RAPD technique was used as a tool for assessing genetic diversity and varietal relationships among ten varieties of eggplant. Out of 21 primers screened four were selected. With these primers 76 clear and bright fragments were obtained of which 44 fragments considered polymorphic. The proportion of polymorphic loci and gene diversity values across all loci were 57.89% and 0.23, respectively. The UPGMA dendrogram based on genetic distance segregated the ten varieties of eggplant into two main clusters. Dohazari, Kazla, Nayantara and ISD-006 were grouped together in cluster I whereas Uttara, Islampuri, Khatkhatia, Singnath, BARI Begun-08 and Eggplant Line-083 into cluster II. Kazla and Nayantara variety pair was very close to each other with the highest intervarietal similarity index (92.54%) and lowest genetic distance (0.14). On the other hand, Khatkhatia and Nayantara pair was the lowest intervarietal similarity index (41.67%) with highest genetic distance (0.48). Therefore, identification of genetically distinct varieties using RAPD markers could be a potential tool for eggplant improvement.
In Bangladesh, the third largest producer of potatoes in Asia, late blight, caused by Phytophthora infestans, is the major constraint to production. Nevertheless, there is a lack of published information on the pathogen population. A collection of 69 isolates obtained from samples of infected potato foliage collected in 2018–2019 varied significantly in their aggressiveness to detached potato leaflets and tuber slices of cv. Diamant. On leaflets, most isolates were highly aggressive, colonizing more than half the surface in 7 days. On tuber slices, while some isolates were highly aggressive, those collected in 2019 were less so. There was a significant effect of the locations from which the isolates were obtained on aggressiveness to both leaflets and tuber slices, but aggressiveness to leaflets and to tuber slices was not significantly correlated. All isolates were A2 mating type and either intermediate (38%) or resistant (62%) in sensitivity to the fungicide metalaxyl. A subset of 24 isolates all had mitochondrial DNA haplotype Ia.Samples of P. infestans DNA (124) from infected potato foliage obtained from Bangladesh (2014–2019) were genotyped by 12-plex SSR. The vast majority (95%) were assigned to EU_13_A2, which was present in every year in which samples were collected. Numerous EU_13_A2 variants were identified, many specific to Bangladesh. Six samples (from 2017 to 2019) had genotypes distinct from EU_13_A2 and with no close match to known European lineages. It is concluded that the current P. infestans population of Bangladesh is dominated by the aggressive lineage EU_13_A2, also dominant in India and Pakistan. The implications of this for control of late blight are discussed.
Wheat production in many countries is threatened by climate change and rising sea levels causing increases in salt‐water intrusion in low‐lying coastal areas. Large areas of the coastal zone of Bangladesh remain fallow during the dry season primarily due to salinity. It is estimated that 0.86 million hectares of land currently under fallow in the dry season would be suitable for wheat production using varieties with enhanced salt tolerance. This study investigated the impact of salt tolerance Nax genes (Na+ exclusion) on the grain yield of bread wheat grown on saline soils in southern Bangladesh. Nax1 and Nax2 genes were separately crossed into two Bangladeshi bread wheat varieties, BARI Gom 25 and BARI Gom 26, through conventional crossing with marker‐assisted selection. The key outcome was strong evidence that both Nax genes have the capacity to lower leaf Na+ concentration in locally adapted bread wheat and consequently deliver improved yields in challenging field environments in southern Bangladesh with moderate to high salinity. The genetic backgrounds of the adapted varieties played a significant role in the expression of these genes. There was a differential response in the phenotypic expression of Nax genes to reduce leaf Na+ levels between the two local varieties selected as recurrent parents and the resultant variation in yield. The average reduction in leaf Na+ concentrations from the third backcrossed lines in the BARI Gom 25 background was about twice that of lines in the BARI Gom 26 background. These same lines typically yielded between 10% and 20% higher than BARI Gom 25 on moderate to high salinity sites, whereas the backcrossed lines in the BARI Gom 26 background yielded similarly to their recurrent parent at these same sites. The contrast in the differential phenotypic expression of the Nax genes evident in the two recurrent parents represented in this study highlights the importance of crossing salt tolerance Nax genes into a range of locally adapted high‐yielding genetic backgrounds to identify the greatest potential for improvement in salt tolerance.
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