News Feed Forums Vegetables Genetics and nutrient density, disease resistence Reply To: Genetics and nutrient density, disease resistence

  • Julia Dakin

    February 25, 2023 at 5:24 pm

    Hi John,

    I hope my referenced links show up below,

    “While it is well established that inbreeding can increase a plant’s susceptibility to herbivores by diminishing morphological and chemical defences (Campbell et al., 2013; Kariyat et al., 2012; Kalske et al., 2014),”

    I wrote about this topic within the larger topic of nutrient density, in an online course I collaborated on (one of the teachers is Dr White, whom I contacted after being so fascinated taking the course you shared, Thank you! I would actually LOVE your feedback on the nutrient density chapter I wrote, because I have some unanswered questions that maybe you could shed some light on.

    I think that inbreeding depression is a giant and unrecognized problem in our modern food system. We strive for uniformity and consistency, we don’t practice on-farm adaptation, so that all precludes diversity and it paints a scary picture in terms of needing to adapt crops to increasingly unpredictable weather patterns (plus of course pests, diseases, loss of nutrient density and growing in nutrient poor environments).

    I do agree with you that nutritional support can help completely help these plants, but it doesn’t address underlying issues of how much modern breeding has weakened them, both through breeding under the influence of pesticides and nitrogen, and weakened their ability to form beneficial relationships with microbes that would feed and protect them, if they could. Tomato study I referenced earlier, but there is tons out there on this topic, I’m sure you’ve read Return to Resistance, Darwinian Agriculture, the Dorito Effect, Small Scale grain production, and Charles Darwin wrote an interesting book related to this called The effects of cross and self fertilisation in the vegetable kingdom (plants are more susceptible to inbreeding than animals, and it starts in a single generation). And I’m sure you’ve seen it yourself in action. Oh yes and modern vs older corns (why older corn varieties cause disease supressive soil and modern ones don’t, it’s been a while but I think you said that).

    I love this topic so much, and I could talk about it all day long, but I have a deadline so I need to come back to it. Also I will go back to the questions related to this I have for you 🙂

    Here are some references from my research a couple of years ago with some quotes. Very curious what your analysis is on these studies, and how much you think this plays into how susceptible our modern crops are (hybrids descend from 2 inbred parents), among other things.

    Bullets are all direct quotes from the studies.

    Inbreeding diminishes herbivore‐induced metabolic responses in native and invasive plant populations [2019]

    • Our findings suggest that inbreeding compromises herbivory‐induced metabolic defences in S. latifolia, and simultaneously reduces the nutritional quality of plants.

    • Weird?: herbivores consumed more biomass from, but showed reduced growth on, inbred than outbred native plants.

    • In accordance with our hypothesis, inbred S. latifolia plants from both distribution ranges for the most part incurred higher infestation damage from natural enemies in the common garden than outbreds. Plants often exhibit increased susceptibility to enemies following inbreeding

    Article about inbreeding depression and reduce immune system response

    Release from natural enemies mitigates inbreeding depression in native and invasive Silene latifolia populations

    • “Inbreeding increased flower and leaf infestation damage in plants from both ranges…”

    • Inbreeding can reduce individual fitness in the offspring generation. This inbreeding depression arises from the enhanced phenotypic expression of deleterious recessive mutations (dominance) and the reduced expression of heterozygote advantage (overdominance) following increases in homozygosity (Charlesworth & Willis, 2009)

    • As compared to outbred plants, inbreds may exhibit a lower expression of genes involved in the induction of defense compounds (Kariyat, Mena‐Alí et al., 2012; Portman, Kariyat, Johnston, Stephenson, & Marden, 2015), release reduced amounts of phytohormones essential for defense signaling (Campbell, Halitschke, Thaler, & Kessler, 2014), produce lower amounts of metabolites mediating direct or indirect defense (Campbell, Thaler, & Kessler, 2013; Kariyat, Mauck et al., 2013; Kariyat, Mauck, Moraes, Stephenson, & Mescher, 2012), or exhibit reduced structural defenses (Kariyat, Balogh et al., 2013). This can increase feeding damage on inbred plants, which in turn magnifies inbreeding depression in the presence of herbivores (Campbell et al., 2013; Carr & Eubanks, 2002) and causes negative feedback on plant population growth (Steets, Knight, & Ashman, 2007). The interactive effects of inbreeding and herbivory on fitness thus contribute substantially to the micro‐ and macroevolution of plant reproductive systems and defense strategies (Carr & Eubanks, 2014; Johnson, Campbell, & Barrett, 2015).