K. M. Manjaiah

Stability Performance of Inductively Coupled Plasma Mass Spectrometry-Phenotyped Kernel Minerals Concentration and Grain Yield in Maize in Different Agro-Climatic Zones.

Deficiency of iron and zinc causes micronutrient malnutrition or hidden hunger, which severely affects ~25% of global population. Genetic biofortification of maize has emerged as cost effective and sustainable approach in addressing malnourishment of iron and zinc deficiency. Therefore, understanding the genetic variation and stability of kernel micronutrients and grain yield of the maize inbreds is a prerequisite in breeding micronutrient-rich high yielding hybrids to alleviate micronutrient malnutrition. We report here, the genetic variability and stability of the kernel micronutrients concentration and grain yield in a set of 50 maize inbred panel selected from the national and the international centres that were raised at six different maize growing regions of India. Phenotyping of kernels using inductively coupled plasma mass spectrometry (ICP-MS) revealed considerable variability for kernel minerals concentration (iron: 18.88 to 47.65 mg kg–1; zinc: 5.41 to 30.85 mg kg–1; manganese: 3.30 to17.73 mg kg–1; copper: 0.53 to 5.48 mg kg–1) and grain yield (826.6 to 5413 kg ha–1). Significant positive correlation was observed between kernel iron and zinc within (r = 0.37 to r = 0.52, p < 0.05) and across locations (r = 0.44, p < 0.01). Variance components of the additive main effects and multiplicative interactions (AMMI) model showed significant genotype and genotype × environment interaction for kernel minerals concentration and grain yield. Most of the variation was contributed by genotype main effect for kernel iron (39.6%), manganese (41.34%) and copper (41.12%), and environment main effects for both kernel zinc (40.5%) and grain yield (37.0%). Genotype main effect plus genotype-by-environment interaction (GGE) biplot identified several mega environments for kernel minerals and grain yield. Comparison of stability parameters revealed AMMI stability value (ASV) as the better representative of the AMMI stability parameters. Dynamic stability parameter GGE distance (GGED) showed strong and positive correlation with both mean kernel concentrations and grain yield. Inbreds (CM-501, SKV-775, HUZM-185) identified from the present investigation will be useful in developing micronutrient-rich as well as stable maize hybrids without compromising grain yield.

Effect of citric acid treatment on release of phosphorus, aluminium and iron from three dissimilar soils of India

To evaluate different mathematical models for describing cumulative release of phosphorus (P), aluminium (Al) and iron (Fe) by citric acid (CA) from soil, an experiment was conducted in packed soil columns with three contrasting soils viz. Alfisol, Vertisol and Inceptisol. The soils were saturated with CA at 0, 5, 10, 20, 40 and 100 mg L−1, the leachate were collected by liquid displacement at 15, 30, 45, 60 day intervals, and P, Al and Fe releases were analyzed. The release data were fitted to linear, quadratic, exponential, logarithmic, and power form of equations. The results revealed that the highest cumulative release of P, Al and Fe was observed in the 40 mg L−1 CA treatment. In the majority of cases, the relationship between CA concentration and cumulative release of ions fitted well in quadratic equation (y = ax2 + bx + c). The Fe and Al releases with time were fitted well in power-form (y = atb), while the cumulative P release in linear equation (y = mx + c). The study also revealed that a substantial amount of released P could serve as potential source of plant nutrient in fixation prone soils. The study demonstrated that CA can be used as a ‘solubilizer’ of soil P, 40 mg L−1 dose released the highest P, 0–20 mg L−1 dose was observed to be economical and 5 mg L−1 was the most promising dose in Alfisol.

Thermal stability of organic carbon in soil aggregates of maize-wheat system in semi arid India

Abstract Understanding the stability and carbon retention ability of aggregates under common cropping sequences is essential to ascertain terrestrial carbon storage. Surface soil samples (0-15 cm) were collected and dry sieved to separate the macro (>250µm) and micro sized aggregates (<250µm). The separated aggregates were subjected to 60 days incubation at four different temperatures (25, 30, 35 and 40 °C). Nutrient management was more prominent than tillage in determining water stable aggregates. 100% organic treated plots in bed planting and mineral fertilizers + crop residues in conventional tillage gave maximum mean weight diameter values of 1.01 and 0.95 respectively. Irrespective of the treatments, microaggregates were found to be poorer in carbon content, but richer in their capacity to retain it by way of larger activation energies. The Q 10 values were found to be higher in microaggregates than macroaggregates for all treatments, confirming the thermal sensitivity hypothesis of stable carbon fractions.

Genetic variability and correlation of kernel micronutrients among exotic quality protein maize inbreds and their utility in breeding programme

Micronutrient malnutrition is a widespread problem known to affect millions of children and women. However, the adverse effects of micronutrient deficiency can be overcome through self-targeting, cost-effective and sustainable genetic biofortification approach, which is mainly based on staple food crops. Since maize has emerged as a prominent future crop especially for India, developing maize hybrids that are rich in kernel micronutrients will help in reducing the problems of micronutrient malnutrition. Here, we report variability of kernel Fe and Zn in 120 exotic Quality Protein Maize (QPM) inbreds and kernel Mn and Cu in a representative subset of 68 lines. A wide range of genetic variation was found among genotypes for all the kernel micronutrients: Fe (16.6–83.4 ppm), Zn (16.4–53.2 ppm), Mn (1.7–34.8 ppm) and Cu (0.5–9.5 ppm). Higher mean for kernel Fe and Zn in QPM inbreds suggests possible influence of opaque2 gene and/or modifiers present in them. Significant and positive correlation was observed among kernel Fe, Zn, Mn and Cu. Genetic diversity based on all four micronutrients grouped 68 lines into three major clusters with a mean coefficient of genetic dissimilarity of 2.46. Parental combinations were selected from different heterotic pools and maturity groups to develop high-yielding hybrids enriched with micronutrients.

Fractions, uptake and fixation capacity of phosphorus and potassium in three contrasting soil orders

A controlled greenhouse experiment was conducted to study the fraction, uptake and fixation of phosphorus (P) and potassium (K) in three soils with contrasting characteristics. The experiment was carried out in two phases, viz., sorghum-Sudangrass depletion and test crop experiment with maize with three levels of fertility status (depleted, original and fertilized with 40 mg kg -1 P and K) and two levels of rhizospheric status (rhizosphere and non rhizosphere). Clay was separated by ultrasonic vibration followed by fractionation into colloidal and non colloidal clay and short-range order (SRO) minerals, P and K fixation were measured in these clays. Phosphorus and potassium fractions and uptake were measured in soil samples. The results showed that, available and non-exchangeable potassium was highest in Vertisol and Inceptisol, respectively. Calcium-P was the dominant fraction in soil and highest in Inceptisol. Maximum K-fixation capacity for both the clay fractions was found in Vertisol (32.57% for colloidal clay and 37.94% for non colloidal clay), depleted soils (30.58% for colloidal clay and 31.04% for non colloidal clay) and rhizosphere (28.34% for colloidal clay and 29.59% for non colloidal clay). Phosphorus fixation was highest in Alfisol (58.72% for colloidal clay and 67.26% for non colloidal clay), depleted fertility status (53.41% for colloidal clay 55.45% for non colloidal clay) and non-rhizosphere (52.53% for colloidal clay and 54.26% for non colloidal clay) for both the clays. Phosphorus fixation was positively correlated with different pools of iron and aluminum compounds whereas, potassium fixation showed positive significant correlation with amorphous ferri-alumino silicate content.

Marker-assisted introgression of opaque2 allele for rapid conversion of elite hybrids into quality protein maize

Maize is a valuable source of food and feed worldwide. Maize endosperm protein is, however nutritionally poor due to the reduced levels of two essential amino acids, lysine and tryptophan. In this study, recessive opaque2 (o2) allele that confers enhanced endosperm lysine and tryptophan, was introgressed using marker-assisted backcross breeding into three normal inbred lines (HKI323, HKI1105 and HKI1128). These are the parental lines of three popular medium-maturing single cross hybrids (HM4, HM8 and HM9) in India. Gene-based simple sequence repeat (SSR) markers (umc1066 and phi057) were successfully deployed for introgression of o2 allele. Background selection using genome-based SSRs helped in recovering

Microsatellite marker-based genetic diversity among quality protein maize (QPM) inbreds differing for kernel iron and zinc

>96%

Transformation of short-range order minerals in maize(Zea mays L.) rhizosphere

>96% of recurrent parent genome. The newly developed quality protein maize (QPM) inbreds showed modified kernels (25–50% opaqueness) coupled with high degree of phenotypic resemblance to the respective recipient lines, including grain yield. In addition, endosperm protein quality showed increased lysine and tryptophan in the inbreds to the range of 52–95% and 47–118%, respectively. The reconstituted QPM hybrids recorded significant enhancement of endosperm lysine (48–74%) and tryptophan (55–100%) in the endosperm. The QPM hybrids exhibited high phenotypic similarity with the original hybrids for morphological and yield contributing traits along with responses to some major diseases like turcicum leaf blight and maydis leaf blight. The grain yield of QPM hybrids was at par with their original versions under multilocation testing. These elite, high-yielding QPM hybrids with improved protein quality have been released and notified for commercial cultivation, and hold significant promise for improving nutritional security.