A rapid screening technique for drought resistance in potato (Solanum tuberosum L.)

Summary The reduction in growth in the dark of leaf dises floated over polyethylene glycol 6000 solution of water potential −0.4 MPa, relative to the growth of similar leaf dises floated over water for the same period, varied in the range 10–87% in 28 genotypes. The growth reductions in the genotypes tested were in general agreement with what is known about their drought resistance. Publication No. 906, Central Potato Research Institute, Simla.     

Growth and Distribution of Dry Matter in a Drought Tolerant and a Susceptible Potato Cultivar under Normal and Water Deficit Condition

The growth behaviour of Dekama (drought tolerant) and Kufri Jyoti (drought susceptible) was studied using potted plants maintained at well watered condition and water deficit condition respectively. Periodic harvestings were done starting from 50 days after planting till maturity. Recordings of plant height, leaf area, dry weights of different plant parts, the proportion of thinner and thicker roots, stomatal conductance and water saturation deficit were obtained. The plant height, leaf area and dry weight of shoot decreased to nearly the same extent in both the cultivars under stress. The stomatal conductance decreased by 61.7 % in Dekama and by 64 % in Kufri Jyoti due to water stress. Water saturation deficit increased by about 80 % in both the cultivars. The ratios of root to shoot and that of thinner to thicker root increased due to stress in both cultivars and this increase was 85 % and 71 % in Dekama and 64 % and 19 % in Kufri Jyoti respectively. The distribution of dry matter to leaf, stem, root were more at the expense of tuber under stress conditions in both cultivars. However, the tolerant cultivar Dekama got adjusted to the stress condition, with more dry matter partitioned to tubers in the last two samplings. The study points out the factors responsible for better drought tolerance of Dekama compared to Kufri Jyoti and the possible physiological traits useful for selecting drought tolerant cultivars.     

Effect of mulching on soil and plant water status, and the growth and yield of wheat (Triticum aestivum L.) in a semi-arid environment

Mulching is one of the important agronomic practices in conserving the soil moisture and modifying the soil physical environment. Wheat, the second most important cereal crop in India, is sensitive to soil moisture stress. Field experiments were conducted during winter seasons of 2004-2005 and 2005-2006 in a sandy loam soil to evaluate the soil and plant water status in wheat under synthetic (transparent and black polyethylene) and organic (rice husk) mulches with limited irrigation and compared with adequate irrigation with no mulch (conventional practices by the farmers). Though all the mulch treatments improved the soil moisture status, rice husk was found to be superior in maintaining optimum soil moisture condition for crop use. The residual soil moisture was also minimum, indicating effective utilization of moisture by the crop under RH. The plant water status, as evaluated by relative water content and leaf water potential were favourable under RH. Specific leaf weight, root length density and dry biomass were also greater in this treatment. Optimum soil and canopy thermal environment of wheat with limited fluctuations were observed under RH, even during dry periods. This produced comparable yield with less water use, enhancing the water use efficiency. Therefore, it may be concluded that under limited irrigation condition, RH mulching will be beneficial for wheat as it is able to maintain better soil and plant water status, leading to higher grain yield and enhanced water use efficiency.     

Use of sunlight to partially detoxify groundnut (peanut) cake flour and casein contaminated with aflatoxin B1

Sunlight destroyed 83 and 50% of the toxin added to casein and groundnut cake flour, respectively. Equilibrium dialysis revealed that both casein and groundnut protein bind aflatoxin but the toxin bound to casein appeared more photo-labile than that bound to groundnut protein.     

Measurement of cellular membrane thermostability to evaluate foliage heat tolerance of potato

Summary Cellular membrane thermostability of leaf tissue, measured by both leaching and direct conductivity, was used as an index for evaluating potato (Solanum tuberosum L.) leaf tolerance to high temperature. Experiments with eight genotypes showed that maximum differences between cultivars in response to temperature occurred at 52.5°C. The wide variability among the genotypes suggested that this index could be used to screen potato foliage for tolerance to heat. The results agreed well with visual scoring after exposing potted plants to 52.5°C. CPRI Publication No 854.     

Viability of excised embryos,shoot proliferation and in-vitro flowering in a species of rattan Calamus thwaitesii Becc.

Summary

92% of embryos excised from fresh mature unripe fruits of Calamus thwaitesii germinated in a modified Y3 medium with 0.05 mg l^±1 of 6-benzylaminopurine (BAP). This was higher than the 72% germination obtained with ripe seeds sown in soil. Stored seed lost viability within two weeks due to dehydration of embryos. Germination commenced with the differentiation of the haustorium and the cotyledonary sheath, observable in embryos germinating in vitro. This was followed by the development of the plumule. The first eophylls were simple and lanceloate. Decapitation of the in-vitro seedlings and transfer to a medium with higher levels of BAP at 5 or 8 mg l^±1 resulted in the production of multiple shoots after 4±5 months, initially from buds that developed around the collar region. Repeated subculture resulted in the development of a clustering habit similar to that of field clumps with a rhizome, axillary shoots and dormant buds. Two axillary meristems were induced to develop precociously into inflorescences. Incorporation of activated charcoal and alpha-naphthaleneacetic acid (NAA) with 5 or 8 mg l^±1 BAP reduced multiple shoot formation and brought about root development. Single shoots or clusters developed roots in a Y3 medium with reduced macro elements and supplemented with NAA (5.mg.l^±1) and activated charcoal. Nursery establishment with 65% survival of plantlets was possible. In-vitro culture of excised embryos could be recommended, as propagules could be made available whenever desired by rooting proliferated shoots. It also allowed the safe transport of germplasm.     

Effect of maleic hydrazide and 2,4,5-trichlorophenoxy propionic acid on ripening and quality of mango fruit

Dipping in hot water accelerated the ripening process and reduced fungal spoilage in Mangifera indica cv. Pairi mangoes. Accelerated ripening was counteracted by incorporation of maleic hydrazide (MH) in the dip water, thereby extending the storage life with minimum fungal spoilage. 2,4,5-Trichlorophenoxy propionic acid (2,4,5-TP) also delayed the ripening process, but did not improve skin colour. Hot water treatment with or without MH and 2,4,5-TP increased the carotene content of the flesh. These compounds did not significantly alter the chemical composition or quality of the fruit.     

Internodal elongation: A potential screening technique for heat tolerance in potato

Summary In pot culture experiments over 2 consecutive years, 20 potato genotypes of varying heat tolerance were grown under long day conditions and heat stressed by being exposed to high (38 °C/21 °C mean day/night) temperature. The percent increase in mean internode length of heat stressed plants over those grown at normal temperatue (25°C/16°C day/night) was correlated with the percent tuber dry matter yield of the heat stressed plants (r=0.618, P=0.01). In the same 20 genotypes, grown under short day conditions at normal temperature, the fraction of leaf bud cuttings exposed to high night temperature (23°C) that produced tuber initials correlated with the percentage increase in internode elongation in stem cuttings exposed to 25°C compared with those exposed to 15°C (r=0.680. P=0.01). Thus the relative changes in internode elongation are related to thermal tolerance, and it is suggested that this can be used as a selection criterion for heat tolerance.     

Regulation of ripening by chemicals in ‘Alphonso’ mango

Post-harvest dip treatment of ‘Alphonso’ mango with cycocel, alar, gibberellic acid and menadione bisulphite significantly retarded ripening, as judged by the number of ripe fruits, during storage at 28°C. However, after cycocel treatment, retardation of ripening was observed in the early part of storage only. The value for the Brix/acid ratio was low and that for firmness was high in fruits treated with gibberellic acid and menadione bisulphite, indicating their unripe character. The results suggest that mango ripening can be controlled by the use of chemicals.