In East Africa, Napier grass (Pennisetum purpureum) is a perennial grass grown widely as a fodder crop and feed for the cut-and-carry zero-grazing dairy systems and constitutes up to 80 % of forage for smallholder dairy farms. It is the forage of choice not only in the tropics but also worldwide due to its desirable traits such as tolerance to drought and a wide range of soil conditions, and high photosynthetic and water-use efficiency. While much attention has been directed towards research for improving the productivity of major cereal crops, there has been comparatively little effort to improve Napier grass, an important forage crop that has been grown over centuries and currently enjoys a multiplicity of uses besides conventional animal consumption. This is key among the drivers of renewed research interest in this otherwise previously neglected crop. However, the productivity of Napier grass is limited by several factors especially emerging diseases, mainly Napier grass stunt disease and Napier grass head smut disease, which constrains the growth of the smallholder dairy industry. For this reason, it is necessary to strengthen forage breeding programmes for the development of disease-resistant cultivars.
Correct identification of Napier grass accessions is a prerequisite because the existing germplasm information is scanty and cannot be relied upon for crop improvement, since cultivar discrimination has predominantly relied on morphological and agronomic features and is the major cause of inconsistency in identification. Consequently, a number of Napier grass cultivars have been in circulation, often with more than one name. Molecular markers have proven useful in distinguishing among morphologically related individuals within cultivars of the same plant species. Thus the genetic assessment of various Napier grass accessions from the Eastern Africa region is important for correct cultivar identification in order to exploit them fully in crop improvement strategies.
A new study in AoB PLANTS assessed the genetic variation between and within Napier grass collections comprising 281 accessions from selected regions in Eastern Africa (Kenya, Uganda, Tanzania and Ethiopia). The methodology developed in this study was able to discriminate among different Napier grass accessions and could be useful in screening cultivars.
Genetic diversity in Napier grass (Pennisetum purpureum) cultivars: implications for breeding and conservation (2013) AoB PLANTS 5: plt022 doi: 10.1093/aobpla/plt022
Napier grass is an important forage crop for dairy production in the tropics; as such, its existing genetic diversity needs to be assessed for conservation. The current study assessed the genetic variation of Napier grass collections from selected regions in Eastern Africa and the International Livestock Research Institute Forage Germplasm-Ethiopia. The diversity of 281 cultivars was investigated using five selective amplified fragment length polymorphism (AFLP) markers and classical population genetic parameters analysed using various software. The number of bands generated was 216 with fragments per primer set ranging from 50 to 115. Mean percentage polymorphic loci was 63.40. Genetic diversity coefficients based on Nei’s genetic diversity ranged from 0.0783 to 0.2142 and Shannon’s information index ranged from 0.1293 to 0.3445. The Fst value obtained was moderately significant (Fst = 0.1688). Neighbour-joining analysis gave two distinct clusters which did not reflect geographical locations. Analysis of molecular variance showed all variance components to be highly significant (P < 0.001), indicating more variation within (91 %) than between populations (9 %). Results suggested moderate genetic differentiation among Napier grass populations sampled, which could imply a high germplasm exchange within the region. The AFLP markers used in this study efficiently discriminate among cultivars and could be useful in identification and germplasm conservation.