in thalloid liverworts and hornworts (Bidartondo et al, 2011;Desir o et al, 2013;Field et al, 2015b). There is now a pressing need to extend these molecular studies to Polypodiales since recent light microscope studies indicate the presence of similar associations in a range of genera; Adiantum, Pellaea (Turnau et al, 2005), Dryopteris (Reyes-Jaramillo et al, 2008), Nephrolepis (Muthukumar & Prabia, 2012) and Pteris (Martinez et al, 2012), and particularly since the discovery of both Glomeromycota (Glomeraceae and Diversisporaceae) and Mucororomycotina in Anogramma leptophylla from the only fungal DNA sequencing study to date on the sporophytes of a member of the Polypodiales (Figs. 2c, 2d) .…”

“…Apart from a handful of electron microscope studies and even fewer molecular investigations, our knowledge of the occurrence of mycorrhizas across pteridophytes is based solely on light microscope observations. The reviews by Rayner () and Burgeff () and more recently by Wang & Qiu () and Lehnert et al () together with the exhaustive survey of 420 taxa by Boullard (), check lists for the British flora (Harley & Harley, ; Newman & Reddell, ), and field surveys in countries across the world—for example: China (Zhao, ; Zhang et al, ), Costa Rica (Lesica & Antibus, ), Ecuador (Lehnert et al, ; Kessler et al, ), Honduras (Zubek et al, ), India (Muthukumar & Udaiyan, ; Sudha & Ammani, ; Muthukumar & Prabia, , ; Muthuraja et al, ), Lesotho (Moteetee et al, ), Mexico (Lara‐Pérez et al, ), New Zealand (Cooper, ), Pakistan (Iqbal et al, ), Malaysia and Indonesia (Nadarajah & Nawawi, ; Kessler et al, ), Reunion (Kessler et al, ), USA (Laferrière & Koske, ; Berch & Kendrick, ; Gemma et al, ; Gemma & Koske, ), all report a high incidence of mycorrhizas but perhaps lower than for seed plants. These listings have serious failings.…”

“…Whether or not dark septate hyphae (see Burgeff, ; Boullard, ; Iqbal et al, ; Dhillon, ; Nadarajah & Nawawi, ; Moteetee et al, ; Mandyam & Jumpponen, ; Fernández et al, ; Lehnert et al, ; Sudová et al, ; Muthukumar & Prabia, ; Muthuraja et al, ; Lara‐Pérez et al, , for examples) form any kind of mutualistic relationship with pteridophytes has not been explored, but on the evidence to date this would seem unlikely. We are not aware of any published ultrastructural study showing such hyphae in a host cell with healthy cytoplasm in any land plant let alone a pteridophyte, and definitive evidence for a function in seed plants has not yet been forthcoming (Jumpponen & Trappe, ; Jumpponen, ; Newsham, ).…”