Fagopyrum 23: 23-27 (2006) A diversity in qualitative traits of Nepalese cultivated buckwheat species Bal Krishna JOSHI* and Bimal Kumar BANIYA Nepal Agricultural Research Council, Khumaltar, PO Box 1135, Kathmandu, Nepal Received February 5, 2006; accepted in revised form October 9, 2006 Key words: Diversity index, qualitative traits, Tartary buckwheat, common buckwheat ABSTRACT Quantifying the qualitative variation of buckwheat species is necessary for breeding work and managing crop genetic resources effectively. Three diversity indices, namely Shannon-Weaver index, Evenness and Simpson's index were calculated for 15 qualitative traits observed in 302 common and 150 Tartary buckwheat accessions which were collected from different areas of Nepal and evaluated on station. These indices were also estimated for landraces of Tartary buck- wheat observed on farms. Nepalese farmers distinguish buckwheat species and landraces easily based on qualitative traits. However, a single qualitative trait was not enough to distinguish these species. For that identification growth habit, flower stalk color, flower color and seed surface were useful. Average values of these diversity indices were higher in common than in Tartary buckwheat; however, all the traits of common buckwheat were not more diverse than Tartary buckwheat. Diversity of reproductive traits was higher than for vegetative parts. The highest variation in common and Tartary buckwheat was noticed in flower color and seed color, respectively. found in Tartary buckwheat. Among the different measures of diversity, Shannon- Weaver (H'), Evenness (E) and Simpson's index (D) are being used for qualitative traits (Tolbert et al., 1979; Holcomb et al., 1977; Niwranski et al., 2002; Sullivan et al., 1998). where, H', Shannon-Weaver index; E, Evenness; D, Simpson's index; pi, the proportion of entries in the i th class of an n-class trait. H' includes both species number and evenness, where a greater number of species increase diversity, as does a more equitable distribution of indi- viduals among species. Evenness is a measure of the relative abundance of the different species making up the richness of an area. A community dominated by one or two species is considered to be less diverse than one in which several different species have a similar abundance. As species richness and evenness increase, so diversity increases. E describes the equitability or evenness of indi- vidual distribution among populations. Its value range from oto 1, with 1 being complete equitability. Simpson's index is a measure of diversity, which takes into account both richness and evenness. The value of D also ranges between o and 1, the greater the value the greater the sample diversity. Simpson' s index gives more weight to the more abundant species in a sample. The addition of rare species to a sample cause only small changes in the value of D. This measure has been used to describe variation in INTRODUCTION Two species, common (Fagopyrum esculentum Moench) and Tartary (F. tataricum Gaertn.) buckwheat are cultivated in the mid and high hills of Nepal. These areas are food deficit and do not have transportation and electricity facilities. Therefore improvement on buckwheat will greatly help to make food self-sufficiency in those areas. The availability of diversity and heritability of traits may determine the success of conventional breeding which is a simple and common method for buckwheat improve- ment. A study on the highly heritable traits e.g. qualita- tive traits is useful in shaping breeding approaches . Diversity exists in Nepalese landraces of these two buckwheat species in terms of growing seasons, cultural practices, adaptability to different environments and agro- morphological traits which are necessary to fulfill the di- verse needs of the farmers. Betweenthe two species,Tartary buckwheat has a yield advantage over common buck- wheat. Among the important traits assessed by Sherchand and Ujihara (1995), plant height and number of flower clusters expressed the highest deviation from the mean value. These variabilities were found to be maximum in the strains collected from Mustang, Nepal. A study at the agromorphological , biochemical and molecular levels showed that variation is higher in wild species than in cultivated ones. When compared between the two culti- vated species, common buckwheat shows more diversity than does Tartary buckwheat. However , diversity in com- mon buckwheat may not be higher in all traits than that * Corresponding author. E-mail: joshibalak@rediffmail.com 23 H'=- I pi log. pi , i=! D=l - IP1 '2 . i= l