Screening for resistance to aphid in local cultivated
cowpea varieties for a marker-assisted breeding programme in Botswana

Botswana University of Agriculture and Natural Resources (BUAN)

The BUAN/ NARDI cowpea improvement team. Left to right, back row: Ms Marang Mosupiemang, Prof Samodimo Ngwako; Dr Motlalepula Sethunya Tait (PI); Dr Lekgari Lekgari (Co-PI); Prof Bamphithi Tiroesele. Front row, left to right: Dr Tiny Motlhaodi; Mrs Galalea Gaonosi; Mr Boisy Tshegofatso; and Ms Nametso Nkane.

PROJECT OVERVIEW

Background

Cowpea is the most economic crop in African countries. However, production is impacted by its vulnerability to biotic stress such as aphids (Aphis craccivora Koch). Development of resistant cultivars is of paramount importance in cowpea production. Previous studies have identified aphid resistance in two Botswana accessions: B261-B and B383, however, the genetic basis of this resistance is unknown. This study also aims to establish whether cowpea varieties known to be resistant to aphids in other countries are also so in Botswana. This pilot projects sets to establish the foundations for a marker assisted cowpea breeding programme at BUAN.

Objectives

To phenotypically and genotypically evaluate and confirm local cowpea accessions for aphid resistance.
To introgress aphid resistance from the aphid resistant accessions into localaphid susceptible cowpea commercial varieties.
To phenotypically and genotypically evaluate the F2 segregating population for aphid resistance.
To build capacity and establish research collaborations for the cowpea crop improvement programme.

seed multiplication Chokwe Celestina_edited.jpg

Progress to date

Group has successfully sourced local plant genetic materials from Botswana National Plant Genetic Resource Centre and Western African Research Institute (KT partners).

Objective 1

14 cowpea (8 local and 6 exotic) accessions were planted in the Screenhouse which happened in February 2024. Planting was delayed because of late receipt of the exotic accession. Eventually local B383 was eliminated from the trials due its unavailability.
Plants were infested after 7 days of plant emergence. Based on the observations group was able to conclude that Tswana accession showed lower aphid population counts compared to other genotypes.
In visual plant damage observations Blackeye and ER7 were found to be highly susceptible to aphid damage while Tswana variety showed no symptoms. Data processing is still ongoing.
gDNA successfully collected from 6 plants per genotype. Amplification still pending due to delays in the delivery of reagents.
Data collection for agronomic traits is still ongoing.

Objective 2

Polymorphism test results are pending due to long heatwave periods.

Objective 4

One MSc student registered for MSc Crop Science and the funding is only for the research fees. Student will be taking part in conducting aphid screening and breeding experiments.

iii

i and ii)Team performing aphid infestation experiments on cowpea plants. iii) 27 days after infestation, number of nymphs, adult and winged adult aphids were calculated. Aphid damage on the plants was also observed and scored accordingly. iv) Project's laboratory team running PCR-based polymorphism tests to screen for aphid resistance.

PROJECT TEAM MEMBERS

Dr Motlalepula Sethunya Tait

Principal Investigator (PI), Botswana University of Agriculture and National Resources (BUAN), Botswana.

Dr Tait obtained her PhD in Plant Biotechnology from the University of Stellenbosch in 2016. Between 2016 and 2021 she worked as a Biotechnologist/Researcher for Department of Agricultural Research. Since 2021 Dr Tait has been working in Botswana University of Agriculture and Natural Resources (BUAN).