We studied variations in water relations and drought response in five Himalayan tree species (Schima wallichii (DC.) Korth. (chilaune) and Castanopsis indica (Roxb.) Miq. (dhale katus) at an elevation of 1400 m, Quercus lanata Smith (banjh) and Rhododendron arboreum Smith (lali gurans) at 2020 m, and Quercus semecarpifolia Smith (khasru) at 2130 m) at Phulchowki Hill, Kathmandu, Nepal. Soil water potential at 15 (Psi(s15)) and 30 cm (Psi(s30)) depths, tree water potential at predawn (Psi(pd)) and midday (Psi(md)), and leaf conductance during the morning (g(wAM)) and afternoon (g(wPM)) were observed from December 1998 to April 2001, except during the monsoon months. There was significant variation among sites, species and months in Psi(pd), Psi(md), g(wAM) and g(wPM), and among months for all species for Psi(s15). Mean Psi(pd) and Psi(md) were lowest in Q. semecarpifolia (-0.40 and -1.18 MPa, respectively) and highest in S. wallichii (-0.20 and -0.63 MPa, respectively). The minimum Psi value for all species (-0.70 to -1.79 MPa) was observed in March 1999, after 4 months of unusually low rainfall. Some patterns of Psi(pd) were related to phenology and leaf damage. During leafing, Psi(pd) often increased. Mean g(wAM) and g(wPM) were highest in Q. semecarpifolia (172 and 190 mmol m(-2) s(-1), respectively) and lowest in C. indica (78 and 74 mmol m(-2) s(-1), respectively). Soil water potential (Psi) at 15 cm depth correlated with plant Psi in all species, but rarely with g(wAM) and not with g(wPM). Plant Psi declined with increasing elevation, whereas g(w) increased. As Psi(pd) declined, so did maximal g(w), but overall, g(w) was correlated with Psi(pd) only for R. arboreum. Schima wallichii maintained high Psi, with low stomatal conductance, as did Castanopsis indica, except that C. indica had low Psi during dry months. Rhododendron arboreum maintained high Psi(pd) and g(w), despite low soil Psi. Quercus lanata had low g(w) and low Psi(pd) in some months, but showed no correlation between tree Psi and g(w). Quercus semecarpifolia, which grows at the highest elevation, had low soil and plant Psi and high g(w).

In the central Himalaya, plants are subjected to a prolonged dry period, thus developing moisture stress. Variations in water relations and their response to drought in a Himalayan tree species, Schima wallichii at 1400 m elevation were studied at Phulchowki Hill, Kathmandu, Nepal. To understand the adaptational strategy of this species through which it withstands water stress, different parameters such as soil water potential at 15 (Y15) and 30 (Y30) cm depths, tree water potential at predawn (Ypd) and midday (Ymd), leaf conductance during morning (gw AM) and afternoon (gw PM) and correlation between all these variables were measured from December 1998 to April 2001, except during monsoon months. There was significant variation among months and years in Ypd, Ymd, AM and gwPM. Mean Ypd and Ymd were -0.20 and –0.63 MPa, respectively. The minimum Y value was observed in March 1999, after 4 months of unusually no rainfall. Some patterns of Ypd were related to phenology and leaf damage as Ypd often increased during leafing. Mean gw AM and gw PM were 95 and 75 m molm–2s–1, respectively. Schima wallichii maintained high Y, with low stomatal conductance reflecting its inherent dehydration postponement adaptation..Scientific World, Vol. 12, No. 12, September 2014, page 79-84

Bacterial blight disease of rice is a growing and challenging concern in Nepal. Since bacterial pathogen (Xanthomonas oryzae pv. oryzae) is difficult to manage by other means effectively, development of host plant resistance is the most effective mean to control this disease. This study was carried out to identify the bacterial leaf blight resistant genotypes of rice by using of molecular markers linked with bacterial blight resistant genes. Sixty genotypes of rice were screened at glass house for BB resistance and they were tested for the presence of Xa4, Xa5, Xa7 and Xa21 genes using markers MP, RM122, M5 and pTA248 respectively. IRBB 60 and Jumli Marshi were used as resistant and susceptible check respectively. Twenty five genotypes of rice were detected with presence of Xa4 gene, 24 genotypes with Xa5 gene and fourteen genotypes with Xa7 gene. Twenty four genotypes did not showed presence of any gene. Twenty four genotypes showed the presence of more than one gene with the specific molecular markers. Almost all genotypes that did not show presence of any gene were found highly susceptible in greenhouse conditions with both inoculums. Genotypes having more than one BB resistance gene were found resistant in greenhouse conditions with both inoculums suggesting combination of BB resistance gene through gene pyramiding will provide BB resistant varieties in rice breeding.

Five evergreen Himalayan trees namely Castanopsis indica, Schima wallichii, Rhododendron arboreum, Quercus lanata and Q. semecarpifolia were studied for their phenological responses to drought. Wood water properties (wood moisture percentage, wood density and water in wood per volume), starch percentage content, specific leaf mass, nitrogen content in leaves and phenological processes such as leaf emergence, senescence, flowering and fruiting were measured. Measurements were taken 28 times from December 1998 to April 2001 except for the monsoon months. There was significant variation in starch percentage in zero and one year old twigs. Mean starch percentage content ranged from 23% and 17.1% (S. wallichii) to 64% and 61.7% (C. indica) in zero year and one year old twig, respectively. Wood water properties were highest in R. arboreum and lowest in C. indica. SLM showed significant variation with sampled species and mean SLM was highest in R arboreum (1.6 × 10 -2 g cm -2 ) and lowest in S. wallichii (0.64 × 10 -2 g cm -2 ). Mean N ranged from 1.13% (R arboreum) to 1.98% (C. indica). Reserved starch percentage and SLM had a strong effect on phenological activities. They increased during the vegetative bud break and leaf emergence and decreased during senescence. Similarly, leaf nitrogen in the studied species was at the crest of concentration during leaf initiation then declined, one in expanded leaves as the concentration became diluted by increasing cell wall material, and the other at the time of senescence by resorption.

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