Limitations of the study

Although this research has brought into light some significant results, the interpretation and application of these results should take full cognisance of some potential shortfalls. The identification of drought tolerant genotypes was based on above-ground characteristics only,

Application of key findings and opportunities for commercialisation and future directions for cowpea research in Malawi

without examining the root characteristics, which also play a critical role in defining drought tolerance. The identification of root characteristics would strengthen the validity of tolerance levels of the drought tolerant genotypes. Results from the field experiments conducted over one season provide insights into the existence of high yielding and well-adapted genotypes. However, repeated experiments over several seasons and sites would strengthen the validity of the results, more especially on yield related characteristics, which are easily affected by the environment. Farmers’ selection of genotypes was applicable to the characteristics used in this study only. Other important attributes, such as cooking time and palatability characteristics, which were not considered in this study, also play a pivotal role in determining preferred varieties. Consequently, more work needs to be undertaken with farmers, with respect to cooking and palatability tests. Disease and pests resistance of the genotypes with desirable attributes is not well understood. Therefore, more research is required to comprehend the pests and disease resistance of these genotypes. In the absence of knowledge on pests and disease resistance of these genotypes, their production should be accompanied with appropriate plant protection practices that target the most important pests and diseases.

The assessment of drought tolerance at vegetative stage only in this study is a great drawback to application of results for future cowpea improvement. Cowpea suffers significant yield

reduction when stressed at reproductive stage (Hall et al., 2003; Belko et al., 2014).

Therefore, assessment of drought tolerance at vegetative stage only rather than reproductive stage (flowering and pod set) provided limited understanding of effect of drought on yield of the evaluated germplasm. Cowpea germplasm which showed drought tolerance at vegetative stage in this study should be further tested at both reproductive for the identification of genotypes with high yield potential under drought conditions.

This research takes full cognisance of inadequate germplasm (low numbers of genotypes) included in the study which may result in a breeding program being started using germplasm that is not best available. Several factors contributed to the low numbers of genotypes included in all the experiments. Prior to set up of the first glasshouse experiment all the sixty- six accessions from Malawi reported in Chapter 3 were quarantined for biosecurity assessment. Forty accessions passed the assessment and were recommended for inclusion into the first glasshouse experiment. However, due to limited space in the available glasshouses at the Plant Growth Unit (PGU), only thirty six accessions were included in the first experiment. Results from the first glasshouse experiment defined the number of genotypes in the subsequent two experiments except for two released varieties (Sudan 1 and IT82E16) which were included in the field experiment conducted in Malawi. This shortfall requires further research to survey available genetic variability in the elite backgrounds including those from IITA and other research institutions.

8.5 Conclusions

The goal of this study was to explore the presence of cowpea genotypes with drought tolerance, high yield and other desirable attributes among local germplasm conserved at the Malawi Plant Genetic Resources Centre (National Genebank of Malawi). One of the significant results emerging from the study is the identification of genotypes with different responses to drought; drought avoidance (479, 601, 645 and 2226) and drought tolerance (3254). The second major finding is the development of a leaf wilting index, which will contribute to an improved scoring system for wilting in cowpea and related crops. In addition to drought tolerant genotypes, the research has also identified genotypes with other desirable attributes. Firstly, Sudan 1 was preferred for high yields at various sites, while 3254 yielded highly in areas with low rainfall and high temperature. Secondly, genotypes 305 and 309 scored high for early maturity and high pod load, a characteristic liked specifically by farmers

Application of key findings and opportunities for commercialisation and future directions for cowpea research in Malawi

for the production of vegetable (immature fresh pods) cowpea. Thirdly, 2226 and 2227 showed large seeds. Finally, 2226, 645 and 2227 were preferred for late maturity and high leaf biomass, a characteristic suitable for the production of high value forage and leaves for human consumption. The presence of multiple desirable attributes provides support for the conceptual premise that well adapted and preferred cowpea varieties can be developed from the available germplasm.

Undesirable characteristics were identified in some genotypes. Genotype 2232 showed wilting signs within the first week of stress suggesting poor performance under low rainfall and high temperature conditions. Genotype 3254 was poorly ranked by farmers due to its wrinkled seeds potentially limiting its utilisation by small growers for domestic use. However, this genotype is potentially useful for commercial production targeting the processing industry. A comprehensive breeding programme is required, in order to improve these undesirable characteristics, without compromising the positive attributes of the two genotypes.