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Carotenoids are important micronutrients required by humans for growth and development. Yellow maize among cereals possesses sufficient carotenoids, and thus, it is important to genetically dissect such traits for proper utilization in breeding programme. Twenty-one maize hybrids generated using novel inbreds with rare allele of β-carotene hydroxylase (crtRB1) that enhances kernel β-carotene, were evaluated at two diverse maize growing locations. Lutein, zeaxanthin and β-cryptoxanthin were positively correlated, while β-carotene showed negative correlation with other carotenoids. Grain yield did not show association with carotenoids. Preponderance of additive gene action was observed for lutein, zeaxanthin, β-cryptoxanthin and β-carotene. Experimental hybrids were much superior for kernel β-carotene compared to commercial hybrids. Based on SCA effects, high yielding experimental hybrids were identified for provitamin A and non-provitamin A carotenoids. These novel hybrid combinations of maize possessing rare allele of crtRB1 hold promise in maize biofortification programme to alleviate vitamin A deficiency and degenerative diseases in humans.
One thousand four hundred and eighty three spring wheat germplasm (Triticum aestivum L.) lines comprising Indian as well as exotic lines were screened for resistance to spot blotch disease during winter 2014-15 at hot spot locations i.e., Banaras Hindu University, Varanasi and Uttar Banga Krishi Vishwavidyalaya, Cooch Behar. Severity of the disease at different stages beginning from tillering to dough stage was recorded. Location Severity Index (LSI) of Varanasi was higher than Cooch Behar. Twenty eight accessions were resistant or highly resistant at both locations. These 28 accessions were validated during the winter season (2015–2016). These germplasm were also evaluated at four environments for agronomic traits. Out of 28 accessions, seven (IC564121, IC529684, IC443669, IC443652, IC529962, IC548325 and EC178071-331) were highly resistant across the locations and over the years of study. These accessions comprised one exotic and six indigenous accessions belonging to Uttarakhand and Haryana. Two lines (IC529962 and IC443652) had higher yield than the best check at all the locations. These lines showing highly resistant reaction alongwith wider adaptability can be expedited for direct cultivation or for the development of high yielding and disease resistant cultivars. These lines can also be used for identification of novel resistance gene using allele mining tools and their deployment for the development of spot blotch resistant cultivars.
Carotenoids play vital role in growth and development of human beings. Yellow maize kernel contains carotenoids that possess provitamin A and antioxidant activity. Multilocation based analyses of 105 maize inbreds of indigenous and exotic origin revealed wide genetic variation for lutein (0.2–11.3 μg/g), zeaxanthin (0.2–20.0 μg/g) and β-carotene (0.0–15.0 μg/g). For β-cryptoxanthin, low variation (0.1–3.3 μg/g) was observed. Carotenoids were quite stable over environments that played minor role in causing variation. The heritability (>90%) and genetic advance (>75%) were high for all the carotenoid components. Zeaxanthin showed positive correlation with lutein and β-cryptoxanthin, while β-carotene, the major provitamin A carotenoid, did not show correlation with other carotenoids. Kernel colour was positively correlated with lutein (0.25), zeaxanthin (0.47) and β-cryptoxanthin (0.44), but not with β-carotene (0.04). This suggested that visual selection based on kernel colour will be misleading in selecting provitamin A-rich genotypes. Inbreds with provitamin A and non-provitamin A carotenoids identified in the present study will help in development of biofortified maize hybrids.
Physiological breeding complementing the conventional approach is increasingly being explored in wheat in view of stagnating annual genetic yield gain. Designing improved plant types required knowledge about physiological traits associated with yield gain in the past. Fourteen wheat varieties including 12 historically important and popular (mega) wheat cultivars and two recently registered varieties were observed for various physiological traits for two years. Both breeding period and genotypes within breeding period accounted for significant differences for most of the physiological traits. Regression analysis indicated curvilinear trend for leaf area index (LAI), flag leaf area, and root length and root weight. Near perfect leaf area index (LAI 5.94) with semi-erect leaves and higher flag leaf area was observed in all time mega variety HD 2967 indicated the importance of plant architecture and crop canopy in yield maximization. Linear declining trend was observed for coleoptile length, number of stomata per cm2 and flag leaf length. Increasing trend for total chlorophyll content and normalized difference for vegetative indices (NDVI) at both vegetative and flowering stage indicated the importance of leaf greenness in yield improvement. Root length has continuously declined except for the latest released varieties, however no such trend was observed for root weight. We propose that grain yield stabilization at still higher level can be achieved by increasing photosynthetic capacity, optimizing the crop canopy slightly less than the optimum, and better partitioning to grain yield through directed physiological based breeding.
