Asexual reproduction and plants that cover the reproductive bases https://food-hacks.wonderhowto.com/how-to/peel-entire-bulb-garlic-without-actually-peeling-0154867 https://www.wideopeneats.com/citrus-hybrids/ https://www.pri.org/stories/2015-05-05/earths-biggest-living-thing-might-be-tree-thousands-clones

Asexual Reproduction + = + = N n NN Nn nn + = + = Note: At this point in the figure, the antipodals and synergids are deleted and only the fertilized endosperm nuclei (now 3n) and fertilized egg (now 2n) are shown. Only the fertilized egg is carried to the Punnett square.

Asexual reproduction: The clone is immortal Example #1: Allium sativum “As far as we know, garlic in cultivation throughout history has only been propagated asexually by way of vegetative cloves, bulbs, and bulbils (or topsets), not from seed. These asexually propagated, genetically distinct selections of garlic we cultivate are more generally called "clones". Yet this asexual lifestyle of cultivated garlic forgoes the possibility of combining traits proffered by interpollinating diverse parental stocks.” http://www.ars.usda.gov/Research/docs.htm?docid=5232

Asexual reproduction: The clone is immortal But what if you want to change it? Perspectives on breeding garlic Induced mutation Transgenics Gene editing Restore sexual fertility https://www.researchgate.net/publication/40105133_Garlic_breeding_system_innovations

Asexual reproduction: The clone is immortal Example #2: Populus tremuloides Pando clone The world's heaviest living thing: 6 million kilograms 47,000 genetically identical ramets Aspen is dioecious species - this clone is one big male One of the world’s most ancient organisms (?) Threatened! https://www.pri.org/stories/2015-05-05/earths-biggest-living-thing-might-be-tree-thousands-clones https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0203619

Red Delicious x Virginia Ralls Janet Asexual reproduction: somatic mutations plus sexual reproduction option Delicious 1881 Red Delicious 1880 somatic mutation in Delicious Many subsequent mutations selected Fuji Red Delicious x Virginia Ralls Janet 1930s http://www.applename.com/

A transition to Apomixis + = n n n N N N N N N N n N n + = N N N N N N N n NN Nn nn + = N N N n n n n n n n N n N + = n n n n n n Note: At this point in the figure, the antipodals and synergids are deleted and only the fertilized endosperm nuclei (now 3n) and fertilized egg (now 2n) are shown. Only the fertilized egg is carried to the Punnett square.

Seeds without sex: Apomixis Apomixis = parthenogenesis: Development of an egg without fertilization (Parthenocarpy = development of fruits (seedless) without fertilization) Allows for seed propagation of heterozygotes: genetically identical from generation to generation. Obligate Facultative  http://ipm.ucanr.edu/PMG/WEEDS/annual_bluegrass.html

Seeds without sex: Apomixis Prevalence 400 species; 40 families; Common in Poaceae, Asteraceae, Rosaceae Examples Tripsacum Poa pratensis Pennisetum Dandelion (Taraxacum spp) Rubus https://www.gardeningknowhow.com/edible/herbs/dandelion/dandelion-seed-growing.htm

Seeds without sex: Apomixis Mechanisms No (or altered) meiosis to produce unreduced (2n) female gametophyte (embryo sac) Autonomous embryo formation without fertilization, or Endosperm development may be triggered by fertilization. (pseudogamy = fertilization of central cell but not egg)  

Seeds without sex: Apomixis Hand and Koltunow. 2014. Genetics 197: 441-450

Seeds without sex: Apomixis Genetic basis Apomixis loci and candidate genes Lots of breeding effort; little success Epigenetics? “Our results highlight the potential of heritable DNA methylation variation to contribute to population differentiation along ecological gradients.” Preite et al. 2015. https://onlinelibrary.wiley.com/doi/full/10.1111/mec.13329

Seeds without sex: Apomixis Economic implications of apomixis Hybrid seed production?  Transgenic apomict escape? Evolutionary implications of apomixis Obligate Facultative

Covering the bases: asexual reproduction + apomixes + sexual reproduction = n n n N N N N N N N n N n + = N N N N N N N n NN Nn nn + = N N N n n n n n n n N n N + = n n n n n n Note: At this point in the figure, the antipodals and synergids are deleted and only the fertilized endosperm nuclei (now 3n) and fertilized egg (now 2n) are shown. Only the fertilized egg is carried to the Punnett square.

Two plants that cover the reproduction and seed bases: Citrus and the Himalayan blackberry Center of origin: Southeast Asia Subsequent selection and diversification Genome formula and size: Most cultivated forms are 2n = 2x = 18 ~ 400 – 600 Mb Traits of economic importance: nutrition, flavor, aroma Cool facts: The genus covers the reproductive bases. Sexual forms as well as facultative and obligate apomicts. Male and female sterility are common. Parthenocarpy is a common feature. Asexual propagation is common. Selection of somatic mutants has led to much of the diversity we see and eat today.

Citrus: The family tree https://www.nationalgeographic.com/magazine/2017/02/explore-food-citrus-genetics/

Citrus – more insights: Pummelo, citron, and some mandarin ancestors: obligate sexual reproduction No apomixis High genetic diversity Orange, grapefruit, lemon satsuma, clementine: Bud sport selections Apomixis (nucellar embryony) Maternal sporophyte tissue Often polyembryonic seeds Lower genetic diversity

Citrus – more insights: Grapefruit: Spontaneous hybrid of pummelo and sweet orange. Selection for seedlessness and pigment Tangelo: Intentional cross of grapefruit x mandarin Selection for seedless-ness, pigment, and flavor Tahiti lime: Seedless triploid from 2x X 4x cross

Rubus armeniacus: The Himalayan (Armenian) blackberry Center of origin: Armenia/Iran Introduced to Europe and North America in 19th century Rubus spp. Genome formula and size: 2x – 18x; 230-1203 Mbp Traits of economic importance: Invasiveness, delicious fruit, habitat Cool facts: The perfect weed? Thanks to Luther Burbank https://owlcation.com/stem/Himalayan-Blackberry-Plants-in-BC-Invasive-But-Beautiful

Is the Himalayan blackberry the perfect weed? Attribute Description Flower Hermaphroditic Pollination biology Self and outcross Apomixis Facultative Seeds Small and numerous Vegetative propagation Yes Ploidy level 4x(?) Protection Thorns Attraction Tasty fruit Was Luther Burbank the “father” of this “perfect weed”? “Himalayan Giant” for sale in his catalog in 1894 promo.idahopotato.com https://www.npr.org/sections/thesalt/2016/08/29/491797791/the-strange-twisted-story-behind-seattles-blackberries