Acid lime (Citrus aurantifolia (Christm.) Swingle) is an important fruit crop, which has high commercial value and is cultivated in 60 out of the 77 districts representing all geographical landscapes of Nepal. A lack of improved high-yielding varieties, infestation with various diseases, and pests, as well as poor management practices might have contributed to its extremely reduced productivity, which necessitates a reliable understanding of genetic diversity in existing cultivars. Hereby, we aim to characterize the genetic diversity of acid lime cultivars cultivated at three different agro-ecological gradients of eastern Nepal, employing PCR-based inter-simple sequence repeat (ISSR) markers. Altogether, 21 polymorphic ISSR markers were used to assess the genetic diversity in 60 acid lime cultivars sampled from different geographical locations. Analysis of binary data matrix was performed on the basis of bands obtained, and principal coordinate analysis and phenogram construction were performed using different computer algorithms. ISSR profiling yielded 234 amplicons, of which 87.18% were polymorphic. The number of amplified fragments ranged from 7–18, with amplicon size ranging from ca. 250–3200 bp. The Numerical Taxonomy and Multivariate System (NTSYS)-based cluster analysis using the unweighted pair group method of arithmetic averages (UPGMA) algorithm and Dice similarity coefficient separated 60 cultivars into two major and three minor clusters. Genetic diversity analysis using Popgene ver. 1.32 revealed the highest percentage of polymorphic bands (PPB), Nei’s genetic diversity (H), and Shannon’s information index (I) for the Terai zone (PPB = 69.66%; H = 0.215; I = 0.325), and the lowest of all three for the high hill zone (PPB = 55.13%; H = 0.173; I = 0.262). Thus, our data indicate that the ISSR marker has been successfully employed for evaluating the genetic diversity of Nepalese acid lime cultivars and has furnished valuable information on intrinsic genetic diversity and the relationship between cultivars that might be useful in acid lime breeding and conservation programs in Nepal.

The air quality of the Kathmandu valley is highly degraded by pollution from motor vehicles. Planting green vegetation along roadsides has been shown to reduce air pollutants. Different leaf parameters like pH, relative water content, chlorophyll content, and ascorbic acid content, that comprise the Air pollution tolerance index (APTI), were used to test the susceptibility of plants to air pollution. APTI values of ≤11, 12–16, and ≥17 categorised the plant species under sensitive, moderate, and tolerant species, respectively. In the present study, all the plant species had APTI less than 11. The highest APTI value was for Mangifera indica (10.62) and the lowest for Buddleia asiatica (6.92). Therefore, based on the findings of the present study, planting trees with high APTI value alongside the roads may help reduce air pollution as these trees are resistant to high pollution levels.

Acid lime (Citrus aurantifolia Swingle) is an important commercial fruit crop, cultivated from terai to high hill landscapes of Nepal. However, production and productivity is very low due to various reasons including infestations by various diseases and pests, lack of diseases and pests resistant and high yielding varieties. In this context, determination of genetic variation at molecular level is fundamental to citrus breeders for the development of elite cultivars with desirable traits. In the present study, Random Amplified Polymorphic DNA (RAPD) marker technique has been employed to assess genetic diversity in 60 acid lime landraces representing different agro-ecological zones of eastern Nepal. Nine selected arbitrary primers generated 79 RAPD fragments of which 75 were polymorphic (94.94%). Phenogram was constructed by NTSYSPC ver. 2.21i using UPGMA cluster analysis based on Jaccard’s similarity coefficient to deduce overall genetic diversity and relationships of the acidlime genotypes under study. Sixty acid lime landraces formed seven clusters and similarity value ranged from 38% to 98% with an average of 72%. Genetic variation at different agro-ecological zones was assessed using Popgene ver. 1.32 and found 47% to 69.6% polymorphism. Shannon’s index and Nei’s gene diversity showed highest level of acid lime diversity in Terai zone (PPB, 69.62%; H, 0.213; I, 0.325) followed by mid-hill zone (PPB, 67.09%; H, 0.208; I, 0.317). The results obtained will be useful to citrus breeders for elite cultivar development. The RAPD-PCR technique is found to be the rapid and effective tool for genetic diversity assessment in acid lime landraces of Nepal. DOI: http://dx.doi.org/10.3126/ijasbt.v2i3.10950 Int J Appl Sci Biotechnol, Vol. 2(3): 315-327