EVALUATING THE STABILITY AND ADAPTABILITY OF BAMBARA GROUNDNUT (VIGNA SUBTERRANEAN (L.) VERD.) LANDRACES IN DIFFERENT AGRO-ECOLOGIES

Bambara groundnut has been planted in Indonesia for hundreds of years. Researchers have evaluated where the Indonesian Bambara groundnut landraces were introduced from but no-one has evaluated the stability and adaptability of Bambara groundnut in Indonesia. Thirty-six landraces were planted in Indonesia, together with putative Indonesian × African hybrids and their offspring. These were assessed for their stability and adaptability by the methods of Finlay and Wilkinson (1963) and Eberhart and Russel (1985). Results from seven landraces are presented. The seven landraces were: ‘LunT’ from Sierra Leone; ‘AHM753’; ‘SB165A’ and ‘S19-3’ from Namibia; ‘DODR’ from Tanzania; ‘Uniswa Red’ from Swaziland; ‘DIPC’ from Botswana; and the Indonesian landrace ‘Gresik’ as control. Thirty plants of each landrace were planted in a randomised block design with three replicates at Gresik, Bojonegoro and Jatikerto in Indonesia in November 2009. Each location had a different altitude, soil type and rainfall. Gresik is the main Bambara groundnut growing region in the East of Java, Indonesia. Prior to this experiment, farmers in Bojonogoro and Jatikerto were not familiar with this crop. Many traits were assessed based on the list of descriptors of Bambara groundnut issued by IPGRI, but in this report we present only the results of stability and adaptability analysis for 50% flowering, days to maturity, pod number per plant and the 100 seeds weight traits. Analysis of variance showed highly significant differences in all three locations and combined analysis of variance over sites (Gomez and Gomez, 1983) indicated that location, landraces and location × landraces interaction are substantially different (1%). Stability and adaptability parameters were obtained as the linear regression coefficient (bi) of the mean of all data observed and deviation from the regression analysis (Sdi) with the hypothesis that bi=1 and Sdi=0. The results indicated that almost all landraces observed were stable, but only three landraces revealed good adaptability in all three locations, namely ‘SB165A’, ‘Uniswa Red’ and ‘DIPC’. Meanwhile ‘LunT’ and ‘S19-3’ are considered promising landraces because they are well adapted in two of the four variables used. This information could prove useful for breeding programmes. INTRODUCTION Bambara groundnut is not a native crop of Indonesia. Records suggest that it came from South-West Africa in the early 18 century, through trade links. The seed coat has numerous colours namely: brown, cream, red, black or variegated testa. Due to farmers selectively planting certain colours, the colour of seed testa planted in Indonesia today is largely black, dark red, dark brown and dark purple. Indonesian farmers prefer to plant seed having dark coloured testa and a white hilum. Nutritional content of this crop is comparable to other legumes. Linnemann and Azam-ali (1993) estimated that the protein content of Bambara groundnut was between 16-25%. This legume crop is suitable for semi-arid climates, is relatively resistant to Proc. 2 Int. Symp. on Underutilized Plants Species “Crops for the Future – Beyond Food Security” Eds.: F. Massawe et al. Acta Hort. 979, ISHS 2013 390 diseases and pests (Linnemann and Azam-ali, 1993) and has the potential to generate high yields (Collinson et al., 2000). Even though this crop is broadly distributed in Africa and South East Asia, until recently Bambara groundnut did not receive appreciable research efforts, particularly for genetic improvement (Massawe et al., 2005) so Bambara groundnut currently exists as landraces rather than cultivars, which significantly complicates genetic analysis and breeding. However, it may assist crop survival under harsh environmental conditions (Zeven, 1998). Most researchers working on Bambara groundnut (Karikari, 2000; Basu et al., 2007; Mwale et al., 2007; Ntundu et al., 2006) consider it to have many useful traits for crop improvement. In a study of 27 genotypes under optimal agronomic conditions in Ghana (Karikari, 1972), a simple correlation analysis indicated that number of stems per plant and 100 seeds weight were positively correlated with grain yield and these characters were used for selection. The characterisation and evaluation of Bambara groundnut at the International Institute of Tropical Agriculture (IITA) revealed enormous agromorphological diversity which could be used for crop improvement. In a correlation matrix study of the IITA collection, Goli et al. (1997) found that the characters most strongly correlated with grain yield were number of leaves, pods, shell thickness and 100 seeds weight. Karikari (2000) found that 100 seeds weight was the most important character to consider during selection and breeding of Bambara groundnut in Botswana and areas with similar climates. Masindeni (2006) also showed that seed number per pod and 100 seed weight had a highly positive correlation to grain yield. In contrast, Misangu et al. (2007) found that there was a negative correlation between 100 seeds weight and pod number of Bambara groundnut in a screen house experiment in Tanzania. They also suggested that early flowering of landraces could represent an advantage in terms of forming pods for a longer period of time to generate more pods, while late flowering resulted in a decrease in the seed yield. Another experiment in Nigeria (Jonah et al., 2010) found a positive genotypic correlation between seed and pod number per plant. Makanda et al. (2009) have suggested that pod number per plant should be an important trait in the further development of Bambara landraces. Some landraces may give good performance in a specific environment, but poor in others. The ability of some crops to perform well phenotypically across a wide range of environmental conditions has been examined by plant breeders and agronomists. Allard and Bradshaw (1964) considered that the stability of landraces is a reflection of their adaptability to environmental changes. A landrace may be stable across environments if it gives limited deviation in response to different environments (Becker and Leon, 1988). Finlay and Wilkinson (1963) characterised the stability of landraces based on a regression coefficient (bi) with the following classification: bi=0, absolute stability; bi=1, average stability; bi<1, above average stability and bi>1, below average stability. Moreover Eberhart and Russel (1966) examined adaptability which correlated bi and mean yield. A landrace which has a regression coefficient (bi) of 1 would, in general, be said to be adaptable. However, when general adaptability is correlated with a high mean yield, it can be said to be well adapted. Moreover, it can be said to be poorly adapted when correlated to a low mean yield. A landrace which has above average mean yield in an unfavourable environment, but is low yielding in a good environment, can be said to have a specific adaptability to that unfavourable environment, and vice-versa for a landrace with a specific adaptability to a favourable environment. The current problem of Bambara groundnut in Indonesia is that it has a long life span and is low yielding (<1 t ha). Even though it has a high market price, farmers are reluctant to plant it because of the time to maturity. Thus a new cultivar with desirable traits, such as high yielding and quick maturing, is needed, even though it may be difficult to achieve both at the same time. Several field experiments were conducted in Indonesia to assess the desirable traits of Bambara groundnut for development of a potential new cultivar. The aims and objectives of this project were to evaluate Bambara groundnut landraces under Indonesian conditions. Selected Bambara groundnut landraces were