/* */ Rosa Rubicondior: Malevolent Designer News - Making a Nastier Crop Parasite

Tuesday, 10 August 2021

Malevolent Designer News - Making a Nastier Crop Parasite

Cowpea witchweed, Striga gesnerioides
The witchweed Striga gesnerioides and the cultivated cowpea: A geographical and historical analysis of their West African distribution points to the prevalence of agro-ecological factors and the parasite’s multilocal evolution potential

Creationist mode:

For admirers of Creationism's malevolent designer, the sheer inventiveness of their beloved malevolence must be breath-taking as science discovers more and more of the lengths it has gone to in order to increase the suffering of its creations.

Here, for example, is a parasitic plant, the cowpea witchweed, Striga gesnerioides, which seems carefully designed to maintain the poverty and malnutrition endemic to parts of Africa, as though malaria, sleeping sickness and other exotic diseases, and regular droughts weren't enough. The lengths it has gone to in this endeavour is revealed by a paper from scientists working for the Université de Montpellier, France, the Université Dan Dicko Dankoulodo de Maradi, Maradi, Niger and the Université Paris Diderot, France.

The importance of the cowpea as a crop is explained in the introduction to that open access paper:

Cowpea [Vigna unguiculata (L.) Walp.] is one of the most widely grown legume crops throughout the tropics and subtropics of Africa, East and Southeast Asia, Latin America, parts of southern Europe, as well as in the southern United States and in Oceania, with a 2017 world production above 7.4 million tons [1]. Its production is by far most important in Africa (7.1 Mt), particularly in West Africa, with Nigeria (3.4 Mt) and Niger (1.96 Mt) as the main producing countries. It has more than tripled since the mid-1980s in Cameroon, Nigeria, Niger, Burkina Faso, Mali, and Senegal, mostly based on an extension of cultivated areas [2]. Cowpea has a greater ability to withstand the frequent droughts of the Sahelian and Sudanian zones than any other major crop [3]. Consumed for its grains, green pods or leaves, it provides an inexpensive source of plant protein and mineral elements [4], particularly micronutrients such as iron and zinc [5] that can improve the nutritional status of resource-poor subsistence farmers [6]. Furthermore, cowpea contribution to soil fertility, through soil covering and the fixation of atmospheric nitrogen, is particularly important in smallholder farming systems where limited or no fertilizers are used [7]. However, in West and Central Africa, cowpea faces severe abiotic and biotic constraints. Abiotic stresses mostly include severe drought [8, 9] and salinity [10, 11]. Biotic pests include bacterial, fungal and viral diseases [12], insects [13], nematodes [14], herbivores [15], and particularly the parasitic weed Striga gesnerioides (Willd.) Vatke (Scrophulariaceae), an obligate root-parasitic flowering plant [16, 17]...
Brilliant, eh? Just when the people of West Africa had discovered and cultivated a crop which can withstand the frequent droughts and which provides "an inexpensive source of plant protein and mineral elements" and so "can improve the nutritional status of resource-poor subsistence farmers", and which improves soil fertility by fixing nitrogen, up pops Creationism's beloved malevolence and designs a parasitic plant which, devastates the crop and ruins the soil!

Creationist mode:

Or so Creationist advocates of the childish notion of intelligent [sic] design would have us believe.

But of course the rational, grown-up scientific explanation is much more sensible and based on observable evidence.

Witchweeds or Striga is a family of parasitic plants of the Orobanchaceae family. They are hemiparasitic, obligate parasites on the roots of plants, which are essential for their initial germination and development, after which they are capable of independent existence. There may be over forty different species.

Figure 42 Small Witchweed, Striga bilabiata bilabiata
Three species in particular, Striga asiatica, S. gesnerioides, and S. hermonthica, can devastate the crops of subsistence farmers. The crops most at risk include maize, millet, sorghum, sugarcane, rice and legumes. Because of the heavy toll on the water and nutrients, infestation can resemble the results of nutrient deficiency and drought. Entire crops can be lost.
The plants can each produce between 90,000 and 500,000 seeds which, like those of O. ramosa can lie dormant in the soil for over 10 years. As with O. ramosa, the seeds of Striga germinate in response to chemicals produced by plant roots.

The mechanism by which Striga find and attach themselves to the roots of their hosts is ingenious. Having been initially stimulated to germinate, the seed sends out a root-like structure that probes the soil, releasing an oxidizing enzyme that dissolves plant roots causing them to produce quinone. When the concentration of quinone reaches a threshold, a haustorium develops which then follows the quinone concentration gradient until it makes contact with the root. At that point the cells in the haustorium multiply rapidly to form a wedge-like structure and the cells elongate to force the haustorium into the root. Finger-like projections, called oscula then grow from the haustorium to make contact with the conductive fibres in the root and begin drawing water and nutrients into the seed, which then produces cotyledons to grow upwards to become a new plant. In Africa, witchweed affects 40% of arable land and costs some $30 billion in lost crops per annum. A little gift from the intelligent designer to a continent already suffering from drought and famine.

I devote a section to witchweeds in my popular, illustrated book, The Malevolent Designer: Why Nature's God is not Good.

It is clear too now that the success of this particularly devastating witchweed is due to its ability to evolve according to local conditions, by which means it is able to exploit the local conditions and the local crops more effectively.

As the scientist say in the abstract to their paper:

The increasing severity of Striga gesnerioides attacks on cowpea across West Africa has been related to its prolificity, seed mobility and longevity, and adaptation to aridity, in a context of agricultural intensification. To understand this fast extension, we analyzed (1) the distributions of the crop and the witchweed with ecological niche modeling and multivariate climate analysis, and (2) the chronological information available from collections and the literature. The ecoclimatic envelope of S. gesnerioides attacks on cowpea is the same as on wild hosts. Consistently, the modeled distribution of cowpea infestations is closely similar to the simple superposition of the parasite model (involving all hosts) and the crop model. Striga gesnerioides infestations are restricted to the driest component of the cultivated cowpea ecoclimatic niche, corresponding to the Sahelian and Sudano-Sahelian belts and the Dahomey gap. Thus, the parasite distribution, determined by its own requirements, does not constrain cowpea cultivation under Guinean climates. The spatial and temporal distributions of S. gesnerioides field infestations are consistent with an earlier impact on cowpea production in eastern West Africa, related itself to a similar trend in cowpea cultivation intensification from Niger, Nigeria and Benin to Burkina Faso and Ghana. Mali and Senegal were affected later, and literature reports of Senegalese strains of S. gesnerioides from the wild developing virulence on cowpea offer a model for the diffusion of witchweed parasitism by multilocal evolution, through host-driven selection, instead of epidemic diffusion. A contrario, in Côte d’Ivoire, cowpea is much less widespread, so the parasite has remained confined to the wild compartment. Thus, both historical and ecogeographic analyses refute the vision of S. gesnerioides as an invader. Instead, they point to the increasing importance and intensification of the crop, and the consequent loss of biodiversity, as the main drivers of the extension and diversification of its crop-specific strains.

A creationist would, because dogma demands it, deny that this is evidence of the evolutionary adaptability of S. gesnerioides because nothing evolves and no change in a species happens by the operation of natural forces alone, so it must be the result of conscious design by a magic entity capable of directing such changes.

What they will never say though, is why they a) equate this malevolent entity to the supposedly omnibenevolent god of the Bible and Qur'an and b) would prefer us to see this entity as a malevolent, misanthrope who hates its creation and is forever creating new ways to make it suffer, than have us accept that these things can arise by a natural process in which neither intelligence nor intent, malevolent or benevolent, play any part.

Obviously, there is a pollical agenda at work which requires people to believe these Creationist frauds, even at the expense of implied denigration of the god they purport to worship.

Thank you for sharing!

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