Vishal Nath

Assimilate Partitioning Behavior in Relation to Fruit Growth in ‘Shahi’ Litchi

Investigations were undertaken to develop a better understanding of assimilate partitioning behavior in litchi, with respect to the role of stored assimilates translocated from other sources in the plant during the fruiting season. The first experiment examined the fruit growth pattern in the litchi ‘Shahi’. The second experiment focused on the limitation of assimilate supply to litchi fruits by leaf removal and girdling. The third experiment was aimed at fulfilling the assimilate requirement of growing litchi bunches through current photosynthesis by foliar application of a photosynthesis enhancer (triacontanol). The fruits exhibited a sigmoidal growth pattern with a phase of rapid growth 40 to 60 days after fruit set. Irrespective of method or distance of source limitation, the maximum percent of fruit drop was observed when the source limitation treatments were imposed 30 days after fruit set. Source limitation at all the distances resulted in significant increases in percent of fruit drop over those with no source limitations. With respect to different treatments, all forms of source limitation resulted in significant increase in fruit drop over the control. The results suggest that a contribution of carbohydrate from current photosynthesis for partial fulfillment of total carbon demand of growing fruits is necessary. Only no limitation of current photosynthesis contributed towards 0% loss in fruit weight while a limitation of carbohydrate translocation (girdling) contributed towards an 8.5% loss in fruit weight. However, under the condition of limited carbohydrate translocation, restriction on current photosynthesis caused a 19.1% loss in average fruit weight. Studies on foliar application of photosynthesis enhancers (triacontanol) on fruit drop in litchi under restricted (girdled) and unrestricted translocation of assimilate from other parts of the plant were conducted. These indicated a reduction in the rate of fruit drop with an increase in the concentration of triacontanol in case of unrestricted translocation of assimilate. However, under restricted assimilate translocation, increasing concentrations of triacontanol did not result in reducing the percent of fruit drop. Hence, the study clearly indicated the major role of translocated assimilates from other plant parts in fulfilling the assimilate demand of growing fruits in litchi where current photosynthesis contributes partially towards assimilate demand.

Impact of Climate Change on Tropical Fruit Production Systems and its Mitigation Strategies

Scientists are almost of unanimous opinion that tropics will be the first and most to suffer due to climate change even though the magnitude of projected change as well as past climate trend is moderate as compared to other part of the world. Reasons are though complex, include poor economic conditions of majority of population, higher dependence on natural resources and ecosystem service and relatively narrow temperature ranges. Projection of climate change for tropics indicates rise in temperature of 0.4–1 °C, 0.8–3.2 °C and 1.2–6 °C by the 2020, 2050 and 2100 respectively as compared to base line period (1961–1990). Atmospheric CO2 concentration is likely to reach 550–800 ppm from the present level of 400 ppm by the end of this century. The change associated with climate has never been smooth and likely to be expressed in terms of increased uncertainties and extremities of weather. Number of heat waves witnessed during last 25 years (1990–2015) in tropics has exceeded as compared to preceding 70 years. Similarly the number of extreme rainfall events as well as drought has also increased in recent past. These changes are likely to impact natural resources, societies and their interdependence.

Training and Pruning for Improved Postharvest Fruit Quality

The postharvest fruit quality depends on the maintenance and health of the fruit trees in orchard. The various preharvest operations, such as irrigation, training, pruning, fertilizer application, spray of various plant growth regulators, insecticides, and pesticides are the deciding factors that regulate the ultimate quality of the fruits during postharvest handling and storage. Training is done to achieve the desirable shape and form of the trees while pruning is mainly done to obtain quality fruit production. Training and pruning operations are essential in perennial fruit crops to optimize the light distribution, minimize the insect pest and diseases attack and for production of fruits of optimum quality. Training and pruning operations play a significant role in obtaining regular and prolific quality fruit production. The size, color, nutritional quality, and postharvest shelf life of fruits are all significantly affected by the training and pruning operations done during the preharvest stages in orchard. This chapter provides an insight into the basics of training and pruning systems and how they affect the postharvest fruit quality.

Leaf, panicle and fruit blight of litchi (Litchi chinensis) caused by Alternaria alternata in Bihar state, India

Abstract India is one of the leading litchi (Litchi chinensis Sonn.) producing countries in the world. A leaf blight on litchi was observed in April 2012 on nursery plants at Muzaffarpur, Bihar, India. Light to dark brown necrosis starting from leaf tips resulted in complete drying of leaves. Blighting of panicles and fruits were also noticed during April–June, 2014. Panicles dried out as a result of necrosis, while necrosis of pedicels led to complete drying of the rind of developing fruits. Infected tissues collected from different sites in diseased fields were cultured on potato dextrose agar (PDA), and the pathogen was identified as Alternaria alternata (Fr.) Keissler on the basis of morphological and cultural characteristics. The fungus produced greyish-black colonies on PDA with obclavate or obpyriform conidia in chains. Conidia had 1–4 transverse and 0–3 longitudinal septa, and measured 16–40 × 4–13 μm. Morphological identification was confirmed by sequencing the internal transcribed spacer (ITS) region of rDNA using ITS1 and ITS4 primers. Pathogenicity tests indicated that A. alternata infected and caused blights of the leaves, panicles and fruit of litchi. Alternaria alternata has been reported to cause post-harvest decay of litchi fruit, but this is the first report of A. alternata causing blights of leaves, panicles and fruit in the field.

Tissue Culture: Present Scenario and Future Prospects in Litchi Management

The present context elaborates the potential of tissue culture in production of quality planting materials in litchi (Litchi chinensis Sonn.). The plant is native to China but also grows well in India, Vietnam, Thailand, Taiwan, parts of Africa, Israel, Australia and at higher elevations in Mexico and Central and South America. However, its commercial cultivation is limited to only a few subtropical countries in the world due to its specific climatic requirements. With increased commercial importance coupled with rapid expanding market at both the national and international level, it is imperative to assure sufficient production of quality planting materials in litchi. In this review several in vitro culture techniques in litchi will be highlighted.

Systemic Information for Future Perspectives in Litchi Crop Improvement

Litchi (Litchi chinensis Sonn.) is a subtropical evergreen fruit crop of the Sapindaceae family. Over the years, significant growth in production and productivity coupled with the fast-expanding market of litchi has been recorded at both the national and international level. Most commercial cultivars in litchi have been clonally selected under Chinese or Indian conditions and have been adapted to a limited climatic condition. Disease infestation in litchi has been a long-term debate in the horticulture and agriculture sector. Keeping the damage factor as a prime concern, clonal selection as the basis of cultivar selection must rely on limited characteristics such as systemic susceptibility in terms of fruit size, quality, and period of maturity, which narrows down the diversity, focusing on only a few commercial traits. Hence, creation of variability within the litchi gene pool is of paramount importance to yield desirable characters such as precocity, dwarfness, regularity of bearing, wider adaptability, and resistance and avoidance of pests and disorders. The heterozygosity of litchi produces a wide extent of variability, which serves as the baseline for new selections through harnessing precocious genes and exploiting natural hybrid vigour and other genetic manipulations. Different strategic efforts on a breeding programme need to be undertaken on a large scale with considerations of a comprehensive survey of various genotypes and trait inheritance patterns, raising a large population of open pollinated seeds with known parentage, mutation breeding because of obvious difficulties with traditional litchi breeding and the lack of pure lines. This context provides the basic information for further improvement and genetic enhancement of the breeding programme in litchi disease resistance.

Important Diseases of Litchi and Their Management

Litchi (Litchi chinensis Sonn.) is a juicy fruit belonging to the Sapindaceae family and is one of the most important evergreen fruit trees. Diseases are one of the constraints on the production of litchi fruits. They indirectly reduce yield by debilitating the tree and directly reduce the yield or quality of fruit before and after harvest. Diseases are more important after harvest, although undoubtedly many of the fruits are infected before picking. Some of the pathogens infect leaves, flowers, and fruit, and a few others are associated with tree decline and tree deaths. Some pathogens also affect multiple phenophases of this fruit crop. So far, only diseases caused by fungal pathogens have been reported. This chapter provides information on the major diseases of litchi in terms of their importance, symptoms, and management strategies.

Pummelo in Homestead Garden: Conservation through Family Farming

The pummelo (Citrus grandis Merr.), the largest fruit size in citrus species, is an underutilized fruit in India. Pummelo in Bihar is mostly grown as homesteads and this fruit is to be developed as potential table fruit because of thick rind, easy to handle and transport. Genetic diversity is an important factor in any crop improvement programme for obtaining high yielding cultivars. Variation among seedling progenies is a rule in pummelo since it is monoembryonic Citrus spp. This study was conducted through four cell analysis in the five project communities under the UNEP-GEF project at the Pusa Site, Bihar during 2012 with aim for estimation of genetic diversity for physico-chemical traits, selection of superior clones and to draw the interrelationships between observations for precise characterization of pummelo seedling. Superior plants were also identified based on the highest yield i.e. number of fruits/ plant (> 300). Statistical analysis for physico-chemical parameters revealed significant differences among the selected plants for the 12 horticultural traits indicating the higher variability. Principal Component Analysis (PCA) and cluster dendrogram performed on the basis of studied parameters showed continuous variation in the fruit physico-chemical traits and many groups were formed, indicating existence of large and continuous variation. The first four PCs contributed 68.30% of the variability for fruit quality and PC1 accounted for 30.44% (acidity percentage) followed by fruit length (PC2), fruit width (PC3) etc. The maximum coefficient of variation was found in in case of rind thickness, 100 seed weight and acidity percentage. A large number of variability of pummelo with seedling origin and monoembryonic helps in identification of 4 pummelo clones for pulp colour (2 each for dark red flesh and pink flesh) with excellent eating quality, 9 superior clones were identified for profuse bearing with red fleshed and early. The above variation in the selected pummelo seedlings can be exploited for development of superior varieties, marketing and maintenance of exiting superior clone and above all grower can be ensured livelihood security through homestead farming practices in the community.

Genetic diversity in seedling populations of Mango

The genetic improvement of mango (Mangifera indica L.), a native of India, has been largely through selection among seedling populations or propagating elite clones and such efforts have resulted in the identification and cultivation of improved commercial varieties. Development of better cultivars by traditional method using morphological traits, although highly heritable, is slow because of long juvenility and being expensive. Farmers of Pusa, Bihar have been conserving high levels of intraspecific diversity of mango in old orchards mostly located along the Gandak River. These orchards are often poorly maintained as revenues obtained are small compared to income from other farm activities; however these old orchards harbour a highly diverse population of traditional mango varieties and seedlings, with trees over 80 years old. Hence a survey was conducted in five communities for documenting the mango diversity found in native landraces. Sixteen superior mango varieties of endemic value and importance were evaluated for table, sucking and pickling purposes on the basis of physical appearance and chemical attributes. Out of these, six were found suitable for table, five for sucking, three for pickle and two for dual purpose (sucking and table). Studies revealed a clone from Bhuskaul community with fruit weight up to 420.0 g with TSS 27.400B and having very thin stone and maturing by the end of August. The present study highlights the need for and demands of diversity rich areas of Pusa community in Bihar to conserve and protect seedling mangoes for the benefit of posterity with high value traits for future promotion. Furthermore, the characterization work was captured in fruit catalogues and shared back with the farming community, which might have increased the awareness, interest and appreciation of the available mango diversity and the interest in the continuation of these old highly diverse mango orchards for home use and to explore the commercial potential of these orchards and various types.

Climate Resilient Adaptation Strategies for Litchi Production

Litchi is very fastidious in its climatic requirements. Its cultivation and commercialization globally has therefore been at slow pace due to this stringent requirement. It is observed that there is poor as well as erratic bearing pattern in trees in many important litchi-growing areas. The growth, panicle emergence time, flowering behaviour and flowering phase have been found to be influenced by the impact of climatic change. The productivity/yield and quality fruit production have also been found to be very much affected by environmental parameters like temperature, photoperiod/light intensity, moisture content in the soil and humidity in the atmosphere.