Association mapping of heat stress related curding traits in Indian cauliflower
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Date
2020
Authors
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Journal ISSN
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Publisher
DIVISION OF VEGETABLE SCIENCE ICAR-INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI
Abstract
Cauliflower (Brassica oleracea var. botrytis L.) is a thermo-sensitive crop for the
development of its economic part ‘the curd’. Based on temperature requirement for curd
induction and development, there are four prevalent groups in cauliflower in India. The
genetic investigation so far showed its quantitative inheritance but the present
investigation was aimed to assess the association of curding traits with temperature
stress factor and assess genetic diversity and association using SSR markers and
genotyping by sequencing (GBS). To investigate this, the present study was undertaken
at two locations IARI, New Delhi and ICAR RC for NEH Region, Barapani using 91
genotypes as common for both locations during 2019-20. The trial was done in
complete randomized block design with three replications at each location, however,
the sowing time was delayed by two months at Barapani location to escape heavy
rainfall. Standard crop management practices were followed at both locations and eight
curd related traits were recorded from each genotype and analysed using statistical
softwares. For molecular diversity and GBS analysis, the genomic DNA was extracted
from 96 genotypes (including orange cauliflower, two of each broccoli and tropical
cabbage) and analysed using 90 SSR markers. Of them, clear 59 were polymorphic.
The observation on agro-morphological traits revealed high phenotypic coefficient of
variation and genotypic coefficient of variation (20%) for net curd weight (g),
marketable curd weight, and gross plant weight in both the location. High heritability
is observed for days to 50% curd initiation and days to 50% curd harvest, marketable
curd weight and net curd weight. Genotypic correlation coefficients indicate that most
of the traits showed positive and highly significant correlation.Under both environment
conditions it was found that Kt-25, Kt-22, BR-2 and Pusa Meghna for Delhi condition,
CC-14, DC-310-22, DC-135-199, Kt-20 and Kt-16 are the best suitable for Barapani
condition. Agro-morphological traits based clusters showed clear groups and matching
with traditional groups of maturity except few interchanges in early and mid-early
groups.
Molecular diversity analysis revealed significant diversity among the
cauliflower genotypes and the polymorphic information content (PIC) values was
116
highest for BoGMS0742 (0.68) followed by OI10D03 and BoGMS0162 (0.51) while
its mean value was 0.18. The STRUCTURE analysis could show four
subpopulationswith low to high admixture. The GBS analysis using the Illumina
sequencing platform for 96 genotypes for assessing diversity and association mapping
showed average of 3.146 million reads per plant sample. Total 35831 SNPs were
detected from all the nine chromosomes and the highest from chromosome 3. Twelve
QTL (five QTL for Delhi region and seven QTL for Meghalaya region) were identified
for various curding related traits on total of 6 different chromsomes. The genomic
information on curding traits in cauliflower particularly Indian type will facilitate
designing robust molecular for use in breeding varieties with adaptive plasticity for
temperature related curding traits to meet the long-time demand of growers.
Description
T-10353