Abstract Vegetables are usually herbaceous and succulent plants. This succulent nature of vegetable crops makes them susceptible to attack by a wide variety of pests. Traditionally insect resistance has not been as widely investigated as disease resistance due to relatively smaller economic losses caused by insects as compared to pathogens in earlier times. But owing to indiscriminate use of pesticides, population of natural enemies has declined which in turn has increased the frequency of insect epidemics. Outbreak of Tuta absoluta in tomato is a recent example. Intense selection of crops has reduced the genetic variability and has increased their genetic vulnerability to insects. Some pests like Meloidogyne spp., Helicoverpa and aphids are polyphagous and cannot be managed by chemical sprays. In such cases resorting to insect resistance is the best option for a breeder. But development of insect resistant variety takes considerable time and efforts. Recent advancements in omics approaches has accelerated the resistance breeding. Genetic markers permit effective indirect selection for insect resistant plants. They are effective tools for identifying genomic regions controlling pest resistance. Molecular markers permit transfer of precise DNA segments from disease resistant species to susceptible cultivars thus preventing the problem of linkage drag. This review highlights the achievements in recent years in vegetable resistance breeding via various omics-based approaches viz . genomics, transcriptomics, proteomics and metabolomics.
SUMMARY A simple yet effective field screening technique for estimating drought tolerance is described. It involves growing plants in sloping plots which are opposite each other and connected to sub-channels lined with polyethylene sheet. The slopes are designed to achieve instant surface run-off and the sub-channels connected to a main channel for rapid drainage of rain-water. Stress is created at different stages of crop growth by manipulating the timing of irrigation and covering the soil surface with polyethylene sheeting. The technique proved effective even in the monsoon season which is characterized by irregular intensity and distribution of rainfall. Data on six characters for 80 genotypes of pearl millet grown in six artificially created environments representing different levels of moisture stress are discussed. The ‘slope’ technique was effective in creating different levels of moisture stress at various stages of crop growth and in distinguishing categories of genotypes by their relative drought tolerance.
The impact of arbuscular mycorrhizal fungi (AMF), inorganic phosphorus (P), and irrigation regimes was studied in an okra (Abelmoschus esculentus)–pea (Pisum sativum) cropping system in an acidic Alfisol. Experimentation was carried out at Palampur, India, in a randomized bock design (RBD), replicated three times with fourteen treatments comprising AM fungi (Glomus mosseae), inorganic phosphorus (50, 75, and 100% soil-test-based recommended P dose), irrigation regimes (at 40 and 80% available water capacity), generalized recommended NPK and irrigations (GRD), and farmers' practice. Effects of AM fungi on plant height, leaf area index (LAI), and dry-matter accumulation (DMA) were nominal at early crop growth stage, i.e., 50 DAS (days after sowing). However, at 100 DAS, AMF imbedded treatments led to higher plant height (4%), LAI (3%), and DMA (6%) in okra, whereas in pea the magnitude of increase in these parameters following AMF inoculation was 6, 5, and 8%, respectively, over non-AMF counterparts. AMF + 75% soil-test-based P dose at either of these irrigation regimes gave statistically similar yields in both okra and pea as that obtained under 100% soil-test-based P dose at either of two irrigation regimes, thus indicating an economy of about 25% in soil-test-based P dose. Regarding nutrient harvest index in okra and pea, statistically similar values were registered with most nutrients under both AMF inoculated and non-AMF counterparts. In the case of okra, P harvest index was registered less by 3% with AMF inoculation; however, its magnitude increased by 3% in pea following AMF inoculation compared to non-AMF counterparts at similar levels of P and irrigation. At completion of two cycles of okra-pea system, AMF imbedded treatments did not alter available soil nutrient status significantly in comparison to non-AMF counterparts. Overall, current study suggests that practice of AMF inoculation has great potential in enhancing growth parameters for better productivity, fertilizer-P economy, and nutrient harvest efficiency in okra-pea production system in Himalayan acidic Alfisol.
The genotype-environment interaction was studied for six females, sixteen pollinator parents and their 96 F, hybrids alongwith three checks for grain yield under three environments. Both predictable (linear) and unpredictable (non-linear) portions of gxe interactions were found to be significant for heterozygous (hybrids) and homozygous (parents) populations. The magnitude of predictable portion was relatively higher among parents whereas in hybrids' it was almost equal. Stability id general appeared to be a property of the individual genotype as even for significant unpredictable gxe interaction, prediction could be made in respect of many genotypes. There was lack of association between bi and S2 di and xi and S2di both in homozygous and heterozygous populations which indicated that independent genetic systems controlled these parameters.
100 genotypes comprising of 73 inbreds, 21 hybrids, 3 experimental varieties, 1 male sterile lines and 2 maintiners grown during the summer, 1978 at ICRISAT, Hyderabad were tested for germination on May 9, 1978 after 17 days of storage...
An experiment was conducted during the rainy season of 1988 and 1989 and the dry season of 1989 and 1990 to study the effect of yield potential, drought escape and tolerance on the grain yield of pearl millet [Pennisetum glaucum (L.) R. Br. emend. Stuntz] under stress. Different types of drought and heat stress occurred, viz moderate and severe post-flowering drought and sevcrepre-flowecing drought, combined with either high or low temperature during grain filling. Yield potential was only related to yield under stress when pre-flowering drought was combined with low temperatures. Escape was the predominant factor if temperature was high, except if combined with pre-flowering drought, in which case tolerance became more important. These results show that for stressed environments, selection for yield potential is of limited use. The importance of escape and tolerance, however, depends on the timing and intensity of stress occurrence. If pearl millet-growing regions can be charaoterized based on occurrence of abiotic stress, breeders can select more efficiently for plant traits that enhance stress adaptation in specific target environments.
Genetic analysis was conducted for a 15-parent diailel cross, (F1s, excluding reciprocals) of pearl millet, grown in 3 different environments. The yield components studied were head weight, head length and head number per plant. For all the characters, both additive and non-additive kinds of genetic variances were present with a predominance for the latter. However, in the presence of high g x e interactions, the estimates of gene number differentiating the parents were underestimated and also, the heritabilities were underestimated. Based on the gca effects of the parents and the sca effects of the hybrids emanating from high gca parents, It has heen shown that the material presented good potentialities for line selection which might be valuable in developing hybrids as well as for developing synthetics/composites
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