Genetic studies of high temperature tolerance in early sown Indian mustard [Brassica juncea (L.) Czern & Coss.]
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Date
2017
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Dr. Rajendra Prasad Central Agricultural University, Pusa (Samastipur)
Abstract
The present investigation entitled “Genetic studies of high temperature tolerance in early sown Indian mustard [Brassica juncea (L.) Czern & Coss.]” was carried out with 35 Indian mustard genotypes including two checks (Pusa Mahak and Pusa Mustard-25) from AICRP-RM centres located around India. These genotypes, under laboratory condition, were evaluated for seven physiological characters under three temperature stresses (25, 30 & 35oC) at germination for selection of three thermotolerant sources to be used as testers (Line x Tester Design). Same 35 genotypes, under field trial, were evaluated in RCBD with three replications at Research Farm of TCA, Dholi, Muzaffarpur, Bihar for 21 morpho-physiological-quality attributes (including 4 traits at two phenological stages; pre-flowering (30 DAS), and post flowering (60 DAS) for variability and diversity studies under early sown (06.10.2014) conditions at 32.20C temperature during Rabi 2014-15. Three thermo tolerant testers crossed with seven lines to get 21 crosses and these 31 genotypes (21 crosses i.e F1s + 7 lines + 3 testers) were evaluated in RCBD with three replications for same set of traits during Rabi 2015-16 for line x tester analysis under early sown (05.10.2015 at 35.10C temperature) conditions for combining ability and heterosis studies.
Best thermo-tolerant genotypes reflecting superiority in physiological traits at germination upto 35oC in Lab. Experiment were RAURD-78 (EL, RL, SL, SDW and VI); NDRE-7 (EL, RL, RSR and VI) and TPM-1 (EL, RL & RSR). High GCV, PCV, heritability in broad sense coupled with high genetic advance under selection at 25, 30 & 35 0C was reflected by RSR, SDW and EL whereas, in field experiment by LAI & SDW (30 & 60 DAS), CGR, SB/pl and HI thus indicating preponderance of additive gene action which could be effectively utilized by Brassica breeders.
NRC-DR-2, RAURD-78 and Pusa Mahak (Oligogenotypic clusters) alongwith
TPM-1 and NDRE-7, based on physiological traits at germination; whereas DRMR-150-35, TPM-1 (Oligogenotypic clusters) along with Rajendra Sufalam, RAURD-78, KMR-10-2 and Pusa
Mahak (morpho-physio-quality traits field evaluation trial) were promising divergent genotypes, reflected overall usefulness of Pusa Mahak, RAURD-78 and TPM-1 with superior per se performance for EL, HI , DPM-Early and DME (TPM-1; VI, SDW at 30 DAS, RL and LAI ( RAURD-78 and EL, SDW at 30 DAS and OC (NDRE-7) further validated their performance as thermotolerant parents utilized in hybridization. High yielding, divergent genotypes with superiority in many component traits were DRMR-150-35, Rajendra Sufalm, PM-28, NDRE-4 and Pusa Mahak, out of which DRMR-150-35, Rajendra Sufalam and Pusa Mahak were most suitable from divergence studies further proved their genetic worth. SDW, EL and RSR (25, 30, 35oC) at germination stage and HI followed by SS, DPM & LPMA (field trial) reflected maximum contribution towards total divergence. There was no parallelism between genetic diversity and their geographical distribution and sizeable number of morpho-physiological-quality traits at different phenological stages (germination, pre-flowering at 30 DAS & post flowering 60 DAS) highly influenced the group constellation of 35 Indian mustard genotypes. The cross between genotypes of cluster II x VI, IV x V, V x VI and III x IV (lab. evaluation) whereas, V x VII, VI x VII (Field Evaluation) were expectedly more divergent based on their inter-cluster distance. Interestingly crosses attempted in L x T design, namely RH-30/TPM-1 (cross no. 4), Varuna/TPM-1 (cross no. 16) and PM-25/TPM-1 (cross no. 19) were also among divergent combinations (both Lab & Field D2 set basis) further validated their importance.
Positive, significant association coupled with high positive direct effect of DPM, HI & SB/pl revealed the importance of these traits while selecting for high temperature tolerance under early sown Indian mustard. Most reliable and yield predictor characters were SB/pl and HI as they also reflected high heritability coupled with high genetic advance under selection.
The best general combiners, on the basis of GCA and per se performance were NRC-DR-2 (SLW at 30 DAS, CC at 60 DAS and LAI at 30 DAS), RH-30 (SLW at 60 DAS and PB/pl), Rajendra Sufalam (SLW at 60 DAS and 1000 SW), NDRE-7 (Early DFFO & DPM), TPM-1 (SS) and RAURD-78 (PB/Pl). The crosses based on SCA, standard heterosis (SH) and per se performance, namely RH-30/RAURD-78, Rajendra Sufalam/NDRE-7, PM-25/RAURD-78 and RH-8814/TPM-1 were ranked as top yielders. The crosses RH-30/RAURD-78, involving both good (HxH) general combiners might be useful in heterosis breeding. The crosses involving HxL or LxH general combiners, namely Rajendra Sufalm/NDRE-7, and PM-25/RAURD-78 may throw desirable segregants and effectively utilized in transgressive breeding programme.
Thus, the present study reflects the usefulness of RAURD-78, NDRE-7 and TPM-1 as good source of thermotolerance for early sown mustard as well as divergent genotypes and good general combiners for 1000 SW, Early DFFO & DPM and SS (both high GCA and per se basis) respectively. Four best economic crosses for SY/pl were RH-30/RAURD-78, Rajendra Sufalam/NDRE-7, PM-25/RAURD-78 and RH-8814/TPM-1 also reflected superior economic heterosis for SLW (60 DAS), CGR, PH (60 DAS) tall, PB/Pl & SB/Pl in all these crosses alongwith individually superior economic heterosis for PH (30 DAS), DFFO (late), DPM (late), DME & SOMS (RH-30/RAURD-78), 1000 SW & OC (Rajendra Sufalam/NDRE-7); DPM late (PM-25/RAURD-78 and RH-8814/TPM-1). These superior economic heterotic F1s significantly out yielding in yield alongwtih above mentioned morpho-physiological and quality attributes may subsequently be utilized in future breeding endeavours. Amongst all the morpho-physio-quality characters (lab. & field trails) harvest index proven its merit as most important character which contributed maximum towards total divergence, significant positive association and high positive direct effect toward yield alongwith high h2 (bs) and high GAM was most important determinant and yield predictor for the thermo-tolerant mustard genetic enhancement under early sown conditions.
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