B. M. K UMAR
5.4 Fruit-tree Diversity in Kerala Homegardens
While progress in modern agriculture has been through monospecific stands, sometimes described as ‘biological deserts’ of low species diversity, the tropical
homegardens are spectacular examples of fruit-tree richness and diversity. Almost all types of fruit crops, ranging from tropical evergreen to temperate deciduous types, are grown. Overall, 69 fruit- and nut-yielding trees accounted for more than 30% of all tree species observed in field surveys conducted in Kerala (Kumaret al., 1994; Patil, 2005). Prominent examples include mango (Mangifera indica) – the ‘king of fruits’ – and many underutilized fruits such as jackfruit (Artocarpus heterophyllus), aonla or Indian gooseberry (Emblica officinalis), bael (Aegle marmelos), custard apple (Annona squamosa), jamun (Syzygium cuminii), karonda (Carissa congesta) and tamarind (Tamarindus indica). Many of these have good nutritive value and attract considerable local demand (Pareek and Sharma, 1993). Exotic fruits such as papaya (Carica papaya), guava (Psidium guajava), pomegranate (Punica granatum) and cashew (Anacardium occidentale) are also important. The relative proportions of individual species found within the homegardens, however, are variable (Table 5.1).
Each homegarden owes its unique appearance to its history, species diversity and physical arrangements. None the less, most of the gardeners included in the surveys showed a propensity to grow fruit and nut trees.
Therefore it is not surprising to find each garden characterized by the presence of tall native and exotic fruit trees such as coconut, mango, jackfruit, guava and plantains. This, however, does not imply that the fruit-tree composition of all homegardens within a region is alike or static. Indeed, the species assemblages are strongly influenced by the specific needs and preferences of each household, including the tastes of household members, food culture and local customs, nutritional complementarity with other major food sources, and ecological and socio-economic factors such as market forces, policies and local development projects (Kumar and Nair, 2004). These factors probably make the fruit-tree composition of the homegarden a transient phenomenon.
5.4.1 Temporal dynamics in major homegarden components
Table 5.1 summarizes the macro-level changes in major fruit trees (both indigenous and exotic) of Kerala homegardens over a 10-year period between 1992–1995 and 2002–2004. Although the data presented are not strictly comparable because of the disparate nature of the sampling units and intensities, the number of fruit-tree taxa in the homegardens has apparently increased over time. For example, 29 additional species were encountered in the 2002–2004 survey over the previous period, and another 24 species increased their presence. None the less, for as many as 41 of the 69 fruit and nut trees listed in Table 5.1, the increases in relative proportion of homegardens were rather modest, while one decreased, and data on three species are not available. The implicit temporal variations in garden composition probably reflect the processes of rural transformations that influence homegarden structure, composition and dynamics (Peyre et al., 2006; Wiersum, 2006).
Kumar and Nair (2004) summarized the work on homegarden variability and reported that both temporal and spatial variations in species diversity and plant density are probable, even within the same geographical/eco-climatic region.
B.M.Kumar Frequency (%)
Species Mid-1990sa
Botanical name Common name Mean Ranged Mid-2000sb Changec
Indigenous
Aegle marmelos(L.) Corr Bael fruit 7.5 3.7–26.7 5 0
Alangium salviifolium(L. f.) Wang. Sage-leaved alangium 0.5 0 2 0
Areca catechuL. Arecanut 55.3 16.7–93.3 79 +
Artocarpus gomezianusWall. ex Trecul Monkey jack 0.5 0 6 0
Artocarpus heterophyllusLam. Jackfruit 69.8 30.4–100. 95 +
Artocarpus hirsutusLam. Wild jack 30.6 3.8–79.5 44 +
Azadirachta indicaA. Juss. Neem 0.5 0 22 +
Borassus flabelliferL. Palmyra palm 12.5 2.5–61.5 2
Calophyllum inophyllumL. Alexandrian laurel 9.2 2.5–13.6 4 0
Carissa carandasL. Karaunda 0.5 0 3 0
Chrysophyllum lanceolatum(Blume) A. DC. Star apple 0.5 0 6 0
Citrusspp. 14.4 1.7–33.3 47 +
Cocos nuciferaL. Coconut 92.2 46.2–100. 98 0
Emblica officinalisGaertn. Indian gooseberry 15.9 2.3–83.9 30 +
Ficus racemosaL. Guler. Cluster fig 0.5 0 9 0
Flacourtia montanaGrah. Charalpazham 0.5 0 9 0
Garcinia gummi-gutta(L.) Robs. Kudampuli 15.6 3.2–37. 37 +
Garcinia indica(Thouars) Choisy Kokkam butter 1.8 1.7–1.9 0 0
Grewia tiliifoliaVahl. Chadachi 9.1 6.7–13.3 7 0
Hydnocarpus pentandra(Buch.-Ham.) Oken Marotti 11.3 1.7–40 4 0
Madhuca longifolia(Koenig) J.F. Macbr. Mahua tree 0 0 1 0
Mangifera indicaL. Mango 75.6 35.3–100 90 +
Mimusops elengiL. Spanish cherry 0.5 0 11 +
Moringa oleiferaBedd. Drumstick 15.3 3.3–36.2 73 +
Morus albaL. Mulberry 10.2 1.7–33.3 8 0
Myristica malabaricaLam. False nutmeg 0.5 0 4 0
ree Production89
Prunus ceylanica(Wight) Miq. Saberjelli 0.5 0 1 0
Sapindus emarginatusVahl. Soapnut tree 7.5 2.5–20. 2 0
Semecarpus anacardiumL.f. Marking-nut tree 6.7 0 0 0
Spondias pinnata(L.f.) Kurz. Indian hog-plum 12.5 3.2–40. 19 0
Syzygium cuminii(L.) Skeels. Malabar plum 7.7 2.5–21.4 17 0
Syzygium jambos(L.) Alston. Malabar plum 15.5 12.1–20... 30 +
Terminalia bellirica(Gaertn.) Roxb. Belliric myrobalan 8.2 2.5–13.3 8 0
Exotic
Anacardium occidentaleL. Cashew 35.8 6.7–93.3 59 +
Annona muricataL. Soursop 5.5 2.3–7.5 4 0
Annona reticulataL. Bullock’s heart 4.7 2.3–6.7 26 +
Annona squamosaL. Custard apple 16.5 6.7–27.5 14 0
Artocarpus communisJ.R. & G. Forst. Breadfruit 15.2 6.5–37. 41 +
Averrhoa bilimbiL. Bilimbi 13.1 1.7–31.3 26 +
Averrhoa carambolaL. Carambola 0.5 0 1 0
Bixa orellanaL. Annatto tree 7.5 1.7–13.3 1 0
Carica papayaL. Papaya 19.8 5.2–66.7 71 +
Chrysophyllum cainitoL. Star apple 0.5 0 6 0
Cinnamomum camphora(L.) Presl. Camphor tree 0.5 0 16 +
Citrus grandis(L.) Osbeck. Pummelo 0.5 0 9 0
Citrus reticulata Blanco Mandarin orange 0.5 0 1 0
Citrus sinensis(L.) Osbeck. Thick-skinned orange 0.5 0 5 0
Coffea arabica Coffee 8.2 2.5–20. – *
Elaeis guineensisJacq. African oil palm 0.5 0 1 0
Eugenia unifloraL. Surinam cherry 0.5 0 2 0
Ficus caricaL. Anjur 0.5 0 1 0
Garcinia mangostanaL. Mangosteen 0.5 0 7 0
Malpighia punicifoliaL. West Indian cherry 0.5 0 2 0
Manilkara zapota(L.) P. Royan Sapota 12.5 2.5–21.4 24 +
Myristica fragrans Houtt. Nutmeg 12.7 1.9–33.3 27 +
Continued
B.M.Kumar Frequency (%)
Species Mid-1990sa
Botanical name Common name Mean Ranged Mid-2000sb Changec
Persea americanaMill. Avocado 0.5 0 3 0
Phyllanthus acidus(L.) Skeels Star gooseberry 13.9 3.4–25. 14 0
Pimenta officinalisLindl. Allspice 0.5 0 14 +
Pithecellobium dulce(Roxb.) Benth. Bread and cheese tree 0.5 0 1 0
Pouteria campechiana(Kunth.) Baehni Egg fruit 0.5 0 17 +
Psidium guajavaL. Guava 31.1 6.7–70. 84 +
Psidium cattleyanumWeinw Red strawberry guava 0.5 0 1 0
Punica granatumL. Pomegranate 0.5 0 5 0
Syzygium aromaticum(L.) Merr. & Perry Clove 8.5 2.3–17.4 12 0
Syzygium malaccensis(L.) Merr. & Perry Malay apple 0.5 0 30
Tamarindus indica L. Tamarind 32.9 6.7–48.1 66 +
Terminalia catappaL. Barbados almond 8.9 2.3–21.4 18 +
Theobroma cacao L. Cacao 8.1 1.7–20. – *
aSurvey conducted during 1992–1995, includes data on the 252 farms reported by Kumar et al. (1994) supplemented with 333 additional farms (B.M. Kumar, 1995, unpublished results; total respondents = 585).
bSurvey of 100 farms in Kerala, which constitutes a subset of the 544 samples enumerated by Patil (2005) during 2002–2004 from three South Indian States.
cShift in magnitude less than 10% in either direction is ignored (‘0’), more than 10% increase in frequency is ‘+’, and more than 10%
decrease is ‘’. * Indicates species such as cacao, plantains and coffee, which were not enumerated in the 2002–2004 survey.
dRange of values for different thaluks(strata) during the first sampling.
5.4.2 Genetic diversity of indigenous fruit trees
Aside from floristic richness, several of the indigenous fruit trees exhibit considerable intraspecific variations in tree growth, phenology of flowering, and fruit characters (Table 5.2). This is consistent with the observations of Watson and Eyzaguirre (2002), who reported that several landraces and cultivars, as well as rare and endangered species, are preserved in homegardens. Contemporary patterns of genetic variation in homegarden components, however, reflect the historical processes associated with domestication, such as the geographical origin(s) of the cultivated populations, interpopulation genetic exchange and ancestry, which influence the genetic structuring of such populations (Schaal et al., 1998). However, in view of the complex patterns of germplasm exchange prevailing in many indigenous cultures and the multiple origins of cultivated plant populations, it is difficult to make firm generalizations. Furthermore, only limited research on population genetics and systematics, in order to characterize this diversity and understand the mechanisms through which it arises, has been done in Peninsular India. The high degree of genetic diversity observed in the Kerala homegardens (Table 5.2), nevertheless, ensures compliance with the Convention on Biological Diversity (CBD) on aspects such as ex situbiodiversity conservation.
5.4.3 Utilizing and conserving homegarden genetic resources
In certain cases, the rich genetic diversity of fruit trees has been utilized in clonal selection programmes, which have led to the development of many commercial varieties. For example, in mango about 30 varieties have been developed in India (Ghosh, 1998). However, traditional mango varieties in the homegardens of Kerala, which constitute an important segment of the genetic diversity of this crop (Anila and Radha, 2003), have been largely ignored by organized research. Due to commercialization, many of these cultivars are also disappearing (Kumar and Nair, 2004), which calls for urgent steps to be taken to conserve the indigenous germplasm. Jackfruit, another important product of Kerala homegardens, grows wild in the forests of the Western and Eastern Ghats of India, besides being cultivated as a horticultural crop (Ghosh, 1998). Being cross-pollinated and mostly seed-propagated, it exhibits great variations in fruit characteristics such as density of spikes on the rind, periodicity of bearing, size and shape, quality, and period of maturity (Melantha, 1998). Here too, selections involving culinary/table types with superior traits have been attempted (Ghosh, 1998), but no major conservation efforts to preserve the native populations are in the pipeline.