title: Analyses between Reproductive Behavior, Genetic Diversity andPythiumResponsiveness inZingiberspp. Reveal an Adaptive Significance for Hemiclonality.
abstract: Mode of reproduction is generally considered to have long-range evolutionary implications on population survival. Because sexual reproduction produces genetically diverse genotypes, this mode of reproduction is predicted to positively influence the success potential of offspring in evolutionary arms race with parasites (Red queen) whereas, without segregation and recombination, the obligate asexual multiplication may push a species into extinction due to the steady accumulation of deleterious mutations (Muller's ratchet). However, the extent of linearity between reproductive strategies, genetic diversity and population fitness, and the contributions of different breeding strategies to population fitness are yet to be understood clearly. GenusZingiberbelonging to the pan-tropic family Zingiberaceae represents a good system to study contributions of different breeding behavior on genetic diversity and population fitness, as this genus comprises species with contrasting breeding systems. In this study, we analyzed breeding behavior, amplified fragment length polymorphism diversity and response to the soft-rot pathogenPythium aphanidermatumin 18 natural populations of three wildZingiberspp.:Z. neesanum, Z. nimmonii, andZ. zerumbet, together with the obligately asexual cultivated congener, ginger (Z. officinale). Ginger showed an exceptionally narrow genetic base, and adding to this, all the tested cultivars were uniformly susceptible to soft-rot. Concordant with the postulates of Muller's ratchet, the background selection may be continuously pushing ginger into the ancestral state, rendering it inefficient in host-pathogen coevolution.Z. neesanumandZ. nimmoniipopulations were sexual and genetically diverse; however, contrary to Red Queen expectations, the populations were highly susceptible to soft-rot.Z. zerumbetshowed a hemiclonal breeding behavior. The populations inhabiting forest understory were large and continuous, sexual and genetically diverse, but were susceptible, whereas populations inhabiting the revenue land were fragmented and monoclonal, but were resistant. It may be possible that, when genetic recombination becomes at a premium due to the genetic constraints imparted by habitat fragmentation or pathogen pressure, Z. zerumbet.
authors.affiliation: Department of Botany, St. Thomas' College, Thrissur India.
authors.forename: Geethu E
authors.initials: GE
authors.lastname: Thomas
authors.affiliation: Plant Disease Biology and Biotechnology, Rajiv Gandhi Centre for Biotechnology Thiruvananthapuram, India.
authors.forename: Kiran A
authors.initials: KA
authors.lastname: Geetha
authors.affiliation: Plant Disease Biology and Biotechnology, Rajiv Gandhi Centre for Biotechnology Thiruvananthapuram, India.
authors.forename: Lesly
authors.initials: L
authors.lastname: Augustine
authors.affiliation: Department of Botany, University of Calicut Malappuram, India.
authors.forename: Sabu
authors.initials: S
authors.lastname: Mamiyil
authors.affiliation: Plant Disease Biology and Biotechnology, Rajiv Gandhi Centre for Biotechnology Thiruvananthapuram, India.
authors.forename: George
authors.initials: G
authors.lastname: Thomas
keywords: Muller’s ratchet; Red Queen; Zingiber spp.; breeding strategy; disease resistance; genetic diversity