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  • Author or Editor: R. Behl x
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Drought and high temperature are especially considered as key stress factors with high potential impact on crop yield. The aim of this study was to investigate the effect of short periods of high temperature, drought and their combination at different growth stages of plant under controlled conditions. The effects of high temperature and drought on grain yield were additive. However, high temperature increased the degree of water stress and the combined effects of drought and high temperature were much more severe than those of each individual treatment. High temperature and drought applied at post- anthesis shortened duration of maturation, grain filling duration and reduced grain yield, mean grain weight, grain number and thousand-grain weight.

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The regeneration potential of pearl millet, a crop which is of vital importance for farmers in semi-arid tropical regions, was evaluated in a 12 × 12 line × tester cross involving six male sterile (A) lines from five systems of cytoplasmic-genic male sterility, namely two male sterile lines from system A1 (MS81A1, MS8A1), and one each from A2 (Pb313A2), A3 (Pb402A3), A4 (MS81A4) and A5 (MS81A5), the six corresponding maintainer (B) lines 81B1, 8B1, Pb313B2, Pb402B3, 81B4and 81B5, and twelve restorer (R) lines, namely H90/4-5, H77/833-2, G73-107, CSSC46-2, 77/245, 78/711, 77/273, ICR 161, ISK48, 77/28-2, 77/180 and Raj 42. The 24 parents and 144 crosses were grown separately in contiguous blocks in a randomized block design with two replications in three treatments each in 2000 and 2001 at the Research Farm, Bajra Section, Department of Plant Breeding, CCS HAU, Hisar. The plot size was 2.5 m × 0.45 m with 10 cm intra-row spacing. The genotypes (A lines, B lines, R lines, A × R crosses, B × R crosses), sowing dates, years, year × sowing date and genotype × treatment interactions (direct and reciprocal) exhibited significant differences. The comparison of mean performance of the early-sown non-ratooned crop vs. ratooned (cut, regenerated) vs. late-sown unratooned crop treatments revealed that both the grain and dry fodder yields and the major yield-contributing characters exhibited little reduction in the ratoon crop, while the total tillers at maturity and the effective tillers increased in the ratoon crop in comparison to the direct-sown crop. Additional green fodder yields of 189.63 g and 144.02 g per plant, harvested 40 days after sowing (DAS) in the ratoon crops in 2000 and 2001, respectively, and similar grain and dry fodder yields emphasized the utility of cutting and regeneration in pearl millet. The ratooning ability of genotypes, assessed from the ratio of the performance of various characters in ratoon and early and late sown unratooned crops for yield and major yield components was high for a number of lines, testers and hybrids. Most of the hybrids involved one or two parents with good regeneration potential. Sufficient genetic variability was observed for regeneration and ratooning ability, which was found to be under genetic control, suggesting that regeneration potential could be incorporated in genotypes with high yield. A base population developed from promising parents and crosses can be improved by cyclic breeding.

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A field experiment was carried out to investigate the establishment of phosphate-dissolving strains of Azotobacter chroococcum, including soil isolates (wild type) and their mutants, in the rhizosphere and their effect on the growth attributes and root biomass of three genetically divergent wheat cultivars (Triticum aestivum L.). Four fertilizer doses were applied: 90 kg N ha—1, 90 kg N + 60 kg P2O5ha—1, 120 kg N ha—1and 120 kg N + 60 kg P2O5ha—1, besides a control plot without fertilizers or bioinoculants. Phosphate-solubilizing and phytohormone-producing parent soil isolates and mutant strains of A. chroococcum were isolated and selected following the enrichment method. On an overall basis the mutant strains performed better than the soil isolates for in vitro phosphate solubilization (11–14%) and growth hormone production (11.35%). Seed inoculation of wheat varieties with phosphate-solubilizing and phytohormone-producing A. chroococcum showed a better response over the control. Mutant strains of A. chroococcum showed a higher increase in grain (15.30%) and straw (15.10%) yield over the control and better survival (12–14%) in the rhizosphere as compared to their parent soil isolate (P4). Mutant strain M15 performed better in all three varieties in terms of increase in grain yield (20.8%) and root biomass (20.6%) over the control.

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ADP-glucose pyrophosphorylase (AGPase) activity in the developing grains of two contrasting wheat cultivars WH730 (thermo-tolerant) and UP2565 (thermo-sensitive) was determined in relation to their allosteric effectors and grain growth. The developing grains (35 days after anthesis) were excised from the middle portion of spikes of wheat genotypes subjected to high temperature, drought and their combination at booting, post-anthesis and booting+post-anthesis. The impact of stress treatments was studied by measuring starch content and yield attributes in relation to AGPase activity. AGPase, a key enzyme for starch synthesis, is allosterically activated by 3-phosphoglyceric acid (3-PGA) and inhibited by inorganic phosphate (Pi). Sensitivity of AGPase towards individual and combined high temperature and drought has not been adequately investigated, therefore the present study analyzed AGPase activity, its sensitivity to allosteric effectors under influence of high temperature, drought in order to elucidate the relationship of AGPase with starch accumulation and grain growth. Significant difference in behavior of the enzyme and its allosteric effectors were observed between the two cultivars under high temperature and/or drought. AGPase activity was substantially decreased by high temperature, drought and was found to be positively correlated with the 3-PGA, starch accumulation and yield attributes, while negatively correlated with Pi content. The results showed that effects of high temperature and drought were additive and more severe at booting+post-anthesis stage. Such studies might help in understanding the control mechanisms associated with the pathway of starch biosynthesis and thus provide chemical means to manipulate starch content vis-à-vis grain yield under heat and drought stress.

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The present investigation was conducted to investigate the impact of bio-inoculants on the magnitude and direction of gene effects and mean performance for root length density, root biomass per plant, AMF colonization in roots and micronutrient uptake (Cu, Fe, Mn, Zn) in wheat under low input field conditions. The material for study comprised three wheat cultivars, WH 147 (low mineral input), WH 533 (drought-tolerant), Raj 3077 (high mineral input) and six generations (P 1 , P 2 , F 1 , F 2 , BC 1 and BC 2 ) of three crosses, namely WH 147 × WH 533, WH 533 × Raj 3077 and WH 147 × Raj 3077. The experiment was conducted in a randomized block design with three replications having three treatments, i.e. (i) control; (ii) inoculation with arbuscular mycorrhizal fungi (AMF, Glomus fasciculatum ); (iii) dual inoculation with AMF and Azotobacter chroococcum ( Azc ). The fertilizer doses in all three treatments were 80 kg N + 40 kg P + 18 kg ZnSO 4 ha −1 . Root length density, root biomass per plant, AMF colonization in roots and Zn and Mn content were found to be maximum after dual inoculation with AMF+ Azc in all three crosses. Joint scaling tests revealed that additive-dominance gene effects were mainly operative in governing the expression of root biomass, Cu and Zn content in all three crosses for all three treatments (i.e. control, AMF and AMF + Azc ). Pedigree selection in crosses WH 147 × WH 533 and WH 147 × Raj 3077 could be effective for breeding pure lines of wheat for sustainable agriculture (low input genotypes responsive to biofertilizers such as AMF and Azotobacter ).

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The present investigation was conducted to study the impact of bio-inoculants under low input field conditions on the magnitude and direction of gene effects and the mean performance of nitrogen (N) and phosphorus (P) use in wheat. Three wheat cultivars suitable for different agro-ecological conditions, i.e. WH 147 (low mineral input), WH 533 (water deficit), Raj 3077 (high mineral input), and six generations (P 1 , P 2 , F 1 , F 2 , BC 1 and BC 2 ) of three crosses, namely WH 147 × WH 533, WH 533 × Raj 3077 and WH 147 × Raj 3077, were evaluated in a randomized block design with three replications under low input field conditions (80 kg N + 40 kg P + 18 kg ZnSO 4 doses applied in each treatment) with three treatments, i.e. control, inoculation with arbuscular mycorrhiza fungi (AMF, Glomus fasciculatum ) and dual inoculation with AMF and Azotobacter chroococcum ( Azc ). Bioinoculation with AMF and AMF+ Azc had a positive impact on the mean performance of all the wheat crosses. The mean performance of AMF was maximum in the cross WH 147 × WH 533 for N and P response (%), N and P use index (%) and P content (ppm), whereas for N and P uptake it was maximum in the cross WH 147 × Raj 3077. The response and use index for N and P were better in the combined AMF+ Azc treatment in all three crosses. The adequacy of the additive-dominance model for the phosphorus uptake (mg/plant) by all three crosses in all three treatments (i.e. control, AMF, AMF+ Azc ) suggested that additive (d) and dominance (h) gene effects mainly governed the inheritance of this trait. In all cases, digenic interactions were present, where the duplicate type of epistasis prevailed except for the P content in the control in the cross WH 147 × WH 533, where the complementary type of interaction was present. Pedigree selection in crosses WH 147 × WH 533 and WH 147 × Raj 3077 could be effective for breeding pure lines of wheat for sustainable agriculture (low input genotypes responsive to biofertilizers such as AMF and Azotobacter ).

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An experiment was conducted for the measurement of membrane thermostability and chlorophyll fluorescence in parents and their six F 1 ’s at post-anthesis stage. Parents and F 1 ’s showed significant variation for high temperature stress tolerance in late sown conditions. Genotype PBW 435 and the cross PBW 343 × PBW 435 exhibited less relative injury and greater thermotolerance possibly through maintaining cellular membrane integrity under high temperature stress. Data based on chlorophyll fluorescence revealed reduction of mean values of all genotypes and their F 1 ’s for F v /F m , proportion of efficiently working Photo system II (PSII) units among the total PS II population in late sown conditions. The genotypes EIGN 8, UP 2425 and Raj 3765 and F 1 s EIGN 8 × UP 2425 and PBW 343 × WH 283 figured important for further wheat improvement programmes.

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Inheritance of male sterility and fertility restoration of the A 1 system of cytoplasmic-nuclear male sterility in pearl millet was investigated using 12 crosses among three diverse male sterile lines (A-lines) and four diverse restorers (R-lines). Individual plants from R- lines were used to make crosses on A-lines. The segregation pattern of male sterile (S) and male fertile (F) plants observed in F 2 and BC 1 in two seasons at ICRISAT, Patancheru was suggestive more likely of a single-gene control of male sterility and fertility restoration. However, a 3-gene model of male sterility/fertility restoration where dominant alleles at any two of the three duplicate complimentary loci will lead to male fertility could not be ruled out, nor could be ruled out a 2-gene control with duplicate interaction. There was indication of variability even within a highly inbred R-line for fertility restoration gene(s). Depending on the genetic constitution of the R-lines at these loci, even the 3-gene model can lead to single-gene segregation ratios as observed in most of the F 2s and backcrosses, and 2-gene ratios as observed in a few F 2s and backcrosses. The deviations from these expected ratios in some of the crosses influenced by modifiers and environmental conditions generally resulted from the excess of fertile plants in the rainy season or excess of sterile plants in the dry season, the more so in crosses involving an A-line which has been reported to be relatively more unstable for male sterility.

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The impact of high temperature stress, normally encountered during grain development phases in wheat under late sown conditions, was studied by measuring grain growth rate (mg day−1 grain−1), grain yield (g plant−1) in relation to ADP glucose pyrophosphorylase (AGPase) activity (nmol mg−1 min−1), a key regulatory enzyme in starch biosynthesis. The experimental material comprised nine genetically diverse homozygous genotypes of spring wheat and their six F1s. These were grown in randomised block design with three replications at CCS Haryana Agricultural University, Hisar, India on two dates of sowing 26th November, 2007 (timely, E1) and 24th December, 2007 (late, E2). The rate of grain growth was greatly reduced as temperature increased in late sown environment. Grain growth rate among the parental genotypes was highest in UP 2425 and cross PBW 343 × PBW 435 in both the environments. Mean ADP glucose pyrophosphorylase (AGPase) activity was maximum at 14 days after anthesis in timely sown while in late sown the activity was maximum at 21 days after anthesis in PBW 435, EIGN 1 and EIGN 8 and crosses EIGN 8 × UP 2425, EIGN 1 × Raj 3765 and PBW 343 × PBW 435. A significant positive association in both timely and late sown environments was evident between grain yield and grain growth rate, while in late sown environment, strong positive and significant correlation was observed between grain yield and grain growth rate and also between grain growth rate and AGPase activity in crosses PBW 343 ×WH 283, PBW 343 × WH 542 and PBW 343 × PBW 435. This suggested that increase in grain growth rate and AGPase activities resulted in increase in grain yield and have considerable impact on the yield performance of wheat.

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Field experiments were conducted over two years under low input conditions to know the influence of bio-inoculants, namely arbuscular mycorrhiza fungi (AMF, Glomus fasciculatum ) and Azotobacter chroococcum (Azc) on the performance and gene effects for important root and plant characters in three crosses of wheat (WH147×WH157, WH147×PBW175 and WH147×WH542). Six generations representing P 1 , P 2 , F 1 , F 2 , BC 1 and BC 2 populations of each cross were grown in randomized block design with three replications. The estimate of means (m) indicated that bio-inoculants enhanced the mean performance of most of the characters and root length density and grain yield in some crosses only. Crop season also showed considerable effect on impact of bio-inoculants. The joint scaling test revealed adequacy of additive-dominance model of gene effects for root biomass, root length density, flag leaf area, tillers/plant, grain weight and grain yield in all the crosses and bio-inoculants treatments in both years. The AMF treatment brought about changes in the magnitude and significance of additive component for root biomass, plant height, flag leaf area in all the three crosses. Both additive (d) and dominance (h) components were affected with respect to grain yield in WH147×WH157 and WH147×WH542. The dominant component was important for tillers/plant, grain yield, root length in control, as well as bio-inoculants treated populations of WH147×PBW175 but treatment of AMF and AMF+ Azc reduced the magnitude of h and increased the magnitude of d. Digenic interactions were prominent for grains/spike in WH147×WH157. Magnitude of digenic interactions was higher under bio-inoculation. Simple pedigree and bulk pedigree methods are suggested to capitalize on adequate additive gene effects for developing bio-inoculants responsive wheat genotypes.

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