SUMMARY

Four genotypes of Hevea brasiliensis namely GT-1, PR-107, PRIM-600 and non graft clones were studied for latex yield during the year 1988 to 1993. The non graft clone showed the most promising yield performance (95 ml/tree/tapping) followed by GT-1 (62 ml/tree/trapping). The four genotypes varied remarkably for the sensitivity to climatic factors. In GT-1 the latex yield was positively correlated with maximum temperature and negatively correlated with minimum temperature and humidity. In non graft clone high temperature favour maximum yield and minimum temperature affected latex yield. The dependence of latex yield on climatic factors prevailing during year satisfactorily evaluated in non graft clone and GT-1. Hence these two types are considered suitable for Konkan region.

Hevea brasiliensis is the principle source of natural rubber. Latex secretion occurs from laticiferous vessels situlated in the zone of secondary phloem and its flow towards cut end is known to be governed by several physiological factors (Sethuraj, 1990). Turgor pressure is regarded as a main driving force behind latex flow (Jacob et al.1990) which is sensitive environmental factors, especially the soil moisture status. Ambient temperature and relative humidity are the important climatic factors involved in maintaining the gradiant for soil-plant-atmosphere continuum of water are therefore expected to affect the turgor pressure and ultimately the latex yield.

The current investigation is aimed at assessing the latex yield performance of four genotypes of para rubber with reference to variation in temperature and humidity in Konkan region of Maharashtra.

MATERIALS AND METHODS

Three rubber varieties namely GT-1, PRIM-600 and PR-107 raised from the grafts alongwith a non graft clone raised from seeds planted during the year 1978 constituted the experimental material. The plantation was done at spacing of 16’X16’ over area of 0.60 hectre at Research Farm of Botany Department, Konkan Krishi Vidyapeeth, Dapoli.

The cultural practices as per recommendation made by Rubber Board, Kottayam were followed. The plantation block was not irrigated during the post mansoon season. The tapping of latex commenced from the year 1988. The latex yield per tapping was recorded for individual trees. The data on latex yield in relation to climatic factors namely maximum temperature, minimum temperature, relative humidity, sunshine hours and rainfall were analysed statistically according to the method given by Gomez and Gomez (1985).

RESULTS AND DISCUSSION

The average latex yield/tapping of the individual trees of 3 genotypes of rubber and a non graft clone from the year of commencement of tapping (1988-89) for five years (1992-1993) is given in Table-1. It is revealed that in the average latex yield of four genotype during initial sharply (64.39 ml) and remained steady during fourth year. In fifth year (1992-93) it reached as high as 83.15 ml/tree/tapping. Thus the latex yield increased gradually from commencement of tapping. Among the four genotypes non graft clones raised from seeds showed highest average latex yield tree/taping 95.95ml Over five years. The variety GT-1 showed second ranking position (61.97ml) followed by PRIM-600 (53.79ml), with lowest performance of PR-107.

Average latex yield (ml/tree/tapping) of four genotypes of rubber during initial five years of tapping

The latex yield per tapping of the four genotypes in each of the fortnight from June to April end of 1992-93 are given in Table-2. It is noticed that during June to August the latex yields were very low. During September a sharp rise was noticed giving more than 100 ml latex/tapping in all the four genotypes. During October and November the latex yield dropped down noticeably. December and January tapping exhibited substantially high latex yield. From February onwards the latex yield declined gradually.

Latex yield of hevea in relation to climatic factors in Konkan region

Thus, it is clear that the latex yield in Hevea is sensitive to seasonal variation. This variation is obviously on account of fluctuations in climatic factors according to change in season. The relationship of latex yield to various climatic factors can be ascertained with correlation analysis from Table-3. It is revealed that in GT-1 the latex yield is positively correlated with minimum temperature and relative humidity. This clearly indicates that warm climate is very favourable for latex yield in GT-1. The dry cool climate reduces the yield drastically. In non graft clones also the latex yield were positively correlated with maximum temperature and negatively correlated with minimum temperature this again suggested the low temperature are unfavorable for latex yield. Importantly relative humidity did not show correlation with yield in non graft trees. In PR-107 and PRIM-600 the latex yield had no association with temperature and relative humidity. The negative association with temperature and relative humidity. The negative associations of latex yield with sunshine hours in PR-107 warrants the importance of bright sunshine in determining the latex yield of Hevea.

Correlation coefficients of latex yield (ml/tree) of different genotypes of Hevea with climatic parameters

* Significant at 5%

** Significant at 1%

The multiple regression equation fitted for explaining the dependence of latex yield on different climatic factors on four genotypes of Hevea are given in Table-4. It is revealed that in GT-1 67% variation in latex yield was extended by the climatic factors prevailing during the year. In non graft clones more than 73% variation in latex yield was explained by climatic factors during year under consideration. In PR-107 and PRIM-600 the magnitudes of the coefficients of determination (R²) were very poor (0.29 and 0.13 respectively). This clearly indicated the unsuitability of these two genotypes in climatic condition of Konkan region. From foreign discussion it is clear that the latex yield increase gradually with advancement of age of trees. The genotypes vary in respect of latex yield potentials and sensitive to climatic factors. The non graft clone have most promising performance followed by GT-1. For climatic conditions of Konkan region the non graft clone and GT-1 should consider as most suitable types.

x₁ = Max.Temp.
x₂ = Min.Temp.
x₃= Humidity
x₄= Sunshine
x₅= Rainfall

REFERENCES

Gomez K.A. and Gomez A.A. (1983) Statistical procedures for Agricultural Research. Second Edition. Published by John wiley and sons Publication.

Jacob J.L., Prevot J.C., Escnhach J.M., Lacrotte. R., Serres. E and A.Vidal (1991) Latex flow, cellular regeneration and yield of Hevea brasiliensis. Influence of hormonal stimulation. In proceedings of International congress of plant physiology (Eds. S.K.Sinha, P.V.Sane, S.C.Bharagava and P.K.Agrawal) volume-I, Page-420-435. Published by society for plant physiology and Biochemistry. WTC, Indian Agril. Research Institute, New Delhi-110 012.

Sethuraj M.R. (1991)- Physiological investigations on factors influencing productivity in Hevea brasiliensis. In proceedings of International Congress of Plant Physiology (Eds.S.K.Sinha, P.V.Sane, S.C.Bhargava and P.K.Agrawal). Volume-I, Page-398-403. Published by Society for Plant Physiology and Biochemistry. WTC, Indian Agril. Research Institute, New Delhi-110 012.