Conductivity Testing of Seeds

Chemical divergence of the Juglans Regia L. across districts Swat and Dir, Khyber Pakhtunkhwa, Pakistan

Juglans regia L. are nutritious fruit bearing plants mostly found in Northern areas of Pakistan. The population of walnuts was explored from district Dir and Swat Khyber Pakhtunkhwa, Pakistan for their geographical, climatic and chemical divergence. The geographical differences such as altitude, latitude and longitude whereas climatic differences viz. soil EC, soil pH, precipitations, intensity of light, temperature and soil temperature. In both districts TPC ranged from 211.2±0.6 to 227.8±0.4 mg/100g, RSA ranged from 43.32±1.5% to 52.18±0.4%, conductivity ranged from 296.43±0.6 to 312.22±0.3 S/m and elemental composition such as iron, copper, calcium, zinc and magnesium in Dir differs from 0.312±0.032, 0.209±0.13, 20.0±0.313, 0.406±0.10 and 10.2±0.030 mg/L to 0.543±0.65, 0.698±0.82, 28.7±0.234, 0.685±0.15 and 17.6±0.015 mg/L respectively. Altitude and temperature showed a correlation with total phenolics contents and radical scavenging activity while soil pH, precipitations, soil temperature, soil Ec and light intensity indicated a weak correlation with chemical traits of walnuts. Further studies of walnuts are needed to explore their therapeutically important phytochemicals to succeed naturally pharmaceutical nutrients of the maximum significance for the health of human beings.

Characterization of green seed, an enhancer of abi3-1 in Arabidopsis that affects seed longevity

Seeds are usually stored in physiological conditions in which they gradually lose their viability and vigor depending on storage conditions, storage time, and genotype. Very little is known about the underlying genetics of seed storability and seed deterioration. We analyzed a mutant in Arabidopsis disturbed in seed storability. This mutant was isolated as a grs (green-seeded) mutant in an abi3-1 (abscisic acid 3) mutant background. Genetic and physiological characterization showed that the monogenic grs mutant was not visibly green seeded and mapped on chromosome 4. This enhancer mutation did not affect the ABA sensitivity of seed germination or seed dormancy but was found to affect seed storability and seedling vigor. Seed storability was assessed in a controlled deterioration test, in which the germination capacity of the mutant decreased with the duration of the treatment. The decrease in viability and vigor was confirmed by storing the seeds in two relative humidities (RHs) for a prolonged period. At 60% RH, the mutant lost germinability, but storage at 32% RH showed no decrease of germination although seed vigor decreased. The decrease in viability and vigor could be related to an increase in conductivity, suggesting membrane deterioration. This was not affected by light conditions during imbibition, expected to influence the generation of active oxygen species. During seed maturation, ABI3 regulates several processes: acquiring dormancy and long-term storability and loss of chlorophyll. Our results indicate that GRS is a common regulator in the latter two but not of dormancy/germination.

Zoospore homing and infection events: effects of the biocontrol bacterium Burkholderia cepacia AMMDR1 on two oomycete pathogens of pea (Pisum sativum L.)

Burkholderia cepacia AMMDR1 is a biocontrol agent that protects pea and sweet corn seeds from Pythium damping-off in field experiments. The goal of this work was to understand the effect of B. cepacia AMMDR1 on Pythium aphanidermatum and Aphanomyces euteiches zoospore homing events and on infection of pea seeds or roots. In vitro, B. cepacia AMMDR1 caused zoospore lysis, prevented cyst germination, and inhibited germ tube growth of both oomycetes. B. cepacia AMMDR1 also reduced the attractiveness of seed exudates to Pythium zoospores to nondetectable levels. However, when present at high levels on seeds, B. cepacia AMMDR1 had little net effect on zoospore attraction, probably because it also enhanced seed exudation. Seed-applied B. cepacia AMMDR1 dramatically reduced the incidence of infection by Pythium zoospores in situ compared with an antibiosis-deficient Tn5 mutant strain. This mutant strain also decreased Pythium infection incidence to some extent, but only when the pathogen inoculum potential was low. B. cepacia AMMDR1 did not affect attraction of Aphanomyces zoospores or Aphanomyces root rot incidence. These results suggest that B. cepacia AMMDR1 controls P. aphanidermatum largely through antibiosis, but competition for zoospore-attracting compounds can contribute to the effect. Differences in suppression of Aphanomyces and Pythium are discussed in relation to differences in the ecology of the two pathogens.