Molecular evidence to in vitro pollen bioassay for wilt resistance in chickpea
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Date
2007
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UAS, Dharwad
Abstract
Fusarium wilt caused by Fusarium oxysporum is the major biotic factor limiting
chickpea productivity in India. Despite the availability of stable resistance sources,
development of resistant varieties is hindered due to lack of effective screening techniques.
Conventional screening in sick plots is tedious and time consuming. Alternatively in vitro
pollen bioassay is emerging as an effective screening technique.
The pollen grains of sixteen diverse genotypes were tested for in vitro pollen tube
growth by adding different concentrations of fusaric acid to pollen germination medium. The
toxin inhibit pollen tube growth and genotypes showed significant variation for the
concentration of toxin to inhibit 50 per cent pollen tube growth.
The genotypes were phenotyped for wilt reaction using the in vivo seedling reaction to
fusaric acid. The genotypes were also tested for their wilt reaction using established
molecular markers. The genotypes which were categorized as wilt resistant using molecular
markers and in vivo seedling reaction were also resistant under in vitro pollen bioassay
requiring higher toxin concentration for pollen tube inhibition. Further, 50 recombinant
inbred lines of cross JG-62 (H1H1H2H2) x WR-315 (h1h1h2h2) were analyzed for their wilt
reaction using in vitro pollen bioassay. RILs showed significant variation for the toxin
concentration to inhibit pollen growth. The RILs were classified into resistant, susceptible
late wilters and susceptible early wilters using molecular markers. The resistant RILs
required significantly higher toxin concentration for pollen tube growth inhibition, followed
by late wilters and early wilters.
The efficiency of pollen bioassay in selecting resistant segregating was studied in F5
generation of BG-256 x WR-315. The resistant F5 progenies selected based on pollen
bioassay produced resistant F6 progenies.
The present study involving DNA markers linked to wilt resistance loci, three
different sets of genetic material and experiments performed over a period of time clearly
showed that the selection of genotypes for Fusarium wilt resistance based on pollen bioassay
is as reliable as marker assisted selection and/or sporophytic selection of not more.
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Keywords
Genetics and Plant Breeding