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Thirty-four 2-year-old ewes, of which 17 were native (Chokla) and 17 were Avivastra (Chokla 67.5%×32.5% Rambouillet) breeds of similar body weights, were selected. Both groups were maintained under the same management conditions with 8 hours daily grazing. In addition to grazing, each ewe received 300 g/day of a concentrate mixture comprising crude protein 20% and 70% total digestible nutrients. The ewes of both breeds were not mated during the study. The daily environmental parameters were recorded throughout the year, consisting of four main seasons, namely rainy, winter, spring and summer. Blood samples were collected into heparinized tubes during the morning hours for seasonal studies via indwelling jugular vein catheters to avoid stress to the animals, but for the diurnal studies the sampling was done twice daily at 07:00 and 17:00 continuously for three days in each season. Cortisol, thyroxine (T4) and triiodothyronine (T3) were estimated in the samples. The T4 and T3 profiles were maximal in the summer, followed by the rainy season in both groups, with no significant differences. However, the cortisol in both the groups was maximal during the spring rather than the summer. No significant differences were found in T3 concentration between morning and afternoon in any season in the native ewes but these animals showed significantly higher levels of T4 in the morning. The opposite was true for the crossbred animals with regard to both the T3 and T4 profiles. Significantly more cortisol was found in the evening than in the morning in both genetic groups in all seasons. 相似文献
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Leaf membrane stability (LMS) and the tetrazolium triphenyl chloride (TTC) test, heat susceptibility index (HSI), heat response index (HRI) and grain yield were used to evaluate 20 diverse wheat genotypes under normal and heat stress conditions for 2 years. The varieties ‘Seri’ and ‘Raj 3765’ had a desirable combination of cellular thermotolerance (TTC and LMS), heat tolerance (HRI) and high grain yield potential under heat stress, while ‘WH 730’ and ‘WH 533’ were better in cellular thermotolerance and heat tolerance. The varieties ‘PBW 373’ and ‘Kauz’ also performed better under heat stress in terms of grain yield and HSI/HRI. The varieties ‘Kanchan’, ‘PBW 373’, ‘NIAW 34’ and ‘GW 173’ were avoiders/escapers, ‘Seri’ and ‘HUW 234’ were tolerant to heat stress, while ‘WH 730’, ‘WH 533’, ‘Nesser’, ‘Raj 3765’ and ‘Kauz’ showed a combination of both. Correlation coefficients revealed that HRI was the most important trait, followed by TTC because the genotype having high HRI also had high grain yield and was better in mitochondrial viability and membrane stability under heat stress. Significance of GCA and SCA variances indicated the presence of both additive and dominant types of gene action. The use of the parents with high GCA effects, namely, ‘Raj 3765’ and ‘WH 730’ in a crossing programme for thermotolerance may provide desirable segregants through selection. 相似文献
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In an agrisilvicultural system having poplar (Populus deltoides, clone G-3) as a tree component and wheat crop as an intercrop, wheat yield was studied under five age classes of poplar and compared to wheat yield under pure cropping. A substantial reduction in wheat yield (23.3%) under three-year-old poplar plantation was observed. Maximum MAI (GBH, 20 cm) was recorded in a three-year-old poplar planting. Pruning after the third year permitted some recovery in yield. The reduction in wheat yield was significantly correlated with MAI (GBH) of poplar and occurred even under one-and-two-year-old poplar plantings. 相似文献
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Thirty diverse genotypes of bread wheat were evaluated for seed vigour index, germination percentage, root length, shoot length, root‐to‐shoot length ratio, coleoptile length and osmotic membrane stability under laboratory conditions. Considerable variation was observed for all the characters. Discrimination among the genotypes on the basis of mean values was better under normal than under moisture stress conditions, indicating suppression of variability under moisture stress conditions. Comparison of mean performance under normal and osmotic stress conditions indicated that the seed vigour index was the most sensitive trait, followed by shoot length, germination percentage and root length. The root‐to‐shoot length ratio, however, increased under osmotic stress. The magnitude of genetic components of variance and heritability were, in general, lower under osmotic stress than under normal conditions. All the characters except germination percentage, shoot length and coleoptile length showed considerable genetic variability. Heritability in the broad sense was also moderate to high for all the characters under both environments. Due to high heritability and genetic advance great benefit from selection can be expected for the osmotic membrane stability of leaf segments and root‐to‐shoot length ratio. Moderate progress can be expected from root length and seed vigour index. Correlation studies indicated that the osmotic membrane stability of the leaf segment was the most important trait, followed by root‐to‐shoot ratio and root length on the basis of their relationships with other traits. 相似文献
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Thirty-four non-pregnant 2-year-old ewes (17 Chokla (native) and 17 Avivastra (67.5% Chokla and 32.5% Rambouillet), of similar body weight, were maintained under the same management conditions with 8 hours daily grazing in an area with bushes, trees and miscellaneous other forage. The periods of active grazing, resting, resting while standing and lying, ruminating while standing or lying, walking time while grazing and bites per minute were recorded. The resting time differed significantly between the breeds, except in the winter. Both breeds spent more time standing during the summer and least during the spring. The crossbred animals spent more time lying in all the seasons except in the rainy season and almost the same pattern was observed for rumination time. A higher bite rate occurred in the crossbred ewes during the rainy and winter seasons, this being three times more than that for the native ewes. 相似文献
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Performance of wheat varieties under poplar (Populus deltoides Bartr.) plantations in Punjab (India)
Three varieties of wheat, viz., PBW-222, HD-2329 and PBW-34, were studied for grain yield potential under six-year-old poplar plantations. The order of yield reduction found was: PBW-34 (57.1%)>PBW-222 (19.4%)>HD-2329 (15.3%). The reduction in wheat yield was found to be significant under poplar plantations as compared to crops grown in open condition. Research needs to maintain the increased wheat production by evolving suitable ideotypes for an agrisilviculture system have been suggested. 相似文献