Exploiting the Available Potential in Peanut Wild Species to Deal with Cercosporioses

The Senegalese peanut sector is one of the most profitable agricultural sectors in the country. Peanut is the most important crop in terms of production and harvested areas. It is mainly cultivated under rainfall conditions by farmers in the central part of the country called the peanut basin. Peanut is a cash crop providing incomes and improving livelihoods of farmers. It represents a strategic crop and its cultivation contributes to the sustainability of the integrated crop-livestock production system, the most predominant one in the semi-arid areas.

Although Senegal is among the top five producing countries in Africa, yield has declined over the years. In 2016, the harvested area was 878 659 ha with a total production of 669 329 representing over 50% of the total production of all crops mixed (FAOSTAT, 2017). Nevertheless, the increase of the production has predominantly been caused by an increase of the cultivated area rather than an increase of yield. For instance, peanut’ acreage increased by 9% in 2013/14, but the yield was lower than the previous season (922 kg/ha versus 943 kg/ha) (FAOSTAT, 2017). The national average yield is approximately 900 kg/ha on farmers’ fields (ANSD, 2017), which is below the crop yield potential estimated at 5.4 t/ha (Nigam, 2005).

This situation is partly due to some biotic constraints. The more important ones are the foliar diseases caused by fungi : early leaf spot and late leaf spot. These two diseases can caused yield lost up to 60% in semi-arid zones. In Senegal, early leaf spot is more severe than late leaf spot. It causes severe defoliation if the crop is not protected. Application of fungicides is the most common management for controlling losses. However, these products are beyond the reach of farmers and more over there are tremendous concerns in the use of fungicides because they are potentially hazardous to human health and to the environment. Therefore, the most sustainable method that involves less risk is the exploitation of host plant resistance.

Cultivated peanut has a narrow genetic basis. However, wilds species related to the cultivated species are very rich in alleles and can be used to broaden the genetic base and improve the cultivated species. Their exploitation these last decades becomes more efficient and easy with the advent of “genetics and genomics” resources.

After my diploma, I have started a work whose final objective is to create new varieties that are high yielding with greater resistance to foliar diseases. The approach involves the crossing and the development of genetic material coupled with the early selection of interesting lines using marker-assisted selection (MAS). The idea is to control with the help of molecular markers the introgression of wild fragments carrying genes of resistance to the disease and to select interesting individuals showing high level of resistance. At the end of the process, the selected lines will be highly evaluated for release or use as a breeding lines in other projects.

I did the first crosses and the F3 seeds are available. During the process, from the initial cross to the end, MAS is applied to ensure the selection of the individuals carrying the resistance genes.

The excited things about this strategy is the speed up of the breeding process. Time and resources saving because phenotyping are delay until late generations. The use of a male donor parent developed from an interspecific cross allows diversifying the narrow primary gene pool. At the same time, it allows to explore and to exploit the wild species that represent reservoir of useful alleles that can be used in breeding programs.

Aissatou Sambou, Senegal

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