Indian 1. Plant Physiol., Vol XXXVll, No.3 pp. 142-146 (September, 1994)
PHYSIOLOGICAL BASIS OF YIELD AND ITS COMPONENTS IN RAPESEED
MUSTARD WITH REFERENCE TO PHOTOPERIOD
s.c.BHARGAVA" AND S.N. BHARDWAJ Division of Plant Physiology
Indian Agricultural Research Institute. New Delhi-l 10012 Received on 12 Nov., 1992
Brassicabiomass as well as yield are influenced by the duration of photoperiod. Long
photoperiod (LD) enhanced productivity in B. carlnata (cv. BS-2B-84) whereas in B. campestris (cv. Pusa Kalyani) and B. juncea (cv. Varuna) it is favoured by natural day (ND). Short photoperiod (SD) decreased biomass and seed yield Seed yieldin general was found linearly related with biomass. days taken to flowering and number of pods on
primary'and secondary branches. Any change brought about in these parameters by photoperiods affects the productivity.
. Rapeseed-mustard crop is the second most important source of edible oil after groundnut and considerable effOrts are being made by breeders for improving its prodUction and stability in different Indian agro-climatic regions. Yield differences in different species of genus Brassica have generally been attributed to variations in parameters like leaf area index, net assimilation rate and total dry matter production (Mehrotraelai, 1976; Bhargava and Tomar, 1982; Chauhan and Bhargava, 1984) which are significantly influenced both by plant density as well as nitrogen feltilization (Khader and Bhargava, 1985). However, information available on production physiol ogy with respect to, photoperiod is rather lacking. The present study was, therefore, undeltaken to explain varia tion in yield of Brassica spp. as influenced by photope riOd.Thishas a relevance in predicting the crop behaviour under varying agro-climatic conditions.
MATERIALS AND METHODS
Four Brassicacultivars B. campestris(pusa Kalyani), B.juncea(ValUna), B. napwdBO-IS), B. carinala(BS 2B-84) were sown at IARI, New Delhi for two consecu tive seasons on 19th Oct., 1985, 25th Oct., 1986. The
* Corresponding author.
photoperiod of short day (SO, 8 hr), long day (LD, 24 hr i.e. natural light supplimented with low intensity incan descent lamps) and natural day (ND, 9-10 hrunder Delhi conditions) was given to all the fourcultivars. N.P.K. was supplied as basal dose at the rate of40:40:40 kglha, seeds were handsown and thinned to 15 cm apart in 45 cm row to row distance to give the plant population of 15 plants! m2
. Three irrigations were given at 35, 60 and 90 days
after sowing in addition to one for germinating the seeds. The crop was sprayed with 5% malathion to control aphid attack. The experimental design was split plot with three replication. Photopeliod was taken as main treatment and cultivars as sub-plot treatment.
At maturity of each cultivar, plants grown in one square metre land surface were harvested for yield and yield components. Siliques and stems were separated and air dried. Dried siliques were thrashed and seeds were cleaned. Different order branches, pods and seeds per pod were counted and their weights recorded. The ratio ofseed weight to the tOLal dry matter (harvest index) at maturity were calculated.
RESULTS AND DISCUSSION
Table I :Effect of daylength on yield and its components in four
Brassicaspecies (Mean of two seasons and three replications)
PHOTOPElUOD EFFECT IN RAPESEED-MUSTARD
Cultivar Day Seed yield Biomass III (%) No. of pods Seeds/pod 1000 seed Total Days to
length (g/m'Z) (g/m 2) perm2 (No.) weight (g) braneh No.' flowering
Pusa Kalyani SD
ND LD 221.82 348.10 339.80 1002.7 1045.6 1014.2 22.03 33.30 32.78 6422.90 7727.07 6665.78 10.5 13.9 13.3 3.80 3.30 3.90 763.35 730.00 636.65 53.15 48.10 49.10
ND LD 219.60 304.40 302.90 726.7 930.2 922.6 28.80 31.60 32.14 6086.34 6304.25 5898.30 9.3 11.7 10.5 4.42 4.70 5.31 698.30 740.05 714.75 56.95 50.65 45.65
ND LD 184.50 363.90 460.60 858.8 1232.4 1545.3 21.45 28.10 29.08 5190.41 6827.80 7430.13 11.3 16.1 18.6 3.20 3.10 3.36 265.00 356.65 416.70 89.35 77.40 77.52
ND LD 249.70 415.30 312.90 1567.7 1936.7 1524.7 16.12 21.40 19.79 9265.66 10110.73 7884.12 10.3 14.3 11.9 2.83 2.90 3.32 2663.30 3104.80 1823.30 112.10 108.20 100..70
SEm± 10.45 16.38 0.54 95.75 0.51 0.51 23.13 5.76
CD (5%) 30.67 48.03 1.58 280.84 1.49 1.51 67.84 16.89
seed yield and biomass were produced under ND and the • minimum under SD. The differences in yield and biomass due to day length treatment in these two cultivars ap peared mainly due to numher of pods and seeds per pod. In Varona lowest harvest index of 28.8% under SO was accompanied with low seed yield and biomass. This seemed due to lowest I
aOO-seedweight and minimum number of total branches under this day length. In BO-15 maximum seed yield and its components were produced under LO and minimum under SO except IOOO-seed weight which wa<; minimum under ND. Like Pusa Kal yani and Varona, BS-2B-84 also showed maximum seed yield and biomass under ND and minimum under SO. So was the case with its harvest index. The differences in these parameters appeared due to number of seed per pod. The maximum seed yield and biomass under NO was ruso accompanied with maximum number of pods and total branches. Likewise the minimum seed yield and hiomass under SD was accompanied with minimum I aaO-seed weight. Total number of branches, biomass and numher of pods were produced maximally in
Brassicacultivar BS-2B-84. The minimum oftotal hranch number and pod number were produced by BO-15 and minimum biomass by Varona.
Pod number on different order hranches are given in Table-II. In Pusa Kalyani and Varuna the maximum pods were produced on primary branches followed by second
ary, main and tertiary irrespective of day length. BO-15 and BS-2B-84 followed different trend. In BO-15 maxi mum pods were produced on primary followed hy main and secondary branches. Tertiary branches in this cuItivar were almost negligible and hence the pod number. In BS 2B-84 highest number of pods were borne on secondary branches, whi Ie main axis had minimum number of pods. Pods on primary branches were more than telliary in this cultivar. Maximum pods were produced in primary branches in all the cultivar except BS-2B-84. BO-I5 produced the lowest number of pods and BS-2B-84 the highest.
"NEELAM KUMARI et a1
Table II :Effect ofday length on poddistribution pattern (No.lm2) on different order branches in four
Brassicaspecies (mean oftwo seasons and three replications)
Cultivar Number of pods per m2 on different order branches
length Main Primary Secondary Tertiary Total
Pusa Kalyani SD ND LD 642.25 804.17 714.82 3482.51 4211.50 3695.32 2207.32 2567.25 2079.82 90.85 144.15 175.82 6442.93 7727.07 6665.78 Varuna SD ND LD 646.50 777.92 691.44 3255.67 3223.07 3100.72 2020.82 2170.70 2050.32 163.35 132.57 55.82 6086.34 6304.25 5898.30 BO-15 SD ND LD 1158.92 1277.27 1261.32 3639.82 4641.42 4862.14 391.67 909.17
5190.41 6827.80 7430.13 8S-2B-84 SD ND LD 219.82 275.82 264.12 2844.92 2845.82 2256.63 4982.10 5016.62 4298.30 1218.82 1972.47 1065.07 9265.66 10110.73 7884.12
SEm± 12.96 155.25 113.39 228.30 79.66
CD at 5% P 38.00 455.35 332.59 669.63 233.65
m :Effect of day length on pod weight (g/m2) on different order branches in four
Brassicaspecies at harvest (Mean of two seasons and three replications)
Cultivar Pod weight (g/m2) on different order branches
length Main Primary Secondary Tertiary Total
Pusa Kalyani SD ND LD 54.77 111.89 97.64 287.90 417.30 390.25 116.85 152.13 168.68 2.5 10.98 459.52 683.82 667.55
ND LD 53.30 88.15 80.93 175.21 324.62 310.74 117.32 111.02 141.38 3.48 2.92 3.60 349.31 526.71 536.62
ND LD 106.5 180.52 177.81 315.33 514.47 630.55 40.06 60.65
461.89 755.64 985.23
ND LD 18.73 35.40 32.03 170.39 289.16 202.75 281.60 436.30 372.17 34.37 111.27 43.96 504.60 872.13 650.91
~Em:t 1.77 11.53 10.68 2.18 26.81
145 PHOTOPERIOD EFFECT IN RAPESEED-MUSTARD
cultivars BO-15 had the highest pod weight followed by BS-2B-84, Pusa Kalyani and Varuna.
The present findings suggest that seed yield of Bras sica spp. is related linearly with biomass produced and days taken to 50% flowering. Thus late maturing types BO-15 (B. napus) and BS-2B-84 (B. cannata) had higher seed yield. On the other hand harvest index as well as flowering duration were not related to seed yield, whereas harvest index possessed a negative relationship with biomass. Similar results have also been reported by Taro and Morgan (1975), Mehrotra
etaI, (1976) and Chauhan and Bhargava (1984).
Since seed yield depends plimarily on number of pods produced, number of seeds per pod and 1000-seed weight (Campbell and Kondra, 1978, Ahmed, 1979), these parameters were analysed. BS-2B-84 (B.cminata) produced the maximum number of pods, whereas BO-15 (B. napus) had the highest number of seeds per pod and Varuna the maximum 1000-seed weight.
Seed yield in general varied with pods produced. In order to estimate the contribution of pods located on different order branches to seed yield, coefficients of correlation and regression equation were computed by pooling the two seasons data offour cultivars raised under three day length and presented in Table IV. It is seen that seed yield was correlated positively with number of pods located on plimary (r=0.72) and secondary (r=0.43)
Table IV : Coefficients of inter-correlation (r value) between number of pods located at different order branches and seed yield in Brassica species (Number of character= 72).
Correlation Number of pods located on branch position between
Main axis Primary Secondary Tertiary
Seed yield 0.239 0.715 0.429 0.213
Pods on main axis 0.645 -0.626 -0.612
Pods on primary
branches 0.044 -0.256
Pods on secondary
Significant at 1% P=O.302 and "r 5% P=0.232
branches. Further, pod number on main axis was associ ated positively with pod number on primary branches (r=0.65) but negatively with pods on secondary (r=0.63) and teltiary (1'=0.061) branches. Pods number on primary branches also had negative relationship with pods on te11iary branches (r=0.26), whereas, pod number on sec ondary and tertiary branches possessed positive correla tion (r=0.80) with each other.
Polynomial relations between pod number on differ ent order branches, an independent variable and seed yield dependent variable were Significant (multiple r=0.83). The quadric regression equations for predicting seed yield is
Y=-lS.683 +0.046*M+0.062*P+ 0.021*s+ 0.044*T (± 0.069) (± O.01S) (±O.01S) (± 0.027)
where Y =seed yield and M, P, Sand T are the number of pods located on main axis (stem), primary, secondary and tertiary branches respecti vely. Values given inparen thesis are the standard error of estimate.
It, thus, appears that seed yield in Brassica cUltivars is built up mainly due to the production of pods on primary branches (T-value: 4.19 significant). ProdUction of more pods on main axis seems undesirable as it would reduce the number of pods produced on secondary and tertiary branches. This is in agreement with suggestions made by Bhargava
etaI (1983) that main stem should bear not more than 40 siliques for Bra5sica ecotypes.
Short day treatment decreased seed yield in all the cultivars; BO-IS suffered the most followed by BS-2B 84. The decrease was found related to corresponding decrease in biomass production and harvest indices. In our earlier experiment differences in biomass production due to photoperiod has been shown to be related with leaf area index and/or net assimilation rate (Neelam, 1989). Present study thus shows that seed yield differences with the cultivar and photoperiod is traced to corresponding differences in leaf area index and or net assimilation rate. Previous studies also support this view (Mehrotra
146 NEELAM KUMARI et aI.
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