Pod characters
Pod initiation was significantly early in released variety Arka Sharadh (31.66 days), followed by local variety Selection (33.33 days), EC530843 (33.66 days) and IC540876 (37.33 days) than other varieties. Average days taken for pod initiation were 38.73 days. Pod length was significantly higher in Arka Komal, EC559574 and pod width found significantly higher in IC540876 and EC530842 than other accessions. Average dry pod weight per plant was 40.47 g. Higher dry pod weight per plant was observed in IC342273 (58.94 g) than released variety Arka Komal (52.64 g). Higher number of pods per plant were found both in IC342273 (40.33) and IC540876 (33.33) is higher than average number of 22.34 pods (Table 1). Thus, accessions
viz., EC530843, IC540876, EC559574, EC530842 and IC342273 can screened for pod characteristics as they were on par with released varieties.
Rana et al., (2015) reported similar results.
Seed characters
Average number of seeds per pod was 4.81, however, in accessions EC530843 and IC405546 found significantly higher number of seeds per pod (6.33). Seed breadth and length was higher in accessions IC11676 and IC405546, which were on par with Arka Sharadh and Arka Suvidha. Yield parameters
viz., total pod and seed yield per plot was found to be significantly higher in the accessions IC342273, EC531078 and IC328655 than other accessions. Crop duration was more in released variety Arka Suvidha followed by EC530819 and EC304657 (Table 2).
Dass et al., (2014) and
Rana et al., (2015) reports similar results. Further exploitation of the accessions with higher seed and pod yield traits will results in identifying the good quality of varieties.
Estimation of seed micronutrient (Fe, Zn, Mn and Cu) contents
Among twenty-four bean accessions analysed, the mean Fe content was 159.25 ppm. The accession IC538420 (177.31 ppm) showed significantly higher level of Fe content followed by released variety Arka Suvidha (175.98 ppm), EC530886 (173.67 ppm) and IC342273 (170.02 ppm). Lower level of Fe content was recorded in accessions IC328655 (139.90 ppm), Arka Anoop (143.86 ppm), IC329154 (148.30 ppm) and IC311676 (149.95 ppm) (Fig 1). Ability of genotypes to absorb and accumulate Fe depends on genetic potential, soil and agro climatic condition of place where the genotypes are grown.
Beebe et al., (2000) have made similar reports in Andean and Mesoamerican gene pools of bean. Similarly, in present study Fe content ranged from 139.90-177.31 ppm, where wild accessions and released varieties exhibited a difference of 20-25 ppm of Fe accumulation.
The evaluation of twenty bean accessions and four released varieties for Zn content revealed a range of 20.23-26.91 ppm with an average value of 23.73 ppm. Accessions with significantly higher Zn content were found in EC500226 (26.91 ppm), EC530843 (26.85 ppm), EC530819 (26.49 ppm), released variety Arka Sharadh showed 25.03 ppm and lower level of Zn content in accessions EC559576 (20.23 ppm), IC329154 (21.71ppm) and IC342273 (21.90 ppm) (Fig 2). Similar reports were made by
Beebe et al., (2000); Blair et al., (2009); Golam et al., (2011).
Manganese content varied significantly, with a range of 5.23-15.31 ppm and mean Mn content was 8.46 ppm. Accession with significantly higher Mn content were found in EC500226 (15.31 ppm), IC538420 (11.83 ppm), EC530819 (10.78 ppm), EC530842 (10.25 ppm), released varieties Arka Sharadh (8.77 ppm), Arka Komal (8.65 ppm) (Fig 2) and lower level of Mn content in accessions IC329154 (5.23 ppm) and IC311676 (5.98 ppm). Similar reports were made by
Beebe et al., (2000); Brigide et al., (2014).
Copper content ranged from 3.71-8.55 ppm with an average of 6.17ppm. The accession with recorded higher Cu content were EC500226 (8.55 ppm), EC531078 (8.40 ppm), EC304657 (7.98 ppm) and among released varieties, Arka Sharadh showed significantly higher Cu content (7.19 ppm). Whereas released varieties Arka Komal (3.71 ppm), Arka Anoop (4.30 ppm), Arka Suvidha (4.76 ppm) and accession IC538430 (4.26 ppm) had found lower Cu content compared to other released varieties accessions (Fig 2). Present study revealed higher concentration of Cu in accessions compared to released varieties. Similar reports were made by
Beebe et al., (2000); Giuseppa et al., (2016).
Micronutrient contents are higher in the wild types compared to released varieties, due to the ability of genotypes to absorb and assimilate micronutrients into seeds, also the factors like soil and environments plays a major role
(Beebe et al., 2000).
Molecular screening of French bean accessions using SSR markers linked to Fe and Zn content
Among fourteen SSR markers, twelve SSR primers have given good scorable loci out of which genomic SSR marker BM154 has detected polymorphic loci in eleven accessions (EC500226, EC530819, EC530842, EC530843, EC530886, EC559574, EC559576, IC342273, IC538420, IC540876 and Arka Komal) with expected amplified product size of 218 bp and present on linkage group b09 amplified. These eleven accessions having green pods and brown seeds have Polymorphism Information Content (PIC) of 0.18.
Another genomic SSR marker BM211 depicted high polymorphism among the twenty-four bean accessions studied and is considered for Fe content present on linkage group b08. The ten polymorphic loci has detected in ten accessions (EC500226, EC530819, EC530842, EC530843, EC530886, EC559574, EC559576, IC342273, IC538420 and Arka Komal) with expected amplified product size of 186 bp (Fig 3). These accessions had green pods and brown seeds with PIC of 0.37 as PIC analysis used to evaluate the markers; it helps in selecting the most appropriate one for genetic mapping, phylogenetic analysis or association genetics
(Anderson et al., 1993). Average number of alleles and PIC detected were 109 and 0.16 respectively. The Genomic SSR markers showed good polymorphism than gene based SSR markers.
Blair et al., (2011) reports similar results as they revealed that the gene based microsatellites were frequently bi-allelic or tri-allelic along with spotting the difference between various gene pools. Whereas most of the genomic microsatellites detected, reveled more than three alleles and were able to resolve within gene pool variations
(Schloss et al., 2002).
Dendrogram for Fe and Zn diversity in French bean accessions
To understand the genetic relationship among bean accessions and cultivars, heirarchial cluster analysis with Unweighted Pair group-average (UPGMA) clustering method following Sequential Agglomerative Hierarchial Nested (SAHN) cluster analysis module was performed using software NTSYS 2.20. Based on the seed Fe and Zn accumulation, cluster analysis separated the twenty-four accessions into two interrelated clusters namely Major Cluster-I with one accession (EC531078) and Major Cluster-II with remaining twenty-three accessions and varieties (Fig 4). Further major cluster-II was sub divided as sub cluster-I with nine accessions and three released varieties (EC500226, EC500474, IC538430, Selection, IC328655, IC311676, IC405546, IC540876, IC329154, Arka Sharadh, Arka Suvidha and Arka Anoop) and sub cluster-II with ten accessions and one released variety (EC304657, EC512812, EC530843, EC530819, EC530842, EC530886, EC559574, IC342273, EC559576, IC538420 and Arka Komal). It has also revealed that three released varieties (Arka Anoop, Arka Sharadh and Arka Suvidha) showing close linkage with many accessionsin sub cluster-I of Major Cluster-II. Similarly, Arka Komal variety is showing close relation to many accessions in sub cluster-II of Major Cluster-II. It was found that either there was no correlation between morphological characteristics or micronutrient content with accessions grouped in sub clusters-I and II.
Blair et al., (2009) made similar kind of observations.