Meena Shekhar

Analyses of genetic diversity among maize inbred lines differing for resistance to pink borer and post-flowering stalk rot

Identification of the diverse sources of resistance is an important issue among the breeders for developing pest and disease free hybrids, to reduce the inoculum load, to prolong the life of inbred lines/hybrids and to reduce the cost of cultivation. Molecular diversity analysis was carried out among 23 maize inbred lines with respect to post flowering stalk rot and pink borer. Forty six SSR markers were employed among eight post flowering stalk rot (PFSR) and seven pink borer resistant lines along with eight other inbred lines to identify diverse resistant sources for developing resistant heterotic combinations to above pests and diseases. Number of alleles per SSR marker ranged from 2 to 9 averaging 4.11. The polymorphism information content (PIC) ranged from 0.272 to 0.839 with an average of 0.568. Discrimination rate (DR) of the markers ranged from 0.095 to 0.861 with a mean of 0.618. Number of alleles was highly correlated with PIC and DR. The pair-wise genetic dissimilarity values ranged from 0.05 to 0.84 with an overall mean of 0.64. Un-weighted neighbour joining clustering put 23 genotypes in two main clusters, which were further subdivided into 5 and 6 sub-clusters, respectively. We obtained 56 rare and 26 unique alleles in specific inbred lines, which can be used for identification of these lines. The present study has revealed considerable diversity among inbred lines differing for resistance against PFSR and pink borer; and provided ample scope for selection of parents for utilization in heterosis breeding

Potential biocontrol agents for the management of macrophomina phaseolina, incitant of charcoal rot in maize

Six isolates of Trichoderma harzianum were tested as potential bio-control agents under dual culture plate technique and inhibition through volatile substances for their efficacy against Macrophomina phaseolina, a charcoal rot pathogen of maize. Hyderabad isolate of T. harzianum inhibited 62.34% radial growth of M. phaseolina whereas isolates from Coimbatore, Dharwad, Delhi and Pantnagar inhibited 58%, 56%, 53%, and 51% of radial growth, respectively, over control. The effect of these biocontrol agents on production and size of sclerolia was also studied. Hyderabad isolate was found most effective by giving 69.48% reduction in sclerotia production and 57.36% reduction in sclerotial size over control as compared to other isolates. The effect of volatile metabolites of these bioagents on radial growth, sclerotia size and production of M. phaseolina were also studied and it was observed that again Hyderabad isolate was able to inhibit 41% on radial growth, 67.39% reduction on production and 45.46% reduction on size of the sclerotia of pathogen over the control which was the maximum compared all the other isolates. The results indicated that Hyderabad isolate of T. harzianum could be used as a potential biocontrol agent for minimizing PFSR incidence by reducing the primary inoculum in the soil by restricting the production of sclerotia compared to other isolates tested.

Sources of resistance to Exserohilum turcicum (Pass.) and Puccinia polysora (Underw.) incitant of Turcicum leaf blight and polysora rust of maize

A study was carried out to identify the sources of resistance to Turcicum leaf blight (TLB) and polysora rust in maize. Sixty indigenous and exotic inbred lines were evaluated under artificial epiphytotic conditions at two identified hot spot locations, Almora and Nagenahalli. After two years continuous screening, a total of 20 inbred lines were identified as a sources of resistance at both the locations for TLB, whereas 10 inbred lines were identified resistant against Polysora rust at Nagenahalli. A clear cut variation in virulence pattern in case of E. turcicum was observed. Some of the inbred inbred lines, i.e CM 138, CM 212, IML 235, NAI 135, showed resistant reaction in both the locations in the year 2005, whereas they acted as susceptible in 2006 at both locations. It was also observed that the Nagenahalli isolate of E. turcicum was more virulent than the Almora isolate.

Role of mould occurrence in aflatoxin build-up and variability of Aspergillus flavus isolates from maize grains across India

The present study was conducted to study the role of mould/fungal occurrence on aflatoxin build-up in maize grains and correlation between toxigenic and genetic variability present among isolates of Aspergillus flavus obtained from maize grain samples. Eighty-six maize samples were collected from farmers fields from various locations among the four maize growing agro-ecological zones of India. Among the microflora of maize grains studied, Aspergillus was the most predominant mould identified. Location Karnal (Haryana) was most sensitive to mould infection; 56.2% of samples), exhibited >20 μg/kg aflatoxin B1 (AFB1). On the other hand, Begusarai (Bihar) proves to be a less sensitive area for aflatoxin contamination with 90% of samples exhibiting <20 μg/kg AFB1. Varied isolates of A. flavus from grain samples were established in culture media and studied for toxigenic variability. In vitro high level variability (8,116.61-0.21 μg/kg) for aflatoxin production potential was found among these isolates. Random ...

Sources of resistance against post-flowering stalk rots of maize

The post-flowering stalk rots (PFSR) are a complex disease, which are widely distributed in almost all the maize growing regions across the globe. A number of fungi are involved in causing decay of the pith resulting in pre-mature wilting of the plants. Most of the commercially grown cultivars have shown a high level of disease incidence at the grain filling stage. A systematic breeding programme on PFSR was initiated in India in collaboration with Asian Regional Maize Program of CIMMYT. Under this programme, germplasm screening was carried out at four ‘hot spot’ locations in India for different diseases: Hyderabad (Cephalosporium maydis), Udaipur (Fusarium moniliforme), Ludhiana and Delhi (Macrophomina phaseolina). Across the locations, promising maize genotypes were artificially inoculated using the toothpick method, year after year; resistant plants were selfed to derive resistant inbreds. After extensive screening, three resistant lines, namely PFSR-13-5, JCY2-2-4-1-1-1-1 and JCY3-7-1-2-1-b-1, were identified. In addition, the resistance level of five pools/populations; (PFSR (Y)-C1, PFSR (white), Extra-early (White), P-100, P-300 and P-345) was upgraded to an acceptable level. These genotypes may prove useful for utilisation in breeding cultivars for resistance to PFSR.

Phytin: A Nutritional Inhibitor in Food and Feed - Review of Strategies and Challenges to Overcome the Menace in Maize

Maize (Zea mays L.) seeds forms an important ingredient of feed for poultry and swine and also a food for humans. In seeds stored phosphorus (P) largely occurs as phytin or Phytic acid (PA) a myo-inositol hexakisphosphate, Ins (1,2,3,4,5,6) P6, or InsP6. PA content is a major concern for nutritive value of maize. It is the storage compound of phosphorus in seeds accounting for up to 80% of the total seed phosphorus and contributing as much as 1.5% to the seed dry weight. The negatively charged phosphate in International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 7 Number 06 (2018) Journal homepage: http://www.ijcmas.com

Comparative study of qualitative and quantitative methods to determine toxicity level of Aspergillus flavus isolates in maize

An attempt was made to compare between easy and inexpensive qualitative method (ammonia vapour test) and analytical methods (thin layer chromatography and enzyme-linked immunosorbent assay) for identification of aflatoxigenic isolates of Aspergillus flavus in maize. In this comparative study the toxicity level of A. flavus isolates exhibited 100% agreement among ammonia vapour test, ELISA and TLC for highly toxigenic (>2000 ppb) and toxigenic (501–2000 ppb) isolates while 88.5% agreement observed for least toxic (<20 ppb) isolates. In ammonia vapour test 51% of A. flavus isolates showed creamish or no colour change corresponding to least toxic/atoxic (<20ppb) category estimated by ELISA. Similarly 22% highly toxic isolates exhibited plum red colour, 12% moderately toxic indicated pink colour and 10% toxic isolates showed red colour. However, 11.5% isolates were found to be false positive in cream colour category (least toxic) and 28.5% false negatives in pink colour (moderately toxic) category. The isolates from different agroclimatic zones of maize in India showed high variability for aflatoxin B1 (AFB1) production potential ranging from 0.214–8116.61 ppb. Toxigenic potential of Aspergillus flavus isolates in culture was further validated by inoculating maize grain sample with four different isolates with varied toxin producing ability. With good agreement percentage between cultural and analytical methods the study concludes the ammonia vapour test to be easy, inexpensive, reliable and time saving method that can be used for segregating or pre-screening of contaminated samples from bulk food/feed stock.

Genotypic variability in maize for aflatoxin contamination

A total of 60 maize genotype samples from different agroclimatic regions of India were collected. Fresh harvest of these maize samples comprising some commercial maize genotypes and some land races were kept under ambient storage conditions for 9 months duration at grain moisture ranges from 14% to 10.5% with a view to identifying the least contaminated maize genotype with aflatoxin. The purpose of this study was to identify the maize genotypes which can survive in ambient storage conditions with minimum spoilage. The response of various maize genotypes for AFB1 accumulation was variable in similar storage conditions. Promising genotypes which showed lower accumulation of AFB1 were identified: Shaktiman-1 (A QPM variety) by showing the lowest concentration of AFB1 (0.30 ppb) followed by KMH-1701 (0.40 ppb); HQPM-1 (0.50 ppb); and QPM-2-136 (0.60 ppb), whereas the most highly toxic sample was Mon - 4 (62.42 ppb) at grain moisture ranges from 12.6 to 11.1%. During the study it has been observed that Shaktiman-1 and other QPM genotypes showed minimum levels of AFB1. Further, it was confirmed by western blot analysis by comparing the resistant and susceptible genotype under artificially inoculated grains with Aspergillus flavus and uninoculated maize grains. It was observed that more chitinase activity was found in shaktiman-1, when the grains were artificially inoculated with A. flavus. The thickness of the seed coat and Aleuron layer was maximum in (90–100 μm) in Shaktiman compared to that of Pro-311 (80–85 μm). It was observed that the thickness of seed coat may act as a barrier for mold contamination and as a result the storage spoilage is minimised.

Potential bio-control agent for management of post-flowering stalk rot complex and maize plant health

The of aim of this study was to evaluate the potentiality of the native isolate of Trichoderma harzianum from IARI farm for the management of post-flowering stalk rot of maize and improvement of plant health. The treatment was tried as a seed treatment with the potent commercial formulation Kalisena SD (Aspergillus niger), neem kernel powder and effective fungicides (Thiram, Carbendazim, Captan) for comparison of its efficacy. The minimum disease was recorded in plots treated with native isolate both due to Fusarium moniliforme and Macrophomina phaseolina. The fungicides Carbendazim and Thiram ranked second in controlling the disease due to F. moniliforme and M. phaseolina, respectively. Plant health with respect to vigour and plant stand were found to be better than those of all the other treatments. It is concluded that the native isolate of T. harzianum may be used for maintaining good plant health and managing post-flowering stalk rot of maize.