Oxidative discolouration in whole-head and cut lettuce: biochemical and environmental influences on a complex phenotype and potential breeding strategies to improve shelf-life

Lettuce discolouration is a key post-harvest trait. The major enzyme controlling oxidative discolouration has long been considered to be polyphenol oxidase (PPO) however, levels of PPO and subsequent development of discolouration symptoms have not always correlated. The predominance of a latent state of the enzyme in plant tissues combined with substrate activation and contemporaneous suicide inactivation mechanisms are considered as potential explanations for this phenomenon. Leaf tissue physical properties have been associated with subsequent discolouration and these may be influenced by variation in nutrient availability, especially excess nitrogen and head maturity at harvest. Mild calcium and irrigation stress has also been associated with a reduction in subsequent discolouration, although excess irrigation has been linked to increased discolouration potentially through leaf physical properties. These environmental factors, including high temperature and UV light intensities, often have impacts on levels of phenolic compounds linking the environmental responses to the biochemistry of the PPO pathway. Breeding strategies targeting the PALand PPOpathway biochemistry and environmental response genes are discussed as a more cost-effective method of mitigating oxidative discolouration then either modified atmosphere packaging or post-harvest treatments, although current understanding of the biochemistry means that such programs are likely to be limited in nature and it is likely that they will need to be deployed alongside other methods for the foreseeable future

Improvement of baby corn yield by using green manure

Suitable rates of compost and chemical fertilizers to improve baby corn yield have been reported ; information on an appropriate type of green manure to increase its yield is rather limited. Use of green manure showed from a farmer with a practicable method in actual fields, which is not expensive and can be adjusted to the physical and chemical characteristics of soil. Therefore , the major objective of this experiment was to find a way to improve the yield of baby corn through the use of five types of green manure treatments and control, comprising no green manure (control), mung bean (Vigna radiata L.), hyacinth bean (Lablab purpureus L.), sword bean (Canavaria ensiformis L.), copwea (Vigna unguiculata L.) and sesbania (Sesbania rostrata Brem.). The treatments were arranged in a randomized complete block design with four replications on June 2000, tested at the experimental field of Agricultural Technology Department, Technology Faculty, Mahasarakham University, Kantharawichai District, Maha Sarakham Province. The results indicated that sesbania used as green manure resulted in a fresh weight content higher than the others, and promoted plant height, plant diameter, leaf area, ear number / plant, yield both before and after peeling / rai, ear weight both before and after peeling / ear, ear diameter after peeling and standard yield content / rai consequently. In addition, the ear color after peeling was satisfactory for consumers. Yield contents / rai grown on the other sources of green manures were significantly lower (P < 0.01