Landraces (LRs) are important as a source of novel alleles for crop improvement, and their conservation is therefore necessary for food security. These genetic resources have suffered continuous erosion, especially in more accessible areas. We assess the loss of Nepali rice LRs and identify the factors influencing the probability of cultivating the most dominant LR via a logistic regression model. The majority of farmers cultivate LRs and modern varieties simultaneously. However, there has been a decrease in varietal diversity and a loss of some LRs over recent years, mainly because of their low yield, their sensitivity to diseases and pests, and their late maturity. The opportunity cost of maintaining the Satha landrace is higher on irrigated farms and for those farmers specializing in niche products. On the other hand, Satha is more likely to be cultivated by large-scale farmers and by those having a religious and/or a cultural attachment to this LR. Market-based incentives are less costly than publicly funded conservation programmes, and the superior taste of some LRs may allow them to be developed as niche products. However, to achieve this, public investment is needed to generate the necessary support infrastructure. In the more accessible Terai region, there is a particular need to introduce a flexible incentive mechanism to maintain LRs and to offset the negative effect of development intervention.

With the numbers of new varieties of potato obtaining Plant Breeders' Rights increasing yearly, the reliable maintenance of large culture collections is becoming more problematic. Additionally, the differentiation of cultivars based on morphological characteristics is a highly skilled and time-consuming task and for these reasons a rapid and robust method for variety differentiation has become highly desirable. By screening a number of microsatellite (simple sequence repeat, SSR) markers we have developed a set of six that can be used to differentiate over 400 cultivars, including those on the UK National List, but excluding somaclonal variants (e.g. Red King Edward and King Edward). The whole process from tuber to accurate identification can be carried out in a single day.

The Dilatata group of Paspalum is a polyploid complex native to the grasslands of temperate South America. A pentaploid apomictic biotype of P. dilatatum is a widely recognized forage grass; however, the complex includes apomictic tetra- and hexaploids along with sexual allotetraploids (P. urvillei, P. dasypleurum, P. dilatatum ssp. flavescens, and biotypes Virasoro and Vacaria of P. dilatatum) which are suspected to be hybrids between different combinations of biotypes. Fifteen primer pairs for nuclear microsatellite loci were developed from a (CA)n-enriched genomic library. A single, low stutter, robust two-step PCR profile was used for all the primer pairs. Twelve primer pairs were analysed for their variability and transferability among all the sexual biotypes of the Dilatata group and the common apomictic pentaploid. Six primer pairs amplified more than one locus, and sequence and segregation evidence suggest that the additional bands correspond to homeologous loci. No close linkage was found among the 16 loci amplified in the tetraploids. One variable chloroplast microsatellite is also reported. All loci were successfully amplified from most members of the Dilatata group and variability was recorded for all the biotypes analysed. The set of loci reported here provide highly variable markers for intra-biotypic population studies, biotype-specific markers for the analysis of hybrid apomicts and a biotype-specific chloroplast marker.

Groundnut is one of the most important oilseed crops in the world. Bacterial wilt, caused by Ralstonia solanacearum E. F. Smith, is one of the major biotic constraints to groundnut production particularly in South-East Asia and East Africa. Several sources of resistance to bacterial wilt have been identified through field screening of groundnut germplasm. The aim of the present study was to quantify the genetic diversity among selected bacterial wilt-resistant lines, in comparison with the levels of variation observable within the cultivated A. hypogaea gene pool. Thirty-two SSR markers were used to assess the degree of molecular polymorphism between 46 selected genotypes revealing 107 alleles, of which 101 (99.4%) were polymorphic with gene diversity scores ranging from 0.103 to 0.669, averaging 0.386. Cluster and multidimensional scaling analysis revealed two distinct groups within the germplasm broadly corresponding to the two subspecies (hypogaea and fastigiata) of A. hypogaea. However, accessions of varieties peruviana and aequatoriana grouped together with the varieties from subsp. hypogaea, rather than grouping with the other varieties of subsp. fastigiata. Analysis of molecular variance (AMOVA) revealed that 15% of the total observed variation was accounted for by disease response groups. This analysis will be useful in the selection of parental genotypes for mapping populations and breeding programmes attempting to broaden the genetic base of future groundnut cultivars. In particular, this opens up significant opportunities for the development of intraspecific mapping populations that will be highly relevant to modern groundnut breeding programmes.

The composition of essential oils obtained from leaves of Acorus calamus growing wild in 19 different locations was analysed by gas chromatography and gas chromatography–mass spectrometry. In total, 84 constituents have been identified, representing at least 86% of the total essential oil. The essential oils were dominated by the presence of phenolic compounds: (Z)-asarone (15.7–25.5%) and (Z)-methyl isoeugenol (2.0–4.9%). Other identified major components were (E)-caryophyllene, α-humulene, germacrene, linalool, camphor and isoborneol. All oils were found to have a similar composition. However, a hierarchical cluster analysis of the quantitative data revealed significant differences between some accessions. Minimal inhibitory concentrations (MIC) of four selected leaf essential oils were determined by a screening test with the broth dilution method. Of the 17 species of fungi, bacteria and yeasts tested, Mycobacterium ssp. and Bacillus subtilis were most susceptible to essential oils. Oils displayed low anti-fungal activity and their inhibitory activity was lower than the standard antibiotics. Oils differed in their activities against the various microorganisms tested.

Genetic resource conservation is widely acknowledged as important. The implementation of conservation requires an insight into the distribution of genetic diversity at the scale of small regions or villages. We present an analysis of rice diversity at such a scale, in a region where traditional farming still prevails. Regional allelic diversity was comparable to that noted worldwide for Asian rice (Oryza sativa), but not as high for African rice (O. glaberrima). Each village pooled more than half of the regional allelic diversity. Genetic differentiation between varieties from the same village accounted for 70% of the regional variation. The differentiation associated with lowland and upland rice-growing ecosystems was 23%, while that associated with differences between villages within the same ecosystem was 7%. In the upland ecosystem, geographical distance had a significant effect on the FST between pairs of villages. In the lowland ecosystem, differences in soil salinity between villages affected FST. Genetic diversity within a single village may have up to three components: an ancient glaberrima component shared with neighbouring or ethnically related villages; a relatively ancient sativa component which was hardly or no longer shared with other villages due to local differentiation; and a recently introduced sativa component shared with other villages. Genetic resource conservation could be achieved, in terms of allelic diversity, through stratified sampling according to described genetic differentiation factors, whereas current farming systems must be preserved to ensure conservation of the diversity of allelic associations.