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The Sixth Deans' Committee Recommendations have led to a thorough revision of the B.Sc (Hons) Ag, Plant Pathology program and has rendered existing text books incomplete for students. The course content has to be rewritten to comply with the NEP-2020 requirements for the new academic framework. This book of Diseases of Field Crops & Horticultural Crops & their Management is carefully restructured for undergraduate class and is completely in accordance with the latest 6th Deans’s Committee Recommendations Guidelines.The objective of writing this book are to study the symptoms produced on the host, study the etiology of the diseases, know about the disease cycle of the pathogens during pathogenesis, study the epidemiological factors responsible for disease development and study the management techniques for curbing the major diseases of field and horticultural crops. The main features of this volume are as follows: • The chapter "Fun Time" will sets the tone by addressing general terminology which also relate to the subject. Fun time is good ice breaker and prepares the students for the information to follow . • The subject matter has been presented point wise and step by step with suitable examples. • Efforts have been made to provide recent information. • The book has 39 chapters that cover the entire syllabus of course at the undergraduate level in Agriculture universities.

1. Blast Diagnostic Symptoms • Pathogen attacks the crop at all stages of crop growth. • Symptoms appear on leaves, nodes, rachis, and glumes. On the leaves, the lesions appear as small bluish green flecks, which enlarge under moist weather to form the characteristic spindle shaped spots with grey centre and dark brown margin (Leaf blast). • Spots coalesce as the disease progresses and large areas of the leaves dry up and wither. Severely infected nursery and field appear as burnt.• Black lesions appear on nodes girdling them. The affected nodes may break up and all the plant parts above the infected nodes may die (nodal blast). • During flower emergence, the fungus attacks the peduncle and the lesion turns to brownish-black which is referred to as rotten neck / neck rot / panicle blast (neck blast). • In early neck infection, grain filling does not occur while in late infection, partial grainfilling occurs (Fig.1).

Rust The rust of wheat has been studied more than any other disease in the world. K.C. Mehta and colleagues conducted exceptional research on the disease in India. There are three recognized wheat rusts. These include Puccinia graminis tritici, which causes black stem rust; Puccinia recondita, which causes brown rust (leaf rust); and P. striiformis, which causes yellow rust. Considering their later seasonal arrival, brown and yellow rusts inflict more damages than black rust. 1. Black or Stem Rust Diagnostic Symptoms • Symptoms are produced on almost all aerial parts of the wheat plant but are most common on stem, leaf sheaths. • Brown pustules of uredina appear on lower surface of the leaves, leaf sheaths and the stems, and on the spikes. which give them a rusty appearance. • Uredina form urediniospores , which are the repeating spores. • Uredina gradually start producing teliospores and finally transform into telia.

Banded Leaf and Sheath Blight Diagnostic Symptoms • From the crop’s seedling stage until crop maturity, this pathogen can infect the plant at any point in its growth. • The disease initially appears on the first and second leaf sheaths above the ground, and it eventually spreads to the ears, where it results in ear rot. • The hallmark symptoms of ear rot include the presence of light brown, cottony mycelium on the plant’s ear, small, rounded black sclerotia, early ear drying, and caking of the ear sheath. • When there is humidity, the infection that first appears on the lower sheath extends to the upper sheaths, causing leaf sheath rot and complete leaf drying. • When the condition worsens, the majority of the plant’s leaves become blighted, and easily detachable sclerotia form on the lesions. • The disease manifests as a straw-colored, wet, irregular to roundish patch on both leaf surfaces on the basal sheath.

Loose Smut Sphacelotheca cruenta Diagnostic Symptoms • Affected plants can be detected before the ears come out. • Shorter than the healthy plants with thinner stalks and marked tillering. • Ears come out much earlier than the healthy. • Glumes are hypertrophied and the ear head gives a loose appearance than healthy. • Sorus is covered by a thin membrane which ruptures very early, exposing the spores even as the head emerges from the sheath(Fig-1). Etiology Scientific Classification Kingdom : Fungi Division : Eumycota

1. Downy Mildew (Green Ear) Sclerospora graminicola Diagnostic Symptoms • Characteristic symptoms of the disease are pale, chlorotic, broad streaks extending from base to tip of leaves. • At the advancement of disease, the leaf streaks turn brown and the leaves become shredded longitudinally. • In severe infection, the downy fungal growth can be seen on the upper as well as lower surface of the leaves. • Infected plants fail to form ear but if formed, they are malformed to green leafy structures. • Complete ear can be transformed into leafy structure. • Pathogen transformed all floral parts such as glumes, palea, stamens and pistils into green linear leafy structures of variable lengths and no grains are produced. • Partial infection of ear head is observed in which some grains are produced and rest of the ear head is converted in to a green ear(Fig-1).

1. Blast Pyricularia grisea Diagnostic Symptoms • Crop is susceptible to the disease during all stages of its growth, from seedling to grain formation stage. • In young seedlings, lesions are generally of spindle shaped, however lesions of different sizes may also be observed. • In the beginning the spots have yellowish margin and grayish centre. Later, the centres become whitish grey and disintegrate. • Lesions are isolated in the beginning and afterwards they may soon coalesce. The distal portion of the leaves beyond the lesions may hang and drop off. • In older plants, the disease appears on leaf blades with typical spindle shaped spots. • Under congenial conditions, such spots enlarge, coalesce and form bigger lesions. • Lesions are like those on the seedlings and are about 0.3-0.5 cm in breadth and 1-2 cm in length. Apices of the infected leaves beyond the lesions hang down and sometimes break. • Stem infection causes blackening of the nodal region, penetrating into the tissues.

Tikka or Leaf Spot Cercospora arachidicola/ Phaeoisariopsis personatum Diagnostic Symptoms • Disease is caused by two different pathogens, namely, Cercospora arachidicola and Phaeoisariopsis personatum. • The two pathogens mostly occur on the same leaves. • The Cercospora arachidicola appears about a month earlier than the Phaeoisariopsis personatum. • The two pathogens cause symptoms differing each other. Early leaf spot • Sub-circular dark brown spots having 1 to over 10 mm diameter are produced on the upper leaflet surface. • Spots are of lighter shade of brown on the lower side of the leaflets. • Yellow halo is seen around the brown spots. • Dark brown in colour on the upper leaflet surface where most sporulation occurs and a lighter shade of brown on the lower leaflet surface.

1. Rhizoctonia aerial blight / Web blight Symptoms • The soybean Rhizoctonia aerial blight is a damaging foliar disease that quickly defoliates plants in warm, humid climates. • Rhizoctonia solani causes soybean aerial blight, which manifests as leaf and pod spots, leaf blight, defoliation, lesions on the stem and petiole, a mycelium that resembles a cobweb, and sclerotia that form on diseased leaves. • The plant’s lower or central sections are where infection starts, and it progressively spreads upward. • The leaves first have wet patches that eventually become green to reddish brown in color before turning tan, brown, or black. • Small spots at first eventually combine to cover a significant portion of the leaf. • Affected leaves droop and stick to the pods and stem underneath them during the aerial blight phase, infecting the pods and seeds in the process.

Ascochyta Blight Diagnostic Symptoms • All above ground parts of the plant are infected. • Round or elongated lesions, bearing irregularly depressed brown spot and surrounded by a brownish red margin on leaf. • Similar spots may appear on the stem and pods. • Spots on the stem and pods have pycnidia arranged in concentric circles as minute black dots. • When the lesions girdle the stem, the portion above the point of attack rapidly dies. • If the main stem is girdles at the collar region, the whole plant dies (Fig.1). Etiology Scientific Classification Kingdom : Fungi Division : Eumycota

Downy Mildew Diagnostic Symptoms • At first grayish white, moldy growth appears on the lower leaf surface, and a yellowish area appears on the opposite side of the leaf. • Infected leaves can turn yellow and die if weather is cool and damp. • Stems may be distorted and stunted. • Brown blotches appear on pods, and mold may grow inside pods(Fig-2). Etiology Scientific Classification Phylum :Heterokontophyta Class : Oomycota Order : Peronosporales Family :Peronosporaceae Genus :Peronospora  

Anthracnose Diagnostic Symptoms • Pathogen attacks all aerial parts of plants and at any stage of their growth. • Symptoms are circular, black, sunken spots with dark center and bright red orange margins on leaves and pods. • In severe infections, the affected parts wither off. • Seedlings get blighted due to infection soon after seed germination. • Infected pods have discolored seeds (Fig.3). Etiology Scientific Classification Kingdom : Fungi Division : Eumycota Sub- division : Deuteromycotina

Red Rot Diagnostic Symptoms • Practically all above ground parts are affected, but stalks are the main targets of stack. • Spindle leaves (third or fourth)starts drying. • Further stalks becomes discolored and hollow. • Diagnostic symptom is th formation of red streaks, interrupted by white patches , inside the stalk.This can be seen by splitting the stalks longitudinally. • White patches are characteristics of disease, not found in other stalk rots. • After splitting opened the diseased stalk, a sour smell due to conversion of glucose to alcohol. • Red longitudinal lesions are also seen on the mid ribs of the leaves on which black color fruiting body (Acervuli) are formed (Fig.1).

Alternaria Blight Diagnostic Symptoms • Symptom first appear on the lower leaves as small circular brown necrotic spots which slowly increase in size. • Many concentric spots coalesce to cover large patches showing blightening and defoliation in severe cases. • Circular to linear, dark brown lesions also develop on stems and pods, which are elongated at later stage. • Infected pods produce small, discolored and shriveled seeds( Fig.2). Etiology Scientific Classification Kingdom : Fungi Phylum : Ascomycota Class : Dothideomycetes

Sclerotinia Stem Rot Diagnostic Symptoms • Early symptoms of the disease are noticed forty days after sowing. • Stem is usually infected at or near the soil line. • Brownish lesion develops at the base of the stem and eventually girdles the plant. A white fan-like inoculum growth forms over the infected tissues and often radiates over the soil surface. • Silky appearance of plants can be spotted from a distance and a row effect can be observed in heavily infected soil. Later the entire plant withers and dies. • The lesion grows up the stem, destroying the cortical tissue and leaving the fibrous vascular strands as the tissues dry out. • White cottony mycelium and mustard seed type sclerotial bodies are conspicuous on the affected stem near soil level. This also causes collar rot in the seedling stage (Fig.2).

Anthracnose Diagnostic Symptoms • Pathogen infects the seedlings and produces small reddish circular spots on the cotyledons and primary leaves. • Lesions develop on the collar region, stem may be girdled, causing seedling to wilt and die. • In mature plants, the fungus attacks the stem, leading to stem splitting and shredding of bark. • Most common symptom is boll spotting. Small water soaked, circular, reddish brown depressed spots appear on the bolls. • The lint is stained to yellow or brown, becomes a solid brittle mass of fiber.The infected bolls cease to grow and burst and dry up prematurely(Fig-2). Etiology Scientific Classification Kingdom : Fungi Division : Eumycota

1. Gummosis. Diagnosic Symptoms • First symptoms are dark staining of bark which progresses into the wood. • Bark at the base is destroyed resulting in girdling and finally death of the tree. • Bark in such parts dries, shrinks and cracks and shreds in lengthwise vertical strips. • Later profuse exudation of gum from the bark of the trunk (characteristic symptom). • The infection spreads both upward to the leaves and even fruits and downward to the roots causing fibrous root rot. • The fibrous root rot destroys a major portion of the root system. • However, the trunck and root infections may usually result in ultimate drying of the tree (Fig-1). Etiology Scientific Classification Kingdom : Fungi Division : Eumycota

1. Sigatoka Diagnostic Symptoms • Early symptoms appear on the young leaves. • Small spindle shaped spots on foliage with greyish centreand yellowish halo running parallel to veins. • Spots are mostly seen along the edge of the leaf with defined margin and possess dark brown to black margin. Spots coalesce and whole leaf blade dries up. • On the upper surface of the spots, fructificationsof the fungus appear as black specks unevenly and individual bananas appear undersized and their flesh develops a buff pinkish colour, and store poorly (Fig. 1). Etiology Scientific Classification Kingdom : Fungi Division : Eumycota Sub- division : Deuteromycotina  

1. Stem rot / Foot rot/Collar rot Diagnostic Symptoms • The appearance of water-soaked spots on the stem close to ground level is what characterizes it. • The tissues degrade as a result of the fast enlargement of these patches, girdling the stem and turning it dark brown or black. • Strong winds cause these afflicted plants to topple over and eventually die. • If the disease attack is not too severe, the plants will still be stunted and only one side of the stem will decay. • If fruit develops, it is deformed and withered. • The plant eventually dies (Fig.1). Etiology • Pathogen: Pythium aphanidermatum. • Mycelium is colorless, slender, coenocytic, profusely branching and rapidly growing mostly intracellularly. • Sporangia terminal or intercalary produce a vesicle at the end of hyphal branch. • Zoospores biflagellate and reniform.

1) Bacterial Blight Diagnostic Symptoms • Bacterial blight of pomegranate was first reported in India from Delhi in 1952. • First water-soaked lesions develop on fruits within 2–3 days and appear as spots. • Initially, spots are black and round and surrounded by bacterial ooze. • Under favorable conditions, spots enlarge to become raised, dark brown lesions with indefinite margins that cause the fruit to crack. • Disease may cause up to 90% yield reduction (Fig.1). Etiology Domain : Bacteria Phylum : Proteobacteria Class : Gammaproteobacteria Order : Xanthomonadales

1). Scab Diagnostic Symptoms • Symptoms generally noticed on leaves and fruits. • Affected leaves become twisted or puckered and have black, circular spots on their upper surface. • On the under surface of leaves, the spots are velvety and may coalesce to cover the whole leaf surface. Severely affected leaves may turn yellow and drop. • Scab can also infect flower stems and cause flowers to drop. • Lesions later become sunken and brown and may have spores around their margins. • Infected fruit become distorted and may crack, allowing entry of secondary organisms(Figure-1). Etiology Scientific Classification Kingdom : Fungi Division : Ascomycota

1) Leaf Curl Taphrina deformans Disease Symptoms • Initially yellowish to reddish areas appear on leaf blade of young leaves in the spring. • These areas progressively thicken and pucker along the midrib causing the leaf to curl. • Infected leaves often develop red to purple color. Later on white to silvery coating of spores develop on the upper leaf surface and the affected leaves become crisp and brittle. • Finally, infected leaves abscise prematurely or may sometimes remain attached , gradually turning dark brown on severly infected trees. • Fruit infection is characterized by irregular, raised, wrinkled and reddish lesions. • Infected flowers and fruits drop rapidally(Fig-1).

1. Downy mildew Diagnostic Symptoms • Symptoms appear on all aerial and tender parts of the vine. • Irregular, yellowish, translucent spots on the upper surface of the leaves. • Correspondingly on the lower surface, dirty white, powdery growth of fungus appears. • Affected leaves become, yellow and brown and gets dried due to necrosis • Premature defoliation. • Dwarfing of tender shoots. • Infected leaves, shoots and tendrils are covered by whitish growth of the fungus. • White growth of fungus on berries which subsequently becomes leathery and shrivels. Infected berries turn hard, bluish green and then brown. • Later infection of berries results in soft rot symptoms. Normally, the fully grown or maturing berries do not contact fresh infection as stomata turn non-functional. • No cracking of the skin of the berries (Fig.1). 

1) Leaf Spot (Mycosphaerella fragariae teleomorph, Ramularia brunnea Peck anamorph). Disease Symptoms • Older leaves usually show purple spots (3-6 mm in diameter) on the upper surface, sometimes with a slightly darker halo. • As the spots mature, they become white to gray and surrounded by a brownish halo. • A typical lesions, uniformly brown without darker border or lighter centers, may form on young leaves. • Later on, the whole leaf is covered by numerous lesions and become chlorotic, withered and die. • Fruits are generally not directly infected, but the loss of foliage can reduce their quality and yield (Fig-1). Etiology Scientific Classification Kingdom : Fungi Division : Ascomycota Class : Dothideomycetes

1) Bud Rot Diagnostic Symptoms • Severe on young palms. • Yellowish green discoloration of the heart leaf or crown leaf. • The basal tissues of the leaf rot quickly and can be easily separated from the crown. • Spindle withers and droop down. • Older leaves develop irregular, water soaked spots which are sunken in nature. • The leaves and sheath in the central spindle fall off leaving an outer whorl of green leaves. • The withered central shoot can be pulled out very easily from the crown. • The central crown may rot and in few months the tree may wilt. • Young nuts fail to mature and fall (Fig.1).

1) Blister Blight Diagnostic Symptoms • Initially oily, yellowish, translucent spots appear on the tender leaf and turn to deep red shiny blisters. • The circular spot gradually enlarges to 3 to 13mm diameter, bulged on the under surface of the leaf with a concave trough like depression on the upper surface. • Leaves become curled and distorted. • First flush of 2-3 young leaves are attacked and the young shoots and buds are killed. • Mature leaf is not affected. • In nursery infection, seedlings are stunted with many thin stems instead of a single stalk. • Repeated attacks cause death of seedlings. • Badly affected nurseries will have to be abandoned. • Succulent leaves and green shoots of newly pruned tea are most susceptible (Fig.1). • Basidiospores cause secondary infection.

1) Rust Diagnostic Symptoms • The disease is restricted to leaves although sometimes it can seen on tender shoots and berries. • The rust pustules appear as small spots, 1-2 mm in diameter. • In early stages these spots are yellowish becoming orange in color with increase in size. • On the upper surface, opposite the spots on the lower surface , the color is often brownish. • In severe attack leaves may dry and wither. • The berries remain small and fail to ripen. • Extensive defoliation weakens the trees and results in poor yield, severe die back of twigs, and death of trees (Fig.1).

1. Anthracnose Colletotrichum gloeosporioides (Glomerella cingulata) Diagnostic Symptoms • Disease produces symptoms like leaf spot, blossom blight, withertip, twig blight and fruit rot . • Symptoms on leaves show as gray to brown spots with dark margins and a yellow halo. The spots later enlarge and coaleasce to form sizable necrotic areas. • Tender shoots and foliage are easily affected which ultimately cause die back young branches. • Blossom blight may vary in severity from slight to a heavy infection of the panicles . • Black spots develop on panicles as well as on fruits. Severe infection destroys the entire inflorescence resulting in no setting of fruits. • Young infected fruits develop black spots, shrivel and drop off. • Fruits infected at mature stage carry the pathogen into storage and cause considerable loss during storage, transit and marketing (Figure -1).

1. Early Blight Diagnostic Symptoms • Brown-black necrotic spot-angular, oval shape characterized by concentric rings . • The concentric ring produce a target board effect, the most characteristic symptom of the disease. • Several spot coalesce & spread all over the leaf. • In severe attacks leaves shrivel and fall down. • Infection and rotting of tubers has also been reported (Fig.1). Etiology Scientific Classification Kingdom : Fungi Phylum : Ascomycota

1. Damping off Diagnostic Symptoms • Disease occurs in two stages, i.e. the pre-emergence and the postemergence phase. • In the pre-emergence phase, the seedlings are killed just before they reach the soil surface. • The young radical and the plumule are killed and there is complete rotting of the seedlings. • The post-emergence phase is characterized by the infection of the young, juvenile tissues of the collar at the ground level. • The infected tissues become soft and water soaked. The seedlings topple over or collapse (Fig.1) Etiology • Pathogen; Pythium aphanidermatum. • The fungus has a characteristic mycelium, which coenocytic, hyaline, freely branching and thick hyphae. • It reproduces both asexually and sexually.

1) Phomopsis fruit rot or Blight Diagnostic Symptoms • Plants are attacked at all stages of growth. • On leaves, circular to irregular, clearly defined grayish brown spots having light centers appear. The diseased leaves become yellowish in colour and may drop off. • Several black pycnidiacan be seen on older spots. • Lesions on stem are dark brown, round to oval and have grayish centers where pycnidia develop. • At the base of the stem, the fungus causes characteristic constrictions leading to canker development and toppling of plants. • On fruits, small pale sunken spots appear which on enlargement cover entire fruit surface. These spots become watery leading to soft rot phase of the disease. A large number of dot like pycnidia also develop on such spots. • Infection of fruit through calyx leads to development of dry rot and fruits appear black and mummified (Fig.1).

1. Anthracnose or Fruit Rot and Die Back Diagnostic Symptoms The disease occurs in two forms: the die back and the ripe -rot Die back symptoms • Small, circular to irregular, brownish black scattered spots appear on leaves. • Severely infected leaves defoliate. • Infection of growing tips leads to necrosis of branches from tip backwards. • Necrotic tissues appear grayish white with black dot like acervuli in the center. • Shedding of flowers due to the infection at pedicel and tips of branches. Fruit symptoms • Ripe fruits are more liable for attack than the green ones. • Small, circular, yellowish to pinkish sunken spots appear on fruits.

1) Downy Mildew Diagnostic Symptoms • Yellow, angular spots restricted by veins resembling mosaic mottling appear on upper surface of leaves . • Corresponding lower surface of these spots shows a purplish downy xgrowth in moist weather. • Spots turn necrotic with age. • Diseased leaves become yellow and fall down . • Diseased plants get stunted and die . • Fruits produced may not mature and have a poor taste (Fig.-1). Etiology Scientific Classification Kingdom : Fungi Division : Eumycota

1. Alternaria leaf spot Diagnostic Symptoms • Spots are small, dark coloured. • They enlarge, soon become circular & 1mm. in diameter. • Under humid conditions groups of conidiophores will be formed in the spot. • Spots develop concentric rings. • Finally the spots coalesce leading to blighting of leaves. • Pathogen is seed borne and cause shriveling of seeds and poor germination. • Linear spots also appear on petioles, stems, pods & seeds (Fig.1).

1) Anthracnose Diagnostic Symptoms • All the above ground parts are affected. However, the characteristic symptoms appear on pods. • On cotyledons, spots are sunken dark brown or black with pink spore mass. • Seedling infection results in collapse of seedling. • Spots on leaves appear on lower side and are black. Later these may also appear on upper surface. When the infection is severe, the affected plants wither off. • Black, sunken, circular spots of varying sizes appear on pods with bright red, yellow or orange margins. The centre of these spots later turns grey or pink due to sporulation of the pathogen. The border of these spots appear raised (Fig.1).

1. Vein-Clearing/Yellow Vein Mosaic Bhendi yellow vein mosaic virus Diagnostic Symptoms • Yellowing of the entire network of veins in the leaf blade is the characteristic symptom. • In severe infections, the younger leaves turn yellow, become reduced in size and the plant is highly stunted. • The veins of the leaves will be cleared by the virus and intervenal area becomes completely yellow or white. • In a field, most of the plants may be diseased and the infection may start at any stage of plant growth. • Infection restricts flowering and fruits, if formed, may be smaller and harder. • The affected plants produce fruits with yellow or white colour and they are not fit for marketing (Fig.1). • The virus is spread by whitefly.

1) Leaf Spot Diagnostic Symptoms • Initially oblong brown spots having about 4-5 cm in length and 2-3 cm in width with grey centres surrounded with yellow hallo are found on the leaves. • Large number of spots may be found on a single leaf and as the disease advances, spots enlarge and cover a major portion of leaf blade. • Severly affected plants dry and wilt. • Black dots acervuli formed in concentric rings on spot.The grey centres become thin and get teared(Fig-1). Etiology Scientific Classification Kingdom : Fungi Division : Eumycota Sub- division : Deuteromycotina

1). Stem Gall Diagnostic Symptoms • Symptom appears in the form of tumor-like swellings of leaf veins, leaf stalks, peduncles, stems as well as fruits. • Infected veins show a swollen hanging appearance to the leaves. • Initially the tumors are glossy which rupture later on and become rough. They are about 3 mm broad and up to 12.5 mm long. • Badly affected plants may be killed. • In the presence of excessive soil moisture, especially under shaded conditions, when the stem fails to harden and remain succulent, the tumors are numerous (Fig-1). Etiology Scientific Classification Kingdom : Fungi Division : Ascomycota Class : Taphrinomycetes Order : Taphrinales

1) Botrytis Gray Mould Diagnostic Symptoms • Appearance of a gray, fuzzy mold leaves, stems and on flowers of or plants. Also called, “gray mold”. • Spotting or blight on leaf and flower stem lesions, and dieback. • Flower parts become necrotic and die(Fig-1). Etiology Domain : Eukaryota Kingdom : Fungi Division : Ascomycota Class : Leotiomycetes Order : Helotiales Family : Sclerotiniaceae  

1) Powdery mildew Diagnostic Symptoms • A white, powdery fungal growth on the upper, lower or both leaves and shoots. • There may be discolouration of the affected parts of the leaf, and heavily infected young leaves can be curled and distorted. • Mildew growth may also be found on the stems, flower stalks, calyces and petals. • Heavily infected flower buds frequently fail to open properly. • Mildew growth on stems and flower stalks is usually thicker and more mat-like than that on the leaves. • Mildew growth on all parts may turn browner as it ages (Fig-1).