Genetic diversity and marker trait association for phytophthora resistance in chilli

Residual estimation of spirotetramat and its metabolites in chilli and soil by LC-MS/MS

Two applications of spirotetramat were done to study the dissipation and persistence of spirotetramat and its four different metabolites in chilli and soil at 10 days interval. Total spirotetramat residues were estimated by LC-MS/MS instrument. The mean initial deposits of total spirotetramat after application of spirotetramat 15.31 OD @ 60 (X dose), 75 (1.25 × dose) and 120 (2 × dose) g a.i. ha-1 on green chilli were found to vary from 0.38 to 0.83 mg kg-1 during the initial year. Spirotetramat and its metabolite residues in green chilli were found to be below limit of quantification (0.01 mg kg-1) after 15 days of application. The spirotetramat cis enol (the major metabolite) was formed in both the soil and the plant. The residues of spirotetramat-monohydroxy were below LOQ irrespective of any substrate during the estimation. In soil, the total initial spirotetramat deposits for the 1st year were found 0.09 for X dose, 0.12 for 1.25 × dose and 0.20 mg kg-1 for 2 × dose. After 3 days for both X and 1.25 × doses and 5 days for 2 × dose, the total spirotetramat residues were below LOQ. The spirotetramat's half-life values have been determined to be between 3.19 and 3.93 days and 1.00 and 1.59 days, respectively, in soil and green chilli fruits. One day waiting period is proposed for the safe consumption of green chilli when the spirotetramat was applied irrespective of the dose.

Population Genetic Analysis of Phytophthora colocasiae from Taro in Japan Using SSR Markers

Phytophthora colocasiae is an important pathogen that causes great economic losses in taro production in tropical and subtropical regions, especially in Japan. Understanding the genetic variations in P. colocasiae populations and their transmission patterns in Japan is essential for effective disease control. Here, the genetic diversity of 358 P. colocasiae isolates, including 348 from Japan, 7 from China, and 3 from Indonesia, was assessed using 11 simple sequence repeat (SSR) primer pairs with high polymorphism. The phylogenetic tree of the SSR locus showed that the isolates from Japan could be divided into 14 groups, with group A being the dominant group. Among foreign isolates, only six from mainland China were similar to those from Japan and clustered in groups B and E. Analysis of molecular variance (AMOVA), principal components analysis (PCA), and cluster analysis (K = 3) results revealed a moderate level of genetic diversity, mainly within individuals. Populations showed high heterozygosity, a lack of regional differentiation, and frequent gene flow. Analysis of mating types and ploidy levels revealed that A2 and self-fertile (SF) A2 types and tetraploids were dominant across populations. Explanations and hypotheses for the results can provide more effective strategies for disease management of taro leaf blight.

Association mapping for abiotic stress tolerance using heat- and drought-related syntenic markers in okra

BACKGROUND

Considerable production losses are caused by heat and drought stress in okra. Germplasm evaluation at genetic level is essential for the selection of promising genotypes. Lack of genomic information of okra limits the use of genetic markers. However, syntenic markers of some related family could be used for molecular characterization of major economic traits.

METHODS AND RESULTS

Herein, 56 okra genotypes were evaluated for drought and heat tolerance. Sixty-one expressed sequence tags (ESTs) identified for heat and drought tolerance in cotton were searched from literature surveys and databases. The identified ESTs were BLAST searched into okra unigene database. Primers of selected okra unigenes were synthesized and amplified in all genotypes using standard polymerase chain reaction (PCR) protocol. Marker trait association (MTA) of the syntenic unigenes were identified between genotypic and phenotypic data on the basis of linkage disequilibrium Functional syntenic analysis revealed that out of these 61 cotton ESTs 55 had functional homology with okra unigenes. These 55 unigenes were used as markers for further analysis (amplification). Okra genotypes showed significance variations for all the physo-morphological parameters under heat and drought stress. Genotypes Perbhani Karanti, IQRA-III, Selection Super Green, Anmol and Line Bourd performed better under drought stress whereas genotypes Perbhani Karanti, IQRA-III, Green Gold, OK-1501 and Selection Super Green showed heat tolerance. Fifty markers showed amplification in okra. Fifty-six okra genotypes were clustered into three distinct populations. LD analysis has shown most significant linkage between markers Unigene43786 and Unigene3662. MTAs using MLM and GLM models revealed that 23 markers have significant associations (p < 0.05) with different traits under control and stressed conditions. Relative water content is associated with four markers (Unigene10673, Unigene99547, Unigene152901, and Unigene129684) under drought conditions. Whereas, Electrolyte leakage was associated with 3 markers (Unigene109922, Unigene28667 and Unigene146907) under heat stress.

CONCLUSION

These identified unigenes may be helpful in the development of drought and heat tolerant genotypes in okra.