Identification and isolation of genes responsible for increased shelf-life in guava (Psidium guajava L.)

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Date
2020
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Punjab Agricultural University, Ludhiana
Abstract
Guava is a climacteric fruit and ripening continuous even after harvesting leading to various textural changes. Abscisic acids (ABA) triggers the production of ripening hormone ethylene at fruit maturation stage. Most of the post-harvest changes are attributed to biosynthesis and signaling of ethylene further leading to cell wall metabolic changes imparting softness to fruit. Here, we tested 14 guava cultivars for ripening behavior and measured the physio-chemical attributes and biochemical changes at 3 ripening intervals in 2018-19 winter season crop. White fleshed Allahabad Safeda, Hisar Safeda, Punjab Safeda, Thailand guava, Shweta, Sardar guava and CISH-G5 and pink fleshed Punjab Pink, Lalit, Hisar Surkha, Purple local, 17-16, Punjab Kiran and Arka Kiran cultivars were analysed. Average TSS among genotypes varied from 8-11.5(ᵒbrix), Acidity 0.28 - 0.46%, reducing sugar 3.1-8.9%, Vitamin C 97.7 – 121 mg/100g, Firmness 4.66 - 6.73lb in 8 days of shelf life experiment. Highest fruit firmness at 4 days post-harvest was found in Thailand guava (9.8 lb). Our physico-chemical and gene expression analysis for ethylene & ABA biosynthesis, signaling and cell wall degrading enzyme genes reveal that ABA and ethylene biosynthesis is delayed in the highest shelf life cv. Thailand guava. Comparative genome sequence analysis of Thailand and Allahabad Safeda identified the specific nucleotide changes in ethylene biosynthesis gene SAM3 leading to change in glutamic acid to aspartic acid in an important domain. The genes ACO5, EIL3, EIN2, ERF6 and PL have SNPs in the untranslated and/or the promoter regions that might be impacting the docking of transcriptional machinery and concomitant delay in ripening. SNP based molecular markers in Thailand vs Allahabad Safeda might help in marker assisted selection for transferring superior alleles for delayed ripening in popular guava cultivars.
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