Effect of phosphorus fertilization on arbuscular mycorrhizal fungi

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Effect of phosphorus fertilization on arbuscular mycorrhizal fungi is a well-researched topic, it is to be used as a guide or framework for your Academic Research.

Abstract

Tropical soils are highly leached, abundantly clayey and strongly acid, resulting in low mineral availability and especially phosphorus (P). The plants of this region must establish symbiotic relationships enabling them to strengthen their hydromineral nutrition. The aim of this work was to study the effect of P fertilizer application on the diversity of arbuscular mycorhizal fungi (AMF) under the rhizosphere of three Bambara groundnut (Vigna subterranea) landraces. To attain it, plants were grown in farm under different simple superphosphate (SSP) levels (0, 50, 100, 150 and 200 kg.ha-1 P2O5) in 2015 at Mendong and Soa districts. Experimental units were arranged in a randomized complete
block design with three replications. Soil and root samples were taken from the rhizosphere of three randomly selected seeds holes per experimental unit at flowering (31 days after sowing) and fruition
stages. At harvest, the roots were stored in 50% ethyl alcohol. They were stained with methyl blue and observed under an optical microscope. The soil samples allowed the trapping to be carried out in a greenhouse with sorghum as test plants. Results show that Bambara groundnut landraces were the host of several AMF species and were highly colonized with all showing hyphae, vesicles and even spores. High level of SSP (200 kg.ha-1
P2O5) significantly (p<0.001) reduced the intensity of mycorrhization as well as the diversity indices compared to the control. A density of AMF spores reaching 1930 was obtained in 100 g of trapping substrate. On the basis of morphological characteristics, 16 AMF species belonging to nine genera (Glomus, Acaulospora, Gigaspora, Racocetra, Rhizophagus, Funneliformis, Septoglomus, Diversispora and Claroideoglomous) were isolated and identified. Rhizophagus intraradices and Septoglomus constrictum were the most abundant. AMF species identified in this groundnut rhizosphere can be multiplied and used as biological fertilizer to increase its yield.

INTRODUCTION

In the world in general and in Africa in particular, about
795 million people are undernourished (one in four in
sub-Saharan Africa) and suffer from insufficient energy
intake associated with protein, vitamin and mineral
deficiencies (WFP, 2016). Moreover, population
projections predict an increase in world population. This
demographic growth far exceeds that of agricultural
production. Indeed, this agricultural production must
increase by 70% for a world population of 2.3 billion
inhabitants in 2050 (FAO, 2017). The challenge of
agricultural research is to contribute to increasing crop
yields while safeguarding the environment. Bambara
groundnut (Vigna subterranea (L.) Verdc.) could play an
important role because its seeds are highly caloric, rich in
minerals, vitamins, proteins and amino acids (De
Kock, 2013; Yao et al., 2015; Tsoata et al., 2017a).
In fact, seed legumes (Bambara groundnut) have an
important socio-economic role in tropical Africa, where
they are a tradition in the culinary habits of populations
(Brink et al., 2006). Bambara groundnut is native to
northeastern Nigeria and northern Cameroon
(Begemann, 1988). Its world production was estimated at
216575 t in 2013. In Africa, its production has not varied
considerably since 1993 and is about 300 000 t/year. In
Cameroon, production increased from 5800 t in 1993 to
38075 t in 2014 (FAO, 2017), making it the third largest
producer in the world. Bambara groundnut seeds are
used as feed for humans, poultry and livestock (Brink et
al., 2006).
They contain on average of 63% carbohydrates, 19%
protein and 6.5% fat; these values are considered
sufficient to make this legume a complete food
(Bamishaiye et al., 2011) to consider for food security (De
Kock, 2013; Yao et al., 2015). Bambara groundnut has
medicinal properties well known to local populations
(Brink et al., 2006). One of the main attributes of
Bambara groundnut is its tolerance to poor soils
(Temegne et al., 2015) and drought (Berchie et al., 2012;
Tsoata et al., 2016; 2017b) as well as its ability to
produce under conditions where groundnuts fail
completely (Jideani and Diederiks, 2014). Despite this
panoply of properties, its production remains low. This
low production is reflected in rising market prices and
scarcity of seeds (IRAD, 2013). This low production is
due to diseases and pests but above all poverty of soil
(FAO, 2003), in particular phosphorus (P) deficiency.
However, very little information exists on the biological
factors that support the Bambara groundnut growth on
poor soils. P is an essential mineral for living organisms
which is after nitrogen an indispensable element to the
good functioning of the plants (Morel et al., 2006). P is
mainly extracted from phosphate (Pi) rock (natural Pi).
Worldwide reserves of commercial natural Pi are currently
estimated at 12 billion tons with an annual consumption
of 132 million tons. These reserves are barely enough for
a hundred years (Frossard et al., 2004). As a result, P
was placed on the red list of raw materials by the
European Commission in 2014 (CE, 2014).
Plant production is limited by low P availability due to
inability to take P in orthophosphate ions form, either
directly through roots or through arbuscular mycorrhizal
fungi (AMF). Among the functional groups composing the
telluric microflora, AMF play a major role in improving
water and mineral nutrition. Thus, many plant species
rely heavily on AMF for their survival, especially in the
tropics, where the majority of soils are highly leached,
clayey and highly acidic, resulting in low mineral
availability, especially in P.
Many studies have also shown that AMF improve
water and mineral nutrition of plants and in particular the
Pi plants supply (Onguene et al., 2011; Taffouo et al.,
2014). Some studies showed that phenological stages
influence mycorrhizal activity (Mbogne et al., 2015;
Johnson et al., 2016) but little is known about the
chemical P fertilizer effect on it. Some work done in
Cameroon on the mycorrhization of bambara groundnut
did not take into account the AMF biodiversity under
cultivation (Ngakou et al., 2012; Tsoata et al., 2015).
Several researchers (Ngonkeu et al., 2003; Nwaga et al.,
2003) recommend the use of indigenous (native) AMF as
biological fertilizers because of their adaptation to local
conditions. The objective of this work was to evaluate the
AMF diversity in the Bambara groundnut rhizosphere
under Pi
fertilization.

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Additional information

Type

Project Topic and Material

Category

Agronomy

No of Chapters

5

Reference

Yes

Format

PDF

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