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The change in Global climate is due to increasing concentration of greenhouse gases (GHG) in the atmosphere. The earths' observed climatic changes over the past 50 years are primarily caused by various human activities. The increasing global temperature over the past century by about 0.8°C and expected to rise between 0.9 and 3.5°C by 2100. Such changes will not only have a great effect on the growth and cultivation of different crops but also affect the reproduction, spread and severity of many plant pathogens. Various plant disease models have been developed to incorporate more sophisticated climate predictions at various levels. At the level, the adaptive potential of plant and pathogen populations may prove to be one of the most important predictors of the magnitude of climate change effects. This review highlights various influences of climate change on plant diseases and their effects with suitable examples.

Rhizoctonia solani Kühn (Teleomorph: Thanatephorus cucumeris) is an economically important soil borne basidiomycetous pathogen of worldwide distribution. It causes sheath blight disease of rice and banded leaf and sheath blight (BLSB) disease in maize. Twenty three lowland rice weeds and thirty one upland (maize) weeds were collected and used. Rice isolate (SRS) was pathogenic on all the lowland rice and upland weeds. Maize isolate (RSM2) was not pathogenic on Cyperus difformis, C. haspans, C. odoratus, Sagittaria sagittifolia, Celosia argentea, Commelina diffusa and Floscopa scandens. Minimum days for scleriotia formation was 3 days on C. bengalensis, maximum sclerotia production was observed on Echinochloa crusgalli (14 nos.) with the isolate SRS. Minimum days for sclerotia formation was 2 days after inoculation on Euphorbia hirta, Fimbristylis dichotoma, Rotala indica and Scirpus juncoides. Maximum sclerotia production was observed on Alternanthera philoxeroides (11 nos.) with the isolate RSM2. Area under disease progress curve was calculated and mean separation was done using REGWQ test (Ryan/Elinot/Gabriel/Welsch procedure). The weeds Ageratum houstonianum (10.2), A. sessilis (14), A. philoxeroides (25.3), Imperata cylindrica (14), Paspalum distichum (17.8) and Ambrosia artemisiifolia (23.3) were susceptible whereas Dactyloctenium aegyptium (115.6), E. colona (115.6) and Bidens pilosa (111.9) were highly susceptible to the isolate SRS. The weed A. houstonianum (43.7) was susceptible and R. indica (267.4) and E. hirta (266.2) were highly susceptible to the isolate RSM2.

Development of transgenic plants by introducing defense genes is one of the strategies to engineer disease resistance. Transgenic ASD16 rice plants harbouring rice chitinase chi11 gene, belonging to a PR-3 group of defense gene conferring sheath blight (Rhizoctonia solani Kuhn) resistance, were used in this study. Three T 2 homozygous lines (ASD16-4-1-1, 5-1-1, and 6-1-1) were identified from seven putative (T 0 ) transgenic lines expressing chi11 using Western blotting analysis. The inheritance of sheath blight resistance in those lines was studied over generations. The stability of chi11 expression up to T 4 generation in all the three homozygous lines was proved by Western blot and the stability of sheath blight resistance in the homozygous lines was proved up to T 4 generation using detached leaf and intact leaf sheath assays. Among the three homozygous lines tested, ASD16-4-1-1 showed consistent results in all the generations and gave a better protection against the sheath blight pathogen than the other two lines.

Background: The main challenge confronting both rainfed and irrigated agriculture is to improve water use efficiency (WUE) and sustainable water use for agriculture. A field experiment was conducted during early summer season of 2020 to study the effect of drip irrigation combined with organic mulching on soil moisture, growth, yield of tomato grown on alfisols at the college farm of College of Agricultural Engineering, Madakasira, Ananthapuramu district of Andhra Pradesh. Methods: The experiment was laid out in completely randomized block design (CRBD) with seven treatments comprising of various organic mulches. The treatments were T1 - Sawdust + Irrigation based on daily crop water requirement, T2 - Ragi straw + Irrigation based on daily crop water requirement, T3 - Groundnut shells + Irrigation based on daily crop water requirement, T4 - Groundnut shells + Irrigation once in every two days, T5 - Saw dust + Irrigation once in every two days, T6 - Ragi straw + Irrigation once in every two days and T7 - Control (without mulch) + Irrigation based on daily crop water requirement. All the treatments were replicated thrice. The plot size of each treatment was 4m × 2.5m. Result: The results revealed that throughout the crop growth period, T3 - Groundnut shells + Irrigation based on daily water requirement maintained soil higher moisture content to an extent of 132-146% as compared to control T7 (Control + Daily water requirement). The fruit yield obtained with T3 - Groundnut shells + Irrigation based on daily water requirement was significantly higher (8.8 t/ha) as compared to control T7 (Control + Daily water requirement) (7.6 t/ha). The highest water use efficiency (39.6 kg/ha/mm) was noted with T4 - Groundnut shells + Irrigation once in every two days), whereas T7 (Control + Daily water requirement) registered minimum WUE (16.3 kg/ha/mm). Weed dry matter and weed index was found to be higher (50% to 100%) in T7 (Control + Daily water requirement) throughout the crop growth period as compared to all the treatments applied with organic mulches. Our results indicated that T3 - (Groundnut shells + Irrigation based on daily crop water requirement) resulted in the highest plant height, number of fruits per plant and high water use efficiency as compared to without mulching. Further, under irrigation water constraints, groundnut shells mulch and drip irrigation once in two days was found to be effective in attaining higher WUE.